Introduction: Acythopeus burkhartorum O’Brien is a petiole and tendril galling weevil. To control ivy gourd, Coccinia grandis (L.) Voigt three natural enemies, Melittia oedipus Oberthur [Lepidoptera: Sesiidae], Acythopeus cocciniae O’Brien (Curculionidae) and A. burkhartorum O’Brien were introduced to the Hawaiian Islands from East Africa. These natural enemies are being cultured at the Quarantine Laboratory in Guam" (PIER, 2003). In Hawaii two species of weevils have been released for biological control (Thomas, 1998). Some regions, including Hawaii, are experimenting with biological control of C. grandis primarily using A. burkhartorum and A. cocciniae, two nonindigenous weevils, to control infestations of ivy gourd (Thomas, 1998). The species were described from the coast of Kenya between Mombasa and Tanzania (O’Brien and Pakaluk, 1998).

Adults live up to 23 months and feed on the leaves causing holes in the leaves. Eggs are laid singly by inserting them in the young petioles or tendrils. Eggs hatch in about a week and larval development takes about three weeks. Pupation takes place within the gall and lasts for three to four months. Adult feeding on the leaves and larval galling of petioles and tendrils can cause drying of the leaves and eventual defoliation of vines (Murai et al., 1998). Currently the species is under investigation by the USDA for a possible release in Guam and Northern Mariana Islands for biological control of ivy gourd (USDA, 2004). A. burkhartorum has been field released in Guam in October 2004 and in Saipan in February 2005. Its field establishment in Guam on ivy gourd has been confirmed and its establishment in Saipan is yet to be verified (Reddy and Muniappan, 2005).

Description: Adults of the ivy gourd stem gallmaker are small (> 2.0 mm < 4.5 mm long), broad-oval, reddish black to black, moderately convex weevils. The dense coarse punctures each have a recumbent scale, which does not conceal the finely reticulate somewhat shining body. The venter is equally punctate with similar scales. The rostrum is strongly curved and strongly punctate in the stout basal three fourths, and the apex is markedly attenuate and finely punctate. There are neither spots nor bands formed by the pale setae. The small pygidium is visible and vertical. The legs are moderately stout with the femora and most clavate (not strongly swollen) and unarmed. The tibiae are straight with a small, indistinct, apical, inner tooth.

Host Plant: Ivy gourd, Coccinia grandis (L.) Voigt

Bibliography:

Murai, K., M. Chan and T. Culliney. 1998. Host range studies of two African Acythopeus spp. (Coleoptera: Curculionidae), potential biocontrol agents of ivy gourd, Coccinia grandis (Cucurbitaceae). Plant Pest Control Branch, Hawaii Department of Agriculture. 19pp.

O'Brien, C.W. and J. Pakaluk. 1998. Two new species of Acythopeus Pascoe (Coleoptera: Curculionidae: Baridinae) from Coccinia grandis (L.) Voigt (Cucurbitaceae) in Kenya. Proceedings of the Entomological Society of Washington 100 (4): 764-774.

PIER (Pacific Island Ecosystems at Risk). 2003. Coccinia grandis. Summary: Ecology, synonyms, common names, distributions (Pacific as well as global), management and impact information. Available from: http://www.hear.org/pier/species/coccinia_grandis.htm [Accessed 2 August 2005].

Reddy, G.V.P. and R. N. Muniappan. 2005. Biological control of the ivy gourd, Coccinia grandis (Cucurbitaceae) in the Mariana Islands. Annual Meeting of Entomological Society of America. Oral presentation (18 December 2005), Fort Lauderdale, Florida.

Thomas, P.A, 1998. Ivy gourd. Hawaiian Ecosystems At Risk, (HEAR). Summary: Information on ivy gourd in Hawaii. Available from: http://www.hear.org/ivygourd/index.html [Accessed 2 August 2005].

USDA (United States Department of Agriculture). 2004. Field release of Acythopeus burkhartorum (Coleoptera: Curculionidae), a non-indigenous weevil for control of ivy gourd, Coccinia grandis (Cucurbitaceae), in Guam and Northern Mariana Islands. Environmental Assessment. USDA-APHIS, PPQ, Riverdale, MD. 12pp.

2. Acythopeus cocciniae O'Brien - “Ivy Gourd Leaf Miner”

Species diagnostic characters:

Size: Minute to small., < 2.0 mm to < 4.5 mm

Body shape: Narrow-oval

Predominant color (cuticle): Black

Predominant color (scales): Gray or white

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Ascending and visible in dorsal view

Leg color (cuticle): Black

Leg color (scales): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Sparse

Waterproof coating: Absent

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Acythopeus cocciniae O’Brien is a leaf-mining weevil, native to East Africa. The species was described from the coast of Kenya between Mombasa and Tanzania (O’Brien and Pakaluk, 1998). Adults live up to 200 days and feed on the leaves causing numerous holes in the lamina. Eggs are laid singly by insertion into the lamina of ivy gourd leaves. Eggs hatch in about eight days and larvae mine the leaves for nine to ten days. Pupation takes place within the mine and lasts for 15 days. Adult feeding and larval mining can cause drying of the leaves and eventual defoliation of the ivy gourd vines (USDA, 2003). O’Brien and Pakaluk (1998) reported that this insect occurs only on ivy gourd. Some regions, including Hawaii, are experimenting with biological control primarily using A. burkhartorum and A. cocciniae, two nonindigenous weevils, to control infestation of ivy gourd (Thomas, 1998). These biological control agents are being cultured at the Quarantine Laboratory in Guam (PIER, 2003).

Description: Adults of the ivy gourd leaf miner are minute to small (< 2.0 mm to < 4.5 mm long), narrow-oval, moderately convex weevils, black with several small white spots of circular scales. At the base of the thorax (when not worn away) are three small white spots formed by shinglelike oval scales. A large white spot is found on the side of the body between the thorax and elytra, visible even in dorsal view. The venter of the thorax is coarsely punctate, and each puncture has a large recumbent grayish white scale. The venter of the abdomen is very sparsely punctate, each puncture with a fine pale seta, and the surface is smooth and shining. The rostrum is strongly curved throughout and strongly punctate in the basal half. The apical half is moderately attenuate and moderately coarsely punctate. The very small pygidium is visible and vertical. The legs are moderately stout with the femora moderately swollen and unarmed. The tibiae have a small, rather distinct, apical, inner tooth.

Host Plant: Ivy gourd, Coccinia grandis (L.) Voigt

Bibliography:

O’Brien, C.W. and J. Pakaluk. 1998. Two new species of Acythopeus Pascoe (Coleoptera: Curculionidae: Baridinae) from Coccinia grandis (L.) Voigt (Cucurbitaceae) in Kenya. Proceedings of the Entomological Society of Washington, 100 (4): 764-774.

Thomas, P.A. 1998. Ivy gourd. Hawaiian Ecosystems At Risk, (HEAR). Summary: Information on ivy gourd in Hawaii. Available from: http://www.hear.org/ivygourd/index.html [Accessed 2 August 2005].

USDA (United States Department of Agriculture). 2003. Field release of Acythopeus cocciniae (Coleoptera: Curculionidae), a non-indigenous leaf-mining weevil for control of ivy gourd, Coccinia grandis (Cucurbitaceae), in Guam and Saipan. Environmental Assessment. USDA-APHIS, PPQ, Riverdale, MD. 16pp.

3. Bagous affinis Hustache - “Hydrilla Tuber Weevil”

Species diagnostic characters:

Size: Medium-sized., > 4.5 mm < 10.0 mm

Body shape: Elongate-oval

Predominant color (cuticle): Dark brown to black

Predominant color (scales): Brown

Rostral length: Moderately short

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Weakly raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Present

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Dark brown

Leg color (scales): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Heart shaped, apically emarginate

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Present

Type of waterproof coating: Clear

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Bagous affinis Hustache was originally described from India and Pakistan and was first released in Florida in 1987. Buckingham (1988) reported the release of B. affinis in south Florida in April 1987 by the United States Army Corps of Engineers in a preliminary effort to control hydrilla. The species failed to establish in Florida and Texas (Coombs et al., 2003). Eggs are roughly spherical with a creamy white color. Eggs are laid usually on dead vegetation on the ground, e.g. plant stems, moist wood, etc in areas with annual dry periods, separate from periods of inundation by flooding or heavy rains. Annual drawdowns of water can serve the same purpose. Each female can lay up to 650 eggs in her life time. Eggs hatch in 3-4 days, and emerging larvae can crawl and search for the underground tubers, which they enter to feed on and to take shelter after burrowing through the soil (PMIS, 2003). The larvae feed inside subterranean turions or tubers of Hydrilla verticillata (L.f.) Royle during low water conditions. This results in reduced sprouting of the tubers (Godfrey and Anderson, 1994). The host range of B. affinis was studied in a quarantine laboratory to determine if the weevil would be safe for release in the United States as a biological control agent. Thirty-nine plant species (20 families) were tested with larvae and feeding was observed on only six species. In India and Pakistan this weevil species was taken only on hydrilla even though some of the other tested plants were present (Buckingham and Bennett, 1996).

Description: Adults of the hydrilla tuber weevil are dark brown to black, occasionally gray in color, and have a relatively streamlined body. Body medium-sized (> 4.5 mm < 10.0 mm long), elongate-oval and robust. Rostrum moderately short, 0.83 × as long as pronotum. Head weakly convex, swelling beside eyes very weak; eyes moderately convex. Antennae inserted laterally at apical 1/3, scape long, slender and subclavate. Pronotum weakly transverse, 0.92 × as long as broad. Prosternal sulcus deep, broad, scarcely narrowed at apical constriction. Scutellum large. Elytra subparallel behind humeri. Meso- and metasternum with punctures not forming large concavities, mesosternal process large. Abdominal sternum 1 with median impression shallow, broad, basal only; convex in apical 2/3, not continued on sternum 2. Intraspecific variation: declivital calli (tubercles) of elytral interval 5 vary from moderately developed and subquadrate, to weak and scarcely evident; color varies from black and gray to brown and whitish tan (O’Brien and Pajni, 1989).

Host Plant: Hydrilla, Hydrilla verticillata (L.f.) Royle

Bibliography:

Buckingham, G.R. 1988. Reunion in Florida – Hydrilla, a weevil, and a fly. Aquatics 10: 19-25.

Buckingham, G.R. and C.A. Bennett. 1996. Host range studies with Bagous affinis (Coleoptera: Curculionidae) an Indian weevil that feeds on hydrilla tubers. Tektran, USDA-ARS.

Coombs, E., J. Balciunas and P. McEvoy. 2003. Current status in each state of all 100 agents approved for release in the continental USA. Biological control of invasive plants in the United States. Corvallis, OR., Oregon University Press.

Godfrey, K.E. and L.W.J. Anderson. 1994. Feeding by Bagous affinis (Coleoptera: Curculionidae) inhibits germination of hydrilla tubers. Florida Entomologist 77(4): 480-488.

O’Brien, C.W. and H.R. Pajni. 1989. Two Indian Bagous weevils (Coleoptera: Curculionidae), tuber feeders of Hydrilla verticillata (Hydrocharitaceae), one a potential biocontrol agent in Florida. Florida Entomologist 72: 462-468.

PMIS (Plant Management Information System). 2003. Noxious and nuisance plant information system, ver. 5.3. Developed by Cofrancesco et al., (Cds and Web based. Available from: http://el.erdc.usace.army.mil/pmis/ [Accessed 14 April 2006].

4. Bagous hydrillae O'Brien - “Hydrilla Stem Borer”

Species diagnostic characters:

Size: Small to medium-sized., > 2.0 mm to < 10.0 mm

Body shape: Elongate-oval

Predominant color (cuticle): Dark brown

Predominant color (scales): Brown mottled with tan and white

Rostral length: Moderately short

Rostral width: Moderately narrow

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Present

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black to reddish brown

Leg color (scales): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Heart shaped, apically emarginate

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Present

Type of waterproof coating: Earthen

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Bagous hydrillae O’Brien is native to Australia and was released first in the United States in Florida in 1991 (PMIS, 2003). The weevil has since been released at numerous sites in Florida and Texas (Center et al., 2000) but had failed to establish (Coombs et al., 2003). At the time of this writing (2006) no established populations have been confirmed. A number of experiments were conducted in South Florida to determine the growth and development of B. hydrillae on hydrilla (Wheeler and Center, 1997).

Adults can be found on growing submersed hydrilla as well as on pieces of hydrilla that wash up on the shoreline. Adults feed externally on leaf and stem tissues on drying or submersed hydrilla. Eggs are laid within stem tissues, usually at the leaf node (i.e. where the leaves attach). There are three larval instars, each lasting from 3 to 4 days. Larval feeding subsequently fragments the stem, which floats to the shoreline where the 3rd instar larvae exit and eventually pupate within the soil or drying hydrilla. Pupation usually takes place under relatively dry conditions. The pupa does not form any protective covering such as a cocoon and is therefore referred to as naked. The pupal period lasts in 3 to 4 days depending on appropriate temperature (PMIS, 2003). The life cycle of B. hydrillae requires 17-21 days. Adults spend daylight time below the surface of the water where they crawl about, feed, and oviposit on the hydrilla stems. They emerge from the water and usually fly at dusk. Adults can live 60-80 days (Center et al., 2000).

Description: Adults of the hydrilla stem borer are dark brown with a distinctly mottled appearance. The rostrum is moderately short, 0.83 × as long as the pronotum. The body is relatively slender, small to medium-sized (> 2.0 mm to < 10.0 mm long) elongate-oval and strongly covered with dense, granulate scales. The usual earthen coating may be absent in some recently emerged adult specimens. The antennae are inserted near the apical 1/4th of the rostrum. The sulcus of the prosternum is moderately broad, deep and biangulate. The combination of reddish brown antennal scape and funicle and that of the basal 1/2 of the femora and the complete tibiae and tarsi (especially the femoral color) is diagnostic for the species. In many individuals 2-4 pale spots can be seen towards the rear of the elytra.

Host Plant: Hydrilla, Hydrilla verticillata (L.f.) Royle.

Bibliography:

Center, T.D., F.A. Dray and V.V. Vandiver, Jr. 2000. Biological Control with Insects: The hydrilla stem weevil. SS AGR 138. Institute of Food and Agricultural Sciences, University of Florida. Revised May 2002. Available from: http://edis.ifas.ufl.edu [Accessed on 17 December 2002].

Wheeler, G.S. and T.D. Center. 1997. Growth and development of the biological control agent Bagous hydrillae as influenced by hydrilla (Hydrilla verticillata) stem quality. Biological Control 8 (1): 52-57.

5. Bangasternus fausti (Reitter) - “Seedhead Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Elongate-oval

Predominant color (cuticle): Brown

Predominant color (setae): Brown to white

Rostral length: Short

Rostral width: Broad

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black

Leg color (setae): Brown to white

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Present

Wax like coating: Absent

Introduction: Bangasternus fausti (Reitter) is native to northern Greece and was released in the United States in 1991 (Rees et al., 1996). The weevil has been established in a number of States including California, Colorado, Minnesota, Montana, Nebraska, Oregon, South Dakota, Utah, Washington, and Wyoming as part of a program to control spotted and diffuse knapweed (Centaurea stoebi Lam. [formerly maculosa] and C. diffusa Lam.) (Lang, 1997., Coombs et al., 2003). It is not known how B. fausti will interact with other seedhead infesting biological control agents. Early concerns about the potential of B. fausti displacing Urophora affinis [Diptera: Tephritidae] have yet to be realized. Under favorable conditions weevil density can increase dramatically allowing the collection of large numbers of weevils for redistribution. Adult weevils emerge from the seedheads as well as ground litter in May and early June. Oviposition may occur 1-2 weeks after adult emergence. Eggs are oval, yellowish, and covered with a black egg-cap. The eggs hatch in 8-12 days and the larvae then mine into the knapweed seedhead and begin feeding. Larvae are white, legless, C-shaped grubs with brown head capsules that reach a length of approximately 8 mm. Each larva tunnels into the stem or bur. After this, it tunnels into the seedhead and feeds. Larvae consume up to 95% of the seeds in a head (Rees et al., 1996). Pupation occurs inside the seedhead. Adults may be found feeding on spotted or diffuse knapweed foliage in the spring and in the summer on the flowers. The white pupae are found inside a cell in the seedhead. The period from egg to adult is about 32 days and species is univoltine.

Description: Adults of the seedhead weevil are small (> 2.0 mm < 4.5 mm long), mottled white or gray and brown with a short, cone shaped blunt snout that appears to have been cut off (Lang, 1997). It has a distinct pair of raised ridges in front of the fore coxae. Dorsal setae are bifid and suberect to recumbent. The two claws on each tarsus are asymmetrical, one of each shorter than the other.

Host Plants: Diffuse knapweed, Centaurea diffusa Lam.; spotted knapweed, C. stoebi Lam. (formerly maculosa); purple starthistle, C. calcitrapa L.; squarrose knapweed, C. squarrosa Roth; and yellow starthistle, C. solstitialis L.

Bibliography:

Lang, R.F. (1997). Bangasternus fausti. Biological control. A guide to natural enemies in North America, Cornell University. Available: http:www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/bangasternus_fausti.html [Accessed 2 August 2005].

Rees, et. al., (1996). Biological Control of Weeds in the West, Western Society of Weeds Science, in Cooperation With USDA ARS, MT Department of Ag, and MT State Univ., Color World Printers, Bozeman MT.

6. Bangasternus orientalis (Capiomont) - “Yellow Starthistle Bud Weevil”

Species diagnostic characters:

Size: Medium-sized., > 4.5 mm < 10.0 mm

Body shape: Elongate-oval

Predominant color (cuticle): Dark brown to black

Predominant color (setae): Yellowish to whitish

Rostral length: Short

Rostral width: Broad

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Reddish brown

Leg color (setae): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense, in bands of patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Present

Wax like coating: Absent

Introduction: Bangasternus orientalis (Capiomont) was imported from northern Greece (PMIS, 2003). It is native to southern Eurasia and the Mediterranean Basin. The weevil was first introduced in the United States in 1985 in California, Idaho, Oregon, and Washington and now is established in these States (Coombs et al., 2003). Adult weevils emerge from their overwintering sites in May and can be seen on yellow starthistle from May through early July. A female may lay up to 470 eggs, which are laid in spring to summer. The eggs are deposited on leaves or stems below the young unopened buds and are covered with a black tar-like secretion by the female. The female glues eggs to the leaf and the coating prevents desiccation. Larvae, after hatching burrow into the leaf and up to the developing bud. They feed on the developing seeds and tissue of the disk. Usually 40-60% of the seeds in a head are consumed (Maddox et al., 1991), however, seed destruction can range from 30-100% depending on the size of the head (Pitcairn, 1996). Pupation occurs within the seed heads in chambers formed from damaged and undamaged seeds. Adults exit from the pupal chambers in the heads in late summer and overwinter outside the host plant. The weevil has one generation per year. Adults can live approximately 2 months. The cooler climates including coastal, higher elevations and latitudes are unfavorable to this weevil.

Description: Adults of the yellow starthistle bud weevil are medium-sized (> 4.5 mm < 10.0 mm long) and are elongate-oval in shape. The adult color varies from dark brown to black with a reddish tinge. The adult body is usually covered with yellowish to whitish hairs, with a somewhat mottled appearance. The rostrum is straight, 1.6 to 1.9 times longer than wide and strongly constricted at the base. Antennae are attached near the middle of the rostrum, the scape is shorter than the funicle, and the club is distinct and is wide in the middle and narrow apically and basally. The pronotum and elytra are clothed with bifid setae. The prosternum has a pair of raised ridges in front of the fore coxae which form a deep groove for receiving the rostrum. Legs are thick, the femora are unarmed but the tibiae possess a minute apical spine. Two claws are present, one side shorter than the other. The center of the first abdominal segment is depressed somewhat in males, however, it is flat in females.

Host Plants: Yellow starthistle, Centaurea solstitialis L. Host plants are restricted to the closely related genera of Cardumcellus, Carthamus, and Centaurea.

Bibliography:

Maddox, D.M., D.B.Joley, A. Mayfield, and B.E. Mackey. 1991. Impact of Bangasternus orientalis (Coleoptera: Curculionidae) on achene production of Centaurea solstitialis (Asterales: Asteraceae) at a low and high elevation site in California. Environmental Entomology 20: 335-337.

Pitcairn, M. 1996. Yellow starthistle control methods: biological control. California Exotic Plant Council. Proceedings paper. 1-4.

7. Ceutorhynchus trimaculatus (Fabricius) - “Rosette Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Black

Predominant color (scales): White

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Ascending and visible in dorsal view

Leg color (cuticle): Dark brown

Leg color (setae): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Ceutorhynchus trimaculatus (Fabricius) is native to Europe and northern Africa (Bolt et al., 1980). This weevil was studied in depth as a candidate for biological control (Kok et al., 1982., Kok and McAvoy, 1983). The species can be employed against Italian thistle and other Carduus species in North America (Goeden, 1974). The weevil has been considered a pest of artichoke, safflower crops and also has been found to be a potential predator of flowers and seeds of Italian and slender thistles (Bolt et al., 1980; Kok et al., 1982). The species has one generation per year. Adults emerge at the end of April and feed on the leaves of new rosettes or mature plants for three to four weeks. At the end of May, adults enter the soil to aestivate. Adults gradually become active again in autumn and feed on the leaves of young rosettes. Oviposition starts in November and continues through March or April. Larvae feed gregariously by boring into leaf buds or growing tips, and moving down into the crown. Pupation occurs in the soil (Boldt and Campobasso, 1981; Kok and McAvoy, 1983)

Description: Adults of the rosette weevil are small (> 2.0 mm < 4.5 mm long) in size, stout, broad-oval, and black, with distinct maculae and vittae formed by coarse, elongate-oval white scales. The body is rather densely clothed with black, tan, and a few white, scale like setae and patches of imbricate, white scales. The thorax has a small, median, basal, white macula and the sides are white with a pair of large, anterior, dorsolateral, white maculae. The base of the thorax is broadly rounded and the apex is strongly narrowed. The dorsum has a pair of subacute, basolateral tubercles. The elytra are strongly striate (grooved) with subcontiguous, large, deep, strial punctures. The intervals are more or less flattened throughout, except on the declivity where they form a broad callus on intervals 3-8. At the basal third angling forward to just behind the scutellum, the white scales form an interrupted maculate vitta. A transverse white fascia is present in front of the declivity and merges with the white elytral apex. The rostrum is long, curved, narrowly cylindrical, coarsely punctured, and densely clothed with suberect coarse setae. The rostrum is sharply constricted basally at its attachment to the head. The antennae are dark brown to yellowish and the funicle is seven-segmented. The eyes are round and moderately convex, with a broad shallow depression between them on the frons. The prosternum is deeply, narrowly sulcate. The legs are stout with strongly clavate femora, each with a large acute tooth. The tibiae are stout, sinuate and possess a small apical tooth on the inner margin. The tarsi (feet) are wide with the third segment strongly bilobed. The tarsal claws are free, subapproximate and long.

Host Plants: Thistles, Carduus spp. and Cirsium spp.

Bibliography:

Boldt, P.E. and G. Campobasso. 1981. Biology of two weevils, Ceutorhynchus trimaculatus and Trichosirocalus horridus, on Carduus spp. in Europe. Environmental Entomology 10: 691-696.

Bolt, P.E., G. Campobasso, and E. Colonnelli. 1980. Paleartic distribution and host plants of Ceutorhynchus trimaculatus and Trichosirocalus horridus (Coleoptera: Curculionidae). Ann. Entomol. Soc. America 73: 694-698.

Goeden, R. 1974. Comparative survey of the phytophagous insect faunas of Italian thistle, Carduus pycnocephalus, in southern California and southern Europe relative to biological weed control. Environ. Entomol. 3: 464-474.

Kok, L.T. and T.J. McAvoy. 1983. Biological studies of Ceutorhynchus trimaculatus (Coleoptera: Curculionidae), a thistle rosette weevil. Canadian Entomologist 115: 927-932.

Kok, L., T.J. McAvoy, G. Johnson, and P. Dunn. 1982. Further studies on Ceutorhynchus trimaculatus F. as a candidate for the biological control of Carduus species. Crop Protection 1: 67-74.

8. Cyphocleonus achates (Fahraeus) - “Root Boring Weevil”

or “Knapweed Root Weevil”

Species diagnostic characters:

Size: Large., > 10.0 mm

Body shape: Elongate, broad-oval

Predominant color (cuticle): Black

Predominant color (setae): Strongly mottled, bicolored or tricolored

Rostral length: Moderately long

Rostral width: Broad

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Present

Pronotal depression orientation: Transverse

Elytral carina(e): Absent

Elytral tubercle(s): Present

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black

Leg color (setae): White

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Cyphocleonus achates (Fahraeus) is native to Austria, Greece, Hungary, and Romania. The first release of the weevil in the United States occurred in 1988 in Montana to control spotted and diffuse knapweed, Centaurea spp. (PMIS, 2003). Then, species was released in Arizona, California, Colorado, Idaho, Minnesota, Montana, Nebraska, Nevada, Oregon, South, Dakota, Utah, Washington, and Wyoming to control spotted and diffuse knapweed; and is established on Centaurea diffusa Lam. in Montana, Nevada, and Oregon, but failed to establish in California, Colorado, Wyoming and Washington. The species was also released to control Centaurea jaceae × nigra (L.) and Centaurea stoebi (Coombs et al., 2003). In Canada, the species is widely distributed in British Columbia on spotted and large diffuse knapweed plants (Harris, 2005).

Adults emerge from mid-July to early September with peak emergence at about mid-August. Adults spend most of their life (about 10 weeks) on the root crown, just below the surface. They climb up to the tops of plants on sunny, warm days in search of a mate. Larvae hatch in 10 to 12 days and begin to tunnel into the root’s central vascular tissue where they complete their development. Unlike other knapweed weevils, C. achates has four larval instars. By the fourth instar, larvae are large, white and C-shaped. Cyphocleonus achates overwinter as larvae in the root. Mature larvae cause a gall in the root giving the root a swollen appearance. They pupate in the gall during the onset of warmer spring temperatures. New adults appear after about two weeks of pupation by chewing their way out of the root gall. Evidence of larval damage is a wide tunnel, abundant frass, and a swollen root gall (caused by the third and fourth instars). The species has one generation per year (PMIS, 2003; Harris, 2005).

Description: Adults of the root boring weevil are large (> 10.0 mm long) in size, elongate, broad-oval with a distinct tan-brown and white, banded and spotted pattern on the thorax and elytra. The recumbent white scale like setae are much coarser and denser than the moderately coarse tan-brown setae. The white setae nearly or completely conceal the body, but the brown setae are less dense, and visible among them are flattened shining black tubercles. The rostrum is moderately long, broadly flattened and has two broad, deep, sublateral grooves on the basal two thirds. Three broad carinae are visible in this area. The apical third is flattened and densely punctate under the dense, white, scale like setae. The legs and venter are covered with dense, white, and a few brown, recumbent, scale like setae, mixed with some erect, fine setae. The eyes are broad-oval. The prosternum is not sulcate, but has a pair of swellings just in front of the coxae. The tibiae have a moderate-sized, inner, apical tooth. The tarsal claws are large, approximate, connate (basally fused), and symmetrical.

Host Plants: Diffuse knapweed, Centaurea diffusa Lam. and spotted knapweed, C. stoebi Lam. (formerly maculosa) and C. jaceae × nigra (L.).

Bibliography:

Harris, P. 2005. Classical biological control of weeds, established biological control agent. Cypocleonus achates (Fahr.). Root-core feeding weevil. Available from: http://res2.agr.ca/lethbridge/weedbio/agents/acypach_e.htm [Accessed on 17 April 2006).

9. Cyrtobagous salviniae Calder and Sands - “Salvinia Weevil”

Species diagnostic characters:

Size: Minute to small., < 2.0 mm to < 4.5 mm

Body shape: Round-oval

Predominant color (cuticle): Black [in mature individuals]

Predominant color (cuticle): Brown [in teneral individuals]

Predominant color (scales): Metallic gold

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Present

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Reddish brown

Leg color (setae): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Linear

Vestiture type: Scales

Vestiture coverage: Sparse

Waterproof coating: Present

Type of waterproof coating: Clear

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Cyrtobagous salviniae Calder and Sands is native to South America, and was first reported in the United States by Kissinger in 1966 as Cyrtobagous singularis Hustache, the only species of the genus known at that time. The sibling species (C. salviniae) was described as a new species in 1985, and the different host association clearly demonstrated the reason for control of the weed in Australia following lack of control in Fiji (see Room, et al., 1981; Forno et al., 1983 and Calder and Sands, 1985 for a complete history of this problem). Biology of the weevil was studied in its native habitat of South America by Forno et al., 1983, who found that teneral adults are light brown when they first emerge, but as they mature they darken to black in 5 days. Adults are sub-aquatic and can be found beneath young leaves, within leaves or in the roots of Salvinia. Adults of this tribe, Stenopelmini, respire, when resting or feeding below the water surface, with the aid of air bubbles, a plastron (a specialized physical gill), or air trapped from plant stems. The preoviposition stage is 6-14 days. Eggs are laid singly in stem cavities made by the adult using its rostrum and apical mouthparts. Oviposition took place only when Salvinia was in contact with the water. Females laid one egg every 2-5 days over a 60 day study period. Larvae feed on young terminal buds and enter the leaf bud tunneling inside after 3-14 days of surface feeding. The average developmental time for larvae is 23 days at 25.5°C. Pupation takes place in a cocoon in contact with living plants. Most cocoons are found below the leaves or within the root mass.

Description: Adults of the salvinia weevil are minute to small (< 2.0 mm to < 4.5 mm long) in size, round-oval, shining black, and convex. The body is covered with a clear, shellac-like, waterproof coating through which the scattered, small, round, metallic gold, recumbent scales are clearly visible. The thorax lacks punctures. However, the elytra have large, very coarse, deep, strial punctures, which are broader than the convex elytral intervals. The rostrum is nearly straight and strongly swollen at, and in front of, the antennal insertion. The antennae and legs are reddish brown. The antennae are shining and glabrous basally, with only the apical half of the club setose. The inner surface of the femora and tibiae, the entire tarsi and the venter of the mesosternum, metasternum, and the basal two segments of the abdomen are completely covered with a grayish, velvet-like hydrofuge pubescence. The femora are moderately clavate, and the tibiae are nearly straight, with a minute (but visible) tooth on the inner apical surface. The tarsi are linear with the last segment longer than segments 1-4 together. The tarsal claws are free, approximate and very long.

Plant Hosts: Salvinia; Salvinia minima Baker, and S. molesta D.S. Mitchell.

Bibliography:

Calder, A.A. and D.P.A. Sands. 1985. A new Brazilian Cyrtobagous Hustache (Coleoptera: Curculionidae) introduced into Australia to control salvinia. J. Aust. Entomol. Soc. 24: 57-64.

Forno, I.W., D.P.A. Sands and W. Sexton. 1983. Distribution, biology and host specificity of Cyrtobagous singularis Hustache (Coleoptera: Curculionidae) for biological control of Salvinia molesta. Bull. Ent. Res. 73: 89-95.

Room, P.M., I.W. Forno and M.F.J. Taylor. 1984. Establishment in Australia of two insects for biological control of the floating weed Salvinia molesta. Bull. Entomol. Res. 74: 505-516.

10. Euhrychiopsis lecontei (Dietz) - “Milfoil Weevil”

Species diagnostic characters:

Size: Minute to small., < 2.0 mm to < 4.5 mm

Body shape: Elongate, broad-oval

Predominant color (cuticle): Brown to black

Predominant color (scales): Strongly mottled, bicolored or tricolored

Rostral length: Short

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Ascending and visible in dorsal view

Leg color (cuticle): Orange

Leg color (scales): Gray

Leg color (setae): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Present

Type of waterproof coating: Clear

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Euhrychiopsis lecontei (Dietz) is a weevil endemic to North America (Newman et al., 1997). This aquatic weevil species is being used as a biological control agent for Eurasian watermilfoil, Myriophyllum spicatum L. Both adults and larvae feed on Eurasian watermilfoil. This genus is currently monotypic, since a second species, E. albertanus Brown, has been synonymized. The two species appeared to be very different externally, but a study showed that the external morphological differences were the result of a cline in color and size from east to west in the USA and Canada and that the male genitalia were identical in more than 20 populations studied (Tamayo, et al., 1999). The species is highly specific to watermilfoils. Of over 200 females tested with watermilfoils and other native plants, only 3 eggs were laid on nonwatermilfoils (Solarz and Newman, 1996). The weevil spends most of its time under water except when overwintering. Females lay eggs singly on the meristem of watermilfoil plants. The larvae feed on the meristem and burrow through the stem cortex (Newman et al., 1996). The development time at 70-75°F on Eurasian watermilfoil averaged 4 days for the egg stage, 13 days for the larval stage, and 10-13 days for the pupal stage (Sheldon and O’Bryan, 1996). In New England, this species takes about 30 days for development from egg to adult stage and there are three generations per summer. The adults of the third generation leave a lake in the fall and fly to overwinter in terrestrial leaf litter. In the spring the adults fly back to the lake where they mate, lay eggs and complete their life cycle. Because of its very small size, this species is difficult to detect, and the current range of the weevil in North America is not completely known. However, this species has been found in the United States in Connecticut, Illinois, Iowa, Massachusetts, Michigan, Minnesota, New York, Vermont, Washington, Wisconsin, and in Canada in Alberta, British Columbia, and Saskatchewan.

Description: Adults of the milfoil weevil are minute to small (< 2.0 to < 4.5 mm long) in size, brown to black (mottled with whitish or greenish to yellowish markings) and rather strongly convex. The body is covered with hydrofuge scales completely concealing the cuticle in most specimens. Typically, pale scales cover the suture and margins of the elytra, and the midline and margins of the thorax, and form various maculae on the rest of the elytra. Some western forms are nearly all black, with only a whitish median macula and whitish margins as well. The dorsum of the thorax is undulate and has a pair of lateromedian blunt processes behind the middle. The elytra are striate (grooved) with evenly convex intervals, but the strial punctures are often not visible due to the dense coating of scales. The rostrum is rather short, nearly straight, and broadly cylindrical, and coated with hydrofuge (satin like) scales except near the apex. The antennae are reddish yellow. The funicle is six segmented. The eyes are round and strongly bulging with the frons distinctly, broadly depressed between them. The prosternum is not sulcate. The legs are long with the femora unarmed and moderately expanded to the apex. The tibiae are nearly straight, apically expanding and lacking apical teeth. The tarsi are long, with long fine sparse setae (setae as long as or longer than the diameter of a tarsal segment). The last tarsal segment on the hind tarsi is longer than the second and third segments together. The tarsal claws are free, widely separated and moderately long.

Host Plants: Eurasian watermilfoil (Myriophyllum spicatum L.) and North American watermilfoils particularly northern watermilfoil (M. sibiricum = exalbescens).

Bibliography:

Newman, R.M., K.L. Holmberg, D.D. Biesboer and B.G. Penner. 1996. Effects of a potential biocontrol agent, Euhrychiopsis lecontei, on Eurasian watermilfoil in experimental tanks. Aquatic Botany 53: 131-150.

Sheldon, S.P. and L.M. O’Bryan. 1996. Life history of the weevil Euhrychiopsis lecontei, a potential biological control agent of Eurasian watermilfoil. Entomological News 107: 16-22.

Solarz, S.L. and R.M. Newman. 1996. Oviposition specificity and behavior of the watermilfoil specialist Euhrychiopsis lecontei. Oecologia 106: 337-344.

Tamayo, M., C.W. O’Brien, R.P. Creed Jr., C.E. Grue, and K. Hamel. 1999. Distribution and classification of aquatic weevils (Coleoptera: Curculionidae) in the genus Euhrychiopsis in Washington State. Entomological News 110: 103-112.

11. Eustenopus villosus (Boheman) - “Yellow Starthistle Hairy Weevil”

Species diagnostic characters:

Size: Medium-sized., > 4.5 mm < 10.0 mm

Body shape: Broadly oblong-oval

Predominant color (cuticle): Brown

Predominant color (setae): Brown to gray or white

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Brown

Leg color (setae): Brown to gray

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Present

Wax like coating: Absent

Introduction: Eustenopus villosus (Boheman) was introduced from Greece into California for the biological control of yellow starthistle by the USDA-ARS in 1990. The insect was established near Grass Valley (Nevada County) and Camino (El Dorado County) in 1990 and Atlas Peak (Napa County), Potter Valley (Mendocino County), and Round Mountain (Shasta County) in 1991 (Villegas, 2004). This species is also a proven successful biological control agent for yellow starthistle in Arizona, California, Idaho, Oregon, and Washington (Coombs et al., 2003). The species was established readily in most areas of California, however, preferred the hotter interior parts of the state over cooler climate (coastal, higher elevations and latitudes) (Woods, 1998). In addition, high moisture and humidity may also be unfavorable to this species.

The species has one generation per year, and adults overwinter in the organic matter and litter at the base of previous-year stands of yellow starthistle and emerge to feed on young and unopened buds as temperatures warm up in May and June. Unlike other yellow starthistle natural enemies, this damage can be very extensive and readily noticeable. The weevils mate on top of the buds and the females lay individual eggs inside feeding holes on the sides of mature buds from late May through July depending on the area in California (Villegas, 2004). In about three days eggs hatch and the larvae begin to feed on the developing seeds and receptacle tissues. After about two weeks, larvae pupate in the pupal chambers. In another two weeks adult emerge and feed on developing small flower heads.

Description: Adults of the yellow starthistle hairy weevil are medium-sized (> 4.5 mm < 10.0 mm long) and are broadly oblong-oval in shape. The body color is light brown immediately upon eclosion but turns dark brown later. The elytra and upper thorax are covered with very long erect to suberect hairs which give it a hairy or fuzzy appearance. There are two white stripes running along the entire length of the third and fourth intervals and an even broader stripe on the margins of the ninth and tenth intervals of the elytra. The snout is quite long, 2-3 mm in length and nearly straight to weakly curved. The antennae are attached near the middle of the snout, strongly elbowed, and distinctly clubbed. Males are smaller than females (PMIS, 2003).

Host Plant: Yellow starthistle, Centaurea solstitialis L.

Bibliography:

Villegas, B. 2004. Releases of the Hairy Weevil, Eustenopus villosus, in California During 2000. California Department of Food and Agriculture. Available from: http://www.cdfa.ca.gov/phpps/ipc/biocontrol/annuals/2000annual/2000-28-euvi-rels.htm [Access on 17 April 2006].

Woods, D.M. (Ed.). 1998. Biological Control Program Annual Summary, 1997. California Department of Food and Agriculture, Plant Health and Pest Prevention Services, Sacramento, California. 85pp.

12. Exapion fuscirostre (Fabricius) - “Seed Feeding Weevil”

[Type Species of Exapion]

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Elongate, Pear-shaped

Predominant color (cuticle): Black to reddish brown

Predominant color (setae): White

Rostral length: Moderately long

Rostral width: Slender

Antennal morphology: Straight

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Brown

Leg color (setae): Brown

Trochanteral shape and length: Rectangular and moderately long

Femoral armature: Unarmed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Scales like setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Exapion fuscirostre (Fabricius) was introduced from Italy to the United States in 1964 and has established in both coastal and Sierran broom (Julien, 1992). There are high populations of E. fuscirostre in the coastal mountains, however, only small populations survive on Sierran plants. This is probably due to mortality in pods exposed to high temperature (Julien, 1992). The seed feeding weevil is specific to scotch broom, Cytisus scoparius (L.) and will not feed or develop on French broom (Andres, 1979). The weevil has become established in California (widespread, > 50% of host range), Oregon (widespread, > 50% of host range), and Washington (limited in host range, recovered in < 50% of host range) (Coombs et al., 2003). Adults feed on stems, while larvae feed on developing seeds inside pods. Despite a 60% reduction in seed production at some sites, the weevil has a limited impact on scotch broom (Rees et al., 1996).

Description: Adults of the seed feeding weevil are small (> 2.0 mm < 4.5 mm long), elongate, pear-shaped, black to reddish brown, with pale reddish antennae. The tarsi are dark reddish black to black. The body is covered with coarse scale like setae. The primary dorsal color is brown to brassy brown, due to the moderately coarse setae. The elytra have a pair of broad white stripes of coarse scale like setae curving from the shoulders to the apex where they connect with broad lateral white marginal stripes. The pleural area of the thorax has similar white coarse scale like setae that also cover most of the underside. The eyes are large, strongly convex and bulge outward on the small head. The base of the thorax has a median elongate deep glabrous furrow, visible as a short black line. The weakly curved rostrum is moderately long in both sexes and is glabrous and shining black. The antennae are straight, and inserted basally on the sides of the strongly expanded rostrum. The legs are long and moderately slender. The femora are subclavate and the nearly straight tibiae are expanded markedly from the base to the widened apex, which lacks any evident teeth. The basal segment, of the hind tarsus of the male only, has a stout ventral tooth. The tarsal claws are free, widely separated, basally toothed and long.

Host Plant: Scotch broom, Cytisus scoparius (L.)

Bibliography:

Andres, L.A. 1979. Biological control ‑ will it solve the broom problem? Fremontia 7(3): 9‑11.

Julien, M.H. 1992. Biological control of weeds: A world catalogue of agents and their target weeds. C.A.B. International. Third Edition. CSIRO, ACIAR, Australia. 186pp.

Rees, N.E., P.C. Quimby, Jr., G.L. Piper, E.M. Coombs, C.E. Turner, N.R. Spencer, and L.V. Knutson, eds. 1996. Biological Control of Weeds in the West. Western Society of Weed Science, USDA/ARS, Montana Dept. Agric., Montana State University, Bozeman, MT.

13. Exapion ulicis (Forster) - “Gorse Seed Weevil”

Species diagnostic characters:

Size: Minute to small., < 2.0 mm to < 4.5 mm

Body shape: Broad, Pear-shaped

Predominant color (cuticle): Reddish black to black

Predominant color (setae): Whitish to golden

Rostral length: Moderately long

Rostral width: Slender

Antennal morphology: Straight

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black to reddish black

Leg color (setae): Gray

Trochanteral shape and length: Rectangular and moderately long

Femoral armature: Unarmed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Scale like setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Exapion ulicis (Forster) feeds only on gorse, Ulex europaeus L. The species was selected in the early 1920’s for research to determine its effectiveness as a biological control agent. In the United States, it was released in 1926, 1949, 1951, and 1952 but failed to establish. The gorse seed weevil was again brought into the United States in 1953 from France (Holloway and Huffaker, 1957). Establishment was finally successful after its release in Hawaii in 1953 (PMIS, 2003). Now this species is established in California (widespread, > 50% of host range), Oregon (widespread, > 50% of host range), Hawaii, and Washington (limited in host range < 50% of host range) (Coombs et al., 2003). The species tends to do better in open, sunny pastures and hillsides. Bronzing of foliage can be found during summer, and conspicuous holes in flowers are made by adults searching for oviposition sites. Females after chewing hole(s) lay eggs singly or in clusters of up to 20 inside young green gorse pods. Larvae are white, squat, legless grubs (2-5 mm long) with a very small, brown head. Pupae are found inside the seed pod, and the newly formed pupae are white. As the pupae develop further, their color generally changes to gray. Development from egg to adult takes approximately 16 weeks. The eggs take 4 weeks to hatch, the larvae take 6-8 weeks to pupation, and pupae take 4 weeks to complete development within the pods. The species is univoltine. When the pods are opened adult weevils are released to feed on the spines and flowers (Cowley, 1983), sometimes defoliating large plants. In California, the weevil has been successful only partially in controlling gorse (Amme, 1983).

Description: Adults of the gorse seed weevil are minute to small (< 2.0 mm to < 4.5 mm long), rather broad, pear-shaped, reddish black to black weevils, which are densely clothed with whitish to golden, often shining metallic, scale like setae. The primary color is grayish white at low magnification. The elytra appear to be striped due to the pale color of the setae on the broad intervals versus the blackish narrow stripes of the striae (grooves) and their punctures. The base of the thorax has a median small round shallow glabrous pit, which is scarcely visible among the dense scale like setae. The eyes are large, strongly convex and bulge outward on the relatively small head. The evenly curved, moderately long, male rostrum and very long, female rostrum are glabrous and shining black. The straight reddish brown antennae are inserted basally on the side of the moderately expanded rostrum. The front legs are pale reddish, while the other legs are dark colored with black femora and reddish black tibiae. The femora are strongly clavate, while the tibiae are nearly straight and expanded markedly from the base to the widened apex, which lacks any evident teeth. Male tarsi lack a ventral tooth. The tarsal claws are free, widely separated, basally toothed and moderately long.

Host Plant: Gorse, Ulex europaeus L.

Bibliography:

Amme, D. 1983. Gorse control at Jughandle State Reserve: resource restoration and development. Unpublished manuscript. The Nature Conservancy, California Field Office, 785 Market Street, 3rd Floor, San Francisco.

Cowley, J.M. 1983. Life cycle of Apion ulicis and gorse seed attack around Auckland, New Zealand. N.Z. J. Zool. 10: 83-86.

Holloway, J.K. and C.B. Huffaker. 1957. Establishment of the seed weevil, Apion ulicis for suppression of gorse in California. J. Econ. Entomol. 50: 498-499.

14. Gasteroclisus tricostatus (Thunberg)

Species diagnostic characters:

Size: Medium-sized., > 4.5 mm < 10.0 mm

Body shape: Elongate-oval

Predominant color (cuticle): Dark brown to black

Predominant color (scales): Strongly mottled, bicolored or tricolored

Predominant color (setae): Gray

Rostral length: Moderately long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Present

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Dark brown

Leg color (setae): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Scales and setae

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Present

Introduction: In the United States, the original colonies were brought in the quarantine in 1999 from Pietermaritzburg, South Africa, to control the serious weed pest, Madagascar ragwort, Senecio madagascariensis Poir. This distinctive weevil was reared in the quarantine for 2-3 years in Hawaii. The larvae develop in the stems of the host plant. The weevil was discarded in the quarantine because it was not successful in controlling the weed (Bernarr Kumashiro, pers. comm.). The weevil is regarded as a successful biological control agent of Madagascar ragwort in its native habitats in South Africa, therefore, further study is needed to know its biology, ecology and effectiveness under field conditions. Currently, the species is considered without a common name.

Description: Adults of this medium-sized (> 4.5 mm < 10.0 mm long) weevil are quite slender and elongate-oval. Freshly emerged and carefully handled specimens are coated with a dense wax like secretion, both orange-brown and white in places on the body. The pleural area of the prothorax is separated from the dorsum by a pair of angled longitudinal carinae separating them from each other. The pleural area is strongly impressed and visible in dorsal view and usually coated with a dense white colored wax-like secretion. The addition of a median longitudinal prothoracic carina to the two lateral carinae explains the specific name, tricostatus and these are not to be found on any other North American weevil species. The elytra are narrowed apically and these are produced as two widely separated variously acute processes.

Host Plant: Madagascar regwort, Senecio madagascariensis Poir.

15. Gymnetron antirrhini (Paykull) - “Seed-gall Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Black

Predominant color (setae): Brown

Rostral length: Moderately long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black

Leg color (setae): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Present

Wax like coating: Absent

Introduction: The native range of Gymnetron antirrhini Paykull extends from North Africa to the northern limit of yellow toadflax, Linaria vulgaris P.Mill., however, it is scarce in southwestern Europe. The species was accidentally introduced into North America after 1900, especially through infested ornamental plants. The species is established in Canada with apparently stable host preferences for narrow-leaved or broad-leaved dalmatian toadflax or yellow toadflax. A "strain" of G. antirrhini presumably more host-specific to dalmatian toadflax was approved for release in the United States in 1995. In Washington State the species was reported to be equally abundant on narrow-leaved dalmatian and yellow toadflax, but not on broad-leaved dalmatian toadflax. Broad-leaved dalmatian toadflax is attacked locally in Saskatchewan (Smith, 1959) and broad-leaved dalmatian toadflax populations of both weevils from Yugoslavia, released in 1993, are surviving in British Columbia. The yellow-toadflax population was released in Alberta and Saskatchewan in 1957 and is now established across Canada (Harris and Gassmann, 2005). The larvae develop inside the fruit, and adults feed on leaves, buds and stems. Harris (1961) concluded that G. antirrhini is the most important agent for biological control of Linaria vulgaris P.Mill. in the eastern provinces of Canada, British Columbia, and the northwestern United States.

Description: Adults of the seed-gall weevil are small (> 2.0 mm < 4.5 mm long) in size, broad-oval in shape, black in color with a strongly attenuate and weakly curved rostrum, The rostrum is nearly straight, but curved downward at the antennal insertion, due to the strong attenuation of the rostrum apicad of the insertion. The rostrum is 2/3 to 3/4 as long as the pronotum. The elytral striae are 1/2 to 2/3 as wide as the intervals. The femora are equal sized and each have a minute tooth. The eltra and prothorax are covered densely with mainly erect to suberect dark colored setae. Each egg is a flattish oval, 0.49 x 0.27 mm long and is inserted into a round hole and usually covered by a yellow secretion. Larvae are about 2-5 mm long, legless, and C-shaped when viewed from the side. They are creamy-white in color with a tan head capsule.

Host Plants: Snapdragon, Antirrhinum majus L.; lesser snapdragon, A. orontium L.; dwarf snapdragon, Chaenorrhinum minus., dalmatian toadflax, Linaria dalmatica L. Mill., L. genistifolia L., L. repens (L.) Miller, L. tourneforti (Poir); and yellow toadflax, L. vulgaris P.Mill.

Bibliography:

Harris, P. 1961. Control of toadflax by Brachypterolus pulicatius (L.) (Coleoptera: Nitidulidae) and Gymnetron antirrhini (Paykull.) (Coleoptera: Curculionidae) in Canada. Canadian Entomologist 93: 977-981.

Harris, P. and A. Gassmann. 2005. Classical biological control of weeds, established biocontrol agents. Gymnetron antirhini Paykull and G. netum Germar Seed-gall Weevils. Available from http://res2.agr.ca/lethbridge/weedbio/agents/agymnet_e.htm [Accessed 18 April 2006].

Smith, J.M. 1959. Notes on insects, especially Gymnetron spp. (Coleoptera: Curculionidae), associated with toadflax, Linaria vulgaris Mill. (Scrophulariaceae), in North America. Canadian Entomologist 91: 116-121.

16. Gymnetron linariae (Panzer) - “Root-gall Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Black

Predominant color (setae): Whitish gray

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black

Leg color (setae): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Gymnetron linariae (Panzer) which is native to Europe was approved for release in the United States in 1995 (Hansen, 1998). Several releases have been made in western Canada and the United States; small populations may be established in Canada, but only one confirmed establishment in Wyoming has been reported on Linaria genistifolia L. in the United States (Coombs et al., 2003). The species appears in late spring. After feeding for several weeks on toadflax shoots, adults mate and females oviposit on roots. Eggs are deposited singly in small pockets chewed (into the root tissue) by the female and covered with excrement. Most eggs are laid in the root crown area. After hatching, larvae feed inside galls formed on the roots and their development with three instars, takes two to three months. Also pupation occurs within the galls during summer. Newly emerged adults may remain within the galls and enter diapause, while others may emerge and feed on toadflax shoots for 7-14 days before returning to the soil to overwinter. There is one generation known to occur in a year (Jordan, 1994; Hansen, 1998).

Description: The adults of the root-gall weevil are small (> 2.0 mm < 4.5 mm long), with dark brown to pale brown tarsi and antennae. They have a strongly curved rostrum, clearly attenuate towards the apex and as long as the pronotum. The lack of erect setae readily separates this species from the other Gymnetron. It possesses only whitish gray, recumbent, scale like setae on the prothorax and elytra. The margins of the pronotum are strongly, unevenly rounded near the middle. The femora are moderately swollen and have a minute inner tooth, easily missed due to the coarse long scale like setae, which often conceal it. Larvae are small, legless, and C-shaped. They are creamy-white in color with a yellowish head capsule.

Host Plants: Yellow dalmatian, Linaria vulgaris P.Mill., dalmatian toadflax Linaria genistifolia L. (= L. dalmatica L.Mill.).

Bibliography:

Hansen, R. 1998. Gymnetron Linariae Panzer (Coleoptera: Curculionidae). USDA-APHIS-PPQ, Forestry Science Lab, Montana State University, MT. Available from http://www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/gymnetron_linariae.html [Accessed 18 April 2006].

Jordan, K. 1994. Gymnetron linariae. Panzer (Col., Curculionidae), a candidate for biological control of dalmatian and yellow toadflax in North America. Intl. Inst. of Biol. Control European Station Final Report. 37pp.

17. Gymnetron tetrum (Fabricius) - “Mullein Seed Head Weevil”

Species diagnostic characters:

Size: Small:. > 2.0 mm < 4.5 mm

Body shape: Broad, round-oval

Predominant color (cuticle): Black

Predominant color (setae): Brassy metallic

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black

Leg color (setae): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Present

Wax like coating: Absent

Introduction: Gymnetron tetrum (Fabricius) was in the United States before 1876 when it was reported from Pennsylvania as a European introduction by LeConte and Horn (O’Brien Pers. Comm.). Blatchley and Leng (1916) indicated its range from Canada and New England to Iowa, north of Georgia and Arkansas. The species has been reported in Montana, Washington, and California where it controls Verbascum thapsus L. and it has been accidentally introduced into western Canada. It feeds on the seeds and has been found effective in reducing seed production throughout its range. As an introduction, and movement by man, the weevil has no natural range in the New World. The larvae feed on seeds and other tissues in the seed capsules. Larvae are able to destroy all seeds in a capsule; however, usually not all seed capsules are infested. Gross and Werner (1978) reported that up to 50 percent of seeds may be destroyed by the larval feeding of this species. The species oviposits in the flowers, and thedeveloping larvae effectively destroy most of the seeds (Reinartz,1984). However, weevil activity is confined largely to the firstfew weeks of the flowering season. Weevils are primarily found on larger plants withina population.

Description: Adults of mullein seed head weevil are broad, round-oval and flattened above. They are small (> 2.0 mm < 4.5 mm long) in size. The erect and recumbent, dense pubescence nearly conceals the shining black body. The setae and scalelike setae often have a brassy metallic color. The rostrum is straight and very strongly attenuate, and nearly as long as or longer than the pronotum. The erect to suberect pubescence is equally dense on the basal half of the rostrum, the legs, and the underside of the body. The femur of the front leg is toothed strongly only in the males. The femora are strongly dilated and toothed.

Host Plant: Flannel mullein/common mullein/flannelplant, Verbascum thapsus L.

Bibliography:

Gross, K.L. and P.A. Werner. 1978. The biology of Canadian Weed. 28, Verbascum thapsus L. and V. blattaria L. Can. J. Plant Sci. 58: 401-413.

Reinartz, J.A. 1984. Life history variation of common mullein (Verbascum thapsus). I. Latitudinal differences in population dynamics and timing of reproduction. Journal of Ecology 72: 897–912.

18. Hadroplontus litura (Fabricius) - “Canadian Thistle Stem Weevil”

[Type Species of Hadroplontus]

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Dark gray

Predominant color (scales): White

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Present

Mesothoracic epipleuron: Ascending and visible in dorsal view

Leg color (cuticle): Dark brown

Leg color (scales): White

Leg color (setae): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Hadroplontus litura (Fabricius) is a stem boring weevil which is native to Atlantic Europe (southern France to southern Scandinavia), and was introduced to Canada in 1965 and to the United States in the early 1970s to control Canada thistle (Evans, 1993). The species is established in the provinces of Alberta, British Columbia, Nova Scotia, Ontario, and Saskatchewan (Harris, 2005). In California and Colorado it failed to establish on Cirsium arvense. However, it established in Idaho, Nebraska, North Dakota, Oregon, Virginia, Utah, Washington, and Wyoming (Coombs et al., 2003). One of the major constraints in the widespread use of this species as a biological control agent for Canada thistle was the inability to collect adults for mass redistribution. Females can lay a group of 1-5 eggs in small cavities in the leaf tissues or in the mid vein on the underside of the young leaf. Eggs are deposited from March or April until mid-May, generally until plants are about 5 cm tall, after this time the plant becomes undesirable for egg laying. Each female lays an average of 120 eggs, generally on the smaller younger shoots. The newly hatched larvae mine the tissues of the leaf toward the main vein. Older larvae mine the stem, root crown, and root. There are three larval instars. Larvae are whitish, grub-like, and pointed at the rear end. The larvae leave the plant at the end of the third instar to pupate in an oval cocoon of soil particles about 4-6 mm in diameter. Adults can be found in the field from August until the following May or June, and, in some areas, July. Adults overwinter in the soil litter and can even tolerate spring flooding. There is only one generation per year (PMIS, 2003). The weevils can be found in habitats with disturbed areas, where thistle density is high and not affected by grazing, mowing, flooding or even herbicides.

Description: Adults of the Canadian thistle stem weevil are small (> 2.0 mm < 4.5 mm long) in size. The underside is white and the back is dark gray with a yellowish white cross at the center of the wings. This and other disruptive white patterns make the weevil almost invisible on the soil (Harris, 2005). They have a long snout and a white haired T-shaped marking on their back which is quite prominent.

Host Plants: Canada thistle, Cirsium arvense (L.) Scop., and Carduus defloratus L.

Bibliography:

Evans, E.W. 1993. Biological control agents for Utah weeds: Ceutorhynchus litura, a stem-mining weevil of Canada thistle. Fact sheet No. 92. Utah State University, Extension Entomology. 1-4.

Harris, P. 2005. Classical biological control of weeds, established biological control agents. Hadroplontus litura F. Stem Weevil. Available from: http://res2.agr.ca/lethbridge/weedbio/agents/aceutlit_e.htm [Accessed 17 April 2006].

19. Heilipodus ventralis (Hustache) - “Argentine Root Boring Weevil”

Species diagnostic characters:

Size: Medium-sized to large., > 4.5 mm to > 10.0 mm

Body shape: Elongate-oval

Predominant color (cuticle): Dark brown

Predominant color (scales): Brown

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Present

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Reddish brown

Leg color (scales): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Heilipodus ventralis (Hustache) was named as a potential biological control agent of poisonous native weeds (perennial snakeweeds) of rangelands of the southern United States in the genus Gutierrezia (Cordo et al., 1999). These authors also recorded the life history and ecology of H. ventralis in Argentina and discussed its potential as a biological control agent for snakeweed in North America. Adult weevils emerge from the taproots in early summer and lay eggs mostly in the crown near the soil line. The larvae tunnel down to the taproots where they pupate. They may overwinter in the taproots of the snakeweed and pupate in the spring. A generation usually requires one year, however, some individuals probably require two growing seasons. No predators or parasitoids have been recorded on this species.

Heilipodus ventralis occurs in climatic zones of Argentina that they are very similar to much of the area infested by Gutierrezia in North America. This type of infestation apparently does not occur, or is rare, in northern Argentina, which is climatically more similar to the southern range of Gutierrezia in central and northern Mexico. Also, the northern area infested by Gutierrezia in Wyoming and Montana is colder than that of the most southern areas of Argentina where H. ventralis occurs (Chubut Province) (Cordo et al., 1999). H. ventralis would appear to have a reasonable chance for reducing the present abundance of snakeweeds in North America. Trials in quarantine at Temple, Texas showed that the insect was sufficiently host specific for introduction and it was released in New Mexico and Texas in May and August 1998.

Description: The adults of the Argentine root boring weevil are medium-sized to large (> 4.5 mm to > 10.0 mm long) in size. Males and females are very similar in shape, although females are usually a little larger than the males. Hustache (1938) described H. ventralis from Argentina and it is known only from Argentina and Paraguay (Wibmer and O’Brien, 1986). Adults are dark brown in color with white, yellow, and dark spots that make the insect inconspicuous in its habitat at the base of the host plants. The most obvious character for separating the sexes is the shape of the two tibial teeth of the forlegs; in the male, the proximal tooth is much shorter than the distal tooth; in the female, the difference in length of the tibial teeth is minimal. Also, the color of the leg (cuticle) is reddish brown and the color of scales on the leg is brown.

Host Plants: Perennial snakeweeds: Broom snakeweed, Gutierrezia sarothrae (Pursh) Britton; and Rusby, and sticky snakeweed, G. microcephala (De-Candolle).

Bibliography:

Cordo, H.A., C.J. DeLoach and D.H. Habeck. 1999. Biology of Heilipodus ventralis (Coleoptera: Curculionidae), an Argentine weevil for biological control of snakeweeds (Gutierrezia spp.) in the United States. Biological Control 15: 210-227.

Hustache, A. 1938. Curculionides nouveaux de l’ Amérique méridionale, que se trouvent dans le Deutsches Entomologisches Institut 3ieme note. Arb. Morph. Tax. Ent. Berlin-Dahlem, 5(4): 334-349.

Wibmer, G.J. and C.W. O’Brien. 1986. Annotated checklist of weevils (Curculionidae sensu lato) of South America (Coleoptera: Curculionoidea). Mem. Am. Entomol. Inst. 39: 563pp.

20. Hylobius transversovittatus (Goeze) - “Root-feeding Weevil”

Species diagnostic characters:

Size: Large., > 10.0 mm

Body shape: Elongate-oval

Predominant color (cuticle): Reddish black

Predominant color (scales): White

Predominant color (setae): Pale

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Present

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Reddish black

Leg color (setae): Pale

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Scales and setae

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Hylobius transversovittatus (Goeze) is native to Europe and was introduced in the United States in 1992 to control purple loosestrife (Malecki et al., 1993). This species has been released in numerous states in the United States (Coombs et al., 2003). After that, releases were made in Ohio, Indiana, Illinois, Iowa, Michigan, Wisconsin, South Dakota, Colorado and Montana. Colonization of this introduced species appears to have been successful (Blossey et al., 1994). Within two years after their release, 18 of the 19 releases in nine States and two Canadian Provinces showed initial establishment or colonization (Hight et al., 1995; Piper 1996). The species occurs in all purple loosestrife habitats, except for permanently flooded areas. Experiments have shown that adults and larvae can survive extended submergence depending on prevailing temperature. However, excessive flooding prevents access by the adult weevil and eventually kills developing larvae.

Most of the adults emerge in spring from soil or soil litter and are nocturnal. They usually feed on new leaves of purple loosestrife. Damaged leaves show symptoms of adult feeding on leaf edges. Peak activity is reported from June to August. Eggs are laid singly and each female can lay up to 200 eggs in her life span. A female can lay 1-3 eggs daily into the plant stem or near a root. After hatching, larvae start mining down to the roots where they feed on root tissues. Larval development is completed in 1-2 years. Mature larvae form a pupation chamber in the upper part of the root. Larvae can hibernate at different stages of maturity. Adults usually emerge between July and October and may live for several years (Kok et al., 1992; Malecki et al., 1991).

Description: Adults of the root-feeding weevil are large (> 10.0 mm long) in size, and are similar in appearance to Heilipodus, but are less convex above and have two distinct, undulate, transverse bands of white strap like scales on the back. The rest of the surface has much sparser, much finer scales and setae, which do not cover the reddish black body color. The body punctures, especially those on the thorax, are very coarse and very deep, and each puncture has either a strap like scale or more often a seta projecting from it. The rostrum is long and evenly curved. The femora of all legs have a strongly developed acute tooth and the tibiae have only a single, strong, inner, apical tooth.

Host Plant: Purple loosestrife, Lythrum salicaria L.

Bibliography:

Blossey, B., D. Schroeder, S.D. Hight and R.A. Malecki (1994). Host specificity and environmental impact of the weevil Hylobius transversovittatus, a biological control agent of purple loosestrife (Lythrum salicaria), Weed Sci. 42: 128-133.

Hight, S.D., B. Blossey, J. Laing and R. DeClerck-Floate. 1995. Establishment of insect biological control agents from Europe against Lythrum salicaria in North America. Environ. Entomol. 24: 967-977.

Kok, L.T., T.J. McAvoy, R.A. Malecki, S.D. Hight, J.J. Drea and J.R. Coulson. 1992. Host specificity tests of Hylobius transversovittatus Goeze (Coleoptera: Curculionidae), a potential biological control agent of purple loosestrife, Lythrum salicaria L. (Lythraceae). Biological Control 2: 1-8.

Malecki, R.A., B. Blossey, S.D. Hight, D. Schroeder, L.T. Kok and J.R. Coulson. 1993. Biological control of purple loosestrife: A case study for using insects as control agents, after rigorous screening, and for integrating release strategies with research. BioScience 43: 680-686.

Malecki, R.A., S.D. Hight, L.T. Kok, D. Schroeder and J.R. Coulson. 1991. Information for the preparation of an environmental assessment. Plant Protection and Quarantine, APHIS, USDA. 79pp.

Piper, G.L. 1996. Biological control of the wetlands weed purple loosestrife (Lythrum salicaria) in the Pacific northwestern United States. Hydrobiologia 34: 291-294.

21. Larinus curtus (Hochhut) - “Flower Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Black

Predominant color (setae): Gray, Metallic, bronzed

Rostral length: Moderately short

Rostral width: Broad

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Dark reddish brown

Leg color (setae): Gray to bronze

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Larinus curtus (Hochhut) was introduced from Greece into California, Idaho, Oregon, and Washington from 1992 to 1994 by the USDA-ARS for the biological control of yellow starthistle, Centaurea solstitialis (Villegas, 2004). The species is established in California, Idaho, Oregon, and Washington (Coombs et al., 2003). The insect likes to live in cool climates particularly at higher elevations and latitudes and near the coastal areas. This weevil oviposits inside open flowers of a yellow starthistle and the larvae feed directly on the seeds. A single larva can consume most of the seeds in the seedheads of yellow starthistle. Larval development may be completed in 17-20 days. Pupation occurs in damaged seeds and the pupal period is completed in 4-5 days. Adults feed on the plants from late June to early August. They overwinter away from their host plants. The species has one generation per year (PMIS, 2003).

Description: Adults of the flower weevil are small (> 2.0 mm < 4.5 mm long) in size. Adult-body with entire underside densely covered with multiradiate setae divided to their bases. Rostrum moderately short and stout, gradually widening from base to apex, coarsely rugose; frons with punctures merging in short sulci in places. Pronotum subconical, with sides in basal half nearly straight, moderately converging at the anterior. Anterior margin of pronotum behind eyes straight, not forming rounded prominences (postocular lobes). Elytra at base noticeably wider than pronotum, usually narrowing from base to apex. Pubescence of dorsal surface noticeably raised. Legs usually reddish brown, rarely femora black. Fore tibia lacking sharp granules on inner margin; in females, without large, very broad, nearly lobe-shaped prominence adjacent to the sharp, narrow and long mucro.

Host Plant: Yellow starthistle, Centaurea solstitialis L.

Bibliography:

Villegas, B. 2000. Releases of the flower weevil, Larinus curtus, for the biological control of yellow starthistle in California in 2000. CDFA Biological Program Annual Report 2000.

22. Larinus minutus Gyllenhal - “Seedhead Weevil”

Species diagnostic characters:

Size: Small to medium-sized., > 2.0 mm < 10.0 mm

Body shape: Broad-oval

Predominant color (cuticle): Black

Predominant color (setae): Gray

Rostral length: Moderately short

Rostral width: Moderately broad

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Pale reddish brown

Leg color (setae): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Larinus minutus Gyllenhal was proven to be host specific and was imported from Greece for release in the United States and Canada in 1991 (Lang, 1997). On diffuse knapweed, Centaurea diffusa Lam., the species is established in California, Colorado, Montana, Nebraska, Nevada, Oregon, Utah, Washington, and Wyoming while on squarrose knapweed, C. virgata Lam., the species is established in California and Utah (Coombs et al., 2003). This weevil species is considered to be the most impressive biological control agent against diffuse knapweed. The insect has a significant impact on the plant growth and density in the Pacific Northwest (Story and Piper, 2001).

Adults are strong fliers and disperse throughout the entire knapweed patch in several years. They spend the winter in plant litter within the knapweed patch. Adults are active in the field from May or June until August. Mating occurs continuously during this 11-week period. Adults feed on the leaves (including rosette leaves in the spring), outer stem tissue and flowers, prior to laying eggs (Lang, 1997). Eggs are deposited in the seedhead between the pappus hairs. Up to five eggs are clustered; the number of eggs laid per female ranges between 28 and 130. Eggs hatch three days later and the newly hatched larvae feed on the pappus hairs, then move downward to consume seeds, and partially the receptacle. Feeding lasts about four weeks as larvae go through three instars. The number of L. minutus larvae a seedhead can support depends on the size of the seedhead and the knapweed species. The larva constructs a pupal chamber (partly from seed coats) attached to the flower base and pupate there. New adults emerge and feed on foliage and flowers before moving to overwintering sites at the base of the plants.

Description: Adults of the seedhead weevil are small to medium-sized (> 2.0 mm < 10.0 mm long), black in color, have a moderately short robust snout and are a soft seed-feeder like the Terellia virens (Loew) [Diptera: Tephritidae] and Larinus obtusus. Eggs are elongate, yellow and are often clustered in the seedhead between pappus hairs. Larvae are typical white, legless, C-shaped grubs with brown head capsules which undergo through three larval instars and reach a length of approximately 8 mm. Pupae are about 6 mm long, and white, turning brown shortly before emergence and generally resemble the adult weevil. Tibiae are always reddish brown, usually light reddish brown; femora more or less infuscate but at least the middle and hind femora always are with a brownish tint. The underside of the head and postocular area are clothed with bi-and tri-radiate scales, sides of meso-and meta-thorax with numerous such scales. Legs covered with long semierect hair-like setae or hairs. Inner margin of the fore tibia in female with shorter obtuse or bifurcate tooth adjacent to and not more than half as long as mucro. The aedeagus has a membraneous, nonsclerotized dorsal surface. The body narrower, usually parallel-sided in middle part, and often more or less shining; the pronotum and elytra have longer, more strongly raised and uniform pubescence, often producing no distinct maculae on the elytra (Korotyaev, Pers. Comm.).

Host Plants: Spotted knapweed; Centaurea stoebi Lam. (formerly maculosa), diffuse knapweed, C. diffusa Lam., and squarrose knapweed, C. virgata Lam.

Bibliography:

Lang, R.F. 1997. USDA-APHIS-PPQ, Bozeman Biocontrol Facility, Forestry Sciences Laboratory, Montana State University, Bozeman, MT 59717. Available from: http://www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/larinus_minutus.html [Accessed 19 April 2006].

Story, J.M. and G.L. Piper. 2001. Status of biological control efforts against spotted and diffuse knapweed, 11-16pp. In L. Smith (ed.), the First International Knapweed Symposium of the Twenty-First Century, Idaho.

23. Larinus obtusus (Gyllenhal) - “Seedhead Weevil”

or “Blunt Knapweed Flower Weevil”

Species diagnostic characters:

Size: Small to medium-sized., > 2.0 mm < 10.0 mm

Body shape: Broad-oval

Predominant color (cuticle): Black

Predominant color (setae): Gray

Rostral length: Moderately long

Rostral width: Moderately broad

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black and brown

Leg color (scales): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Present

Introduction: (Gyllenhal) is native to Europe. It was approved as a biological control agent for release in the United States in 1993 (Lang, 1999) against spotted knapweed, Centaurea stoebi Lam. (formerly maculosa) and meadow knapweed, C. jacea × nigra L. On meadow knap weed, the species is established in Wyoming, Washington, Oregon, and Montana while on spotted knapweed, it is established in California and Oregon (Coombs et al., 2003).

Adults of this species spend winter in soil litter, at or near the base of plants. Overwintering adults appear at the end of May and reach peak population levels during early July. Adults feed heavily on the foliage and flowers prior to mating and laying eggs. Females oviposit among the inner florets of newly opened flower heads throughout their 5 to 6 month lifespan. Occasionally adults may hibernate a second time and live a second season. Eggs hatch in 3 to 6 days and larvae begin feeding on pappus hair and developing seeds. More than one larva can occupy a seedhead. Larvae develop through three instars over a 4 to 6 weeks period, pupating in chambers constructed from cemented seeds and pappus hairs (Norman et al., 1996). The pupal period generally lasts 9 days. Adults emerge in late July and early August through holes chewed in the tops of the pupal chambers and vigorously feed on foliage before moving to overwintering sites in the soil. The species has one generation per year.

Description: Adults of the seedhead weevil are small to medium-sized (> 2.0 mm < 10.0 mm long), black-gray in color, and with a prominent bulbous snout. The weevils newly emerged from the seedhead are lighter gray in color and have a yellowish wax-like coating, appearing and fuzzy on their setae and bodies. The older weevils lose this coating, turning darker and sometimes become completely black in appearance. It is a soft seed feeder. Eggs are yellowish, oval to round. Larvae are white, legless, C-shaped grubs with brown head capsules. Pupae are also white, they turn brown shortly before emergence. The femora and tibiae are black, occasionally apices of tibiae and femora reddish brown. Underside of entire body with simple hairs, all except head and postocular area without bi-or triradiate scales, and sides of thorax without or with few such scales. Legs covered with short recumbent or subrecumbent (on tibiae) hair-like scales. Inner margin of fore tibia in female with large, broad, irregular-shaped tooth adjacent to and 2/3 as long as mucro. The aedeagus with sclerotized dorsal area depressed along midline. Body more robust, often nearly oval, always matte; pronotum and elytra with short recumbent narrow seta like scales, elytra always with distinct mottled pattern.

Host Plants: Spotted knapweed, Centaurea stoebi (formerly maculosa)., and meadow knapweed, C. jacea × nigra L.

Bibliography:

Lang, R.F. 1999. Larinus obtusus (Coleoptera: Curculionidae). USDA-APHIS, PPQ. Bozeman Biological Control Facility. Forestry Science Laboratory, Montana State University. Available from: http://www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/larinus_obtusus.html [Accessed 20 April 2006].

Norman. R, et. al,. 1996. Biological Control of Weeds in the West, Western Society of Weed Science, in cooperation with USDA, ARS, Mt, Dept. of Ag, and Mt State Univ., Color World Printers, Mt, Fed.

24. Larinus planus (Fabricius) - “Canada Thistle Bud Weevil”

Species diagnostic characters:

Size: Medium-sized., > 4.5 mm < 10.0 mm

Body shape: Elongate-oval

Predominant color (cuticle): Black

Predominant color (setae): White

Rostral length: Moderately long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Dark brown

Leg color (setae): White

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Larinus planus (Fabricius) was accidentally introduced to the Northeastern United States from Europe and the flower-head weevil preferred feeding on Canada thistle, but also fed on native Cirsium species (McClay, 1990). However, this adventives species became established in the United States in the 1960s (White, 1972). It has been released in British Columbia (IPMnet News, 1995), and is being redistributed from the northeast into other ecoregions of the United States. Certain unexpected ecological effects of distributing this exotic weevil for biological control of Canada thistle have been discussed, including its preferred attack on native thistles (Louda and O’Brien, 2001). The species significantly reduces the seed production of an endangered native thistle in Colorado, which reproduces by seed, and has had relatively little effect on Canada thistle in the same area, which propagates equally well with rhizomes. (Louda and O’Brien, 2001). The weevil overwinters in the adult stage in soil litter. The females lay eggs by drilling a hole into the side of an unopened bud. Usually a single egg is laid in the hole, however, if more than one egg is laid only one larva can survive. Larvae feed on the seed tissues and other flower parts. Pupation occurs in a cocoon made inside the bud. Average egg to adult development in the field is 38 days.

Description: Adults of the Canada thistle bud weevil are medium-sized (> 4.5 mm < 10.0 mm long), elongate-oval with a moderately distinct, white and black, spotted pattern on the elytra, and white margins on the thorax, formed by moderately coarse recumbent white setae. The setae conceal the shining black body partially. The rostrum is moderately long, slender, and evenly, weakly curved. It is not dorsally flattened and is carinate, not sulcate. The eyes are broadly oval. The prosternum is not sulcate. The tibiae have a small, inner, apical tooth. The tarsal claws are large, approximate, connate (basally fused) and symmetrical.

Host Plants: Canada thistle, Cirsium arvense, C. palustre with occasional records from other small headed Cirsium spp., including endangered species, Carduus spp., Galactites spp., Serratula spp.

Bibliography:

IPMnet News. 1995. Consortium for International Crop Protection. Integrated Plant Protection Center, Oregon State University, Corvallis.

Louda, S.M. and C.W. O’Brien. 2001. Unexpected ecological effects of distributing the exotic weevil, Larinus planus (F.), for the biological control of Canada thistle. Conservation Biology 16: 717-727.

McClay, A.S. 1990. The potential of Larinus planus (Coleoptera: Curculionidae), an accidentally introduced insect in North America, for biological control of Cirsium arvense (Compositae). Proceedings of the VII International Symposium on Biological Control of Weeds, pp. 173-179. In E.S. Delfosse (ed.), Instituto Sperimentale per la Patologia Vegetale Ministero dell’ Agricoltura e delle Foreste.

White, J.C. 1972. A European Weevil, Larinus carlinae Oliver, collected in Maryland. Cooperative Economic Insect Report 22: 418pp.

25. Mecinus janthinus Germar - “Stem-boring Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Elongate-oval

Predominant color (cuticle): Metallic blue

Predominant color (setae): Bronze to gray

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black

Leg color (setae): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Sparse

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Mecinus janthinus Germar was approved for release in the United States in 1995-1996. Its native range extends from central and southern Europe to the former southern USSR (Hoffmann, 1959). Field releases have been made at sites in western Canada and the western United States (Coombs et al., 2003). The early results with M. janthinus on dalmatian toadflax are extremely encouraging. On dalmatian toadflax, Linaria genistifolia Mill., the weevil species is established in Colorado, Idaho, Montana, Oregon, Washington, and Wyoming while on yellow toadflax, L. vulgaris Mill, the species is established in Wyoming only (Coombs et al., 2003).

Adults usually emerge in late spring or early summer and feed on toadflax leaves and stems, and may live for several weeks to about a month. Females chew holes in toadflax and oviposit singly into each hole, with approximately 2-100 eggs per stem (DeClerck-Floate and Miller, 2002). The newly emerged larvae begin feeding within toadflax stems, creating tunnels that increase in size and length as the larvae mature. Wilted shoots can be observed resulting from larval feeding. Larval development is completed in about a month, and mature larvae construct a cell within the mined stem where pupation occurs. Pupal development is completed in several weeks. Adults remain within pupal cells and overwinter there. The species has one generation per year (Jeanneret and Schroeder, 1992).

Description: Adults of stem-boring weevil are small (> 2.0 mm < 4.5 mm long) in size, elongate-oval, very slender, and have a pronounced long strongly curved snout. The head, thorax and appendages are black, except for the brownish tarsi. The wing covers are metallic bluish with parallel sides. The front femur of the male is strongly toothed while that of the female is smooth. This small, elongate thin weevil is not likely to be confused with any other biological control agents (native species in North America). The typical legless larvae are creamy-white in color with a light-brown head capsule, and appear C-shaped when viewed from the side.

Host Plants: Dalmatian toadflax, Linaria genistifolia Mill. (formerly L. dalmatica Mill)., and yellow toadflax L. vulgaris Mill.

Bibliography:

DeClerck-Floate and V. Miller. 2002. Overwintering mortality of and host attack by the stem-boring weevil, Mecinus janthinus Germar, on dalmatian toadflax (Linaria dalmatica (L.) Mill) in western Canada. Biological Control 24: 65-74.

Hoffmann, A. 1959. Coléoptères (Curculionidae) (Tribu des Mecinni). Faune de France, 62. Lechevalier, Paris. 1264-1327.

Jeanneret, P. and D. Schroeder. 1992. Biology and host specificity of Mecinus janthinus Germar (Col.: Curculionidae), a candidate for the biological control of yellow and Dalmatian toadflax, Linaria vulgaris (L.) Mill. and Linaria dalmatica (L.) Mill. (Scrophulariaceae), in North America. Biocontrol Sci. and Technol. 2: 25-34.

26. Microlarinus lareynii J. Duval - “Puncturevine Seed Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Elongate-oval

Predominant color (cuticle): Reddish brown

Predominant color (setae): Gray

Rostral length: Short

Rostral width: Broad

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Brown

Leg color (setae): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Present

Wax like coating: Present

Introduction: Microlarinus lareynii J. Duval was released for the first time on pucturevines in the United States in 1961, after the weevils’ importation from Italy (Huffaker et al., 1983; PMIS, 2003). In the early summer months of the same year they were released in Clark County, Nevada, and Stanislaus County, California. Subsequent releases were carried out in Arizona, California, Colorado, Utah, and Washington. On puncturevine, Tribulus terrestris L., the weevil species is established in Arizona, California, Colorado, Florida, Kansas, Nebraska, Oklahoma, Oregon, Texas, and Utah while establishment failed in Idaho, Wyoming, and Washington (Coombs et al., 2003). Adult weevils overwinter in the debris near the host plants. Adults can be found on several non-host plant species, probably in search of water. After excavating a pit in the side of a seedpod, the female weevil oviposits in this pit, covering the eggs with a fecal cement to prevent desiccation. The larvae on eclosion bore into the seed, where they feed. Total time for the life cycle in summer is usually 22 days. Probably, there are three generations of this species in California (PMIS, 2003).

Description: Adults of the puncturevine seed weevil are similar to the puncturevine stem weevil. The adult is a small (> 2.0 mm < 4.5 mm long) reddish-brown weevil. The species can be distinguished by its broader elongate-oval shape, the broader less attenuate rostrum, and symmetrically round eyes. The body is clothed densely with fine erect setae and slightly coarse recumbent setae, which do not completely conceal the reddish-brown body color, except on the sides of the thorax and parts of the elytra. The apical lateral margins of the prothorax lack ocular lobes, and possess very strong postocular vibrissae (a cluster of long dense setae). The prosternum (underside with front legs) is not sulcate medially. The tarsal claws are small, connate (basally fused), approximate, and symmetrical.

Host Plants: Puncturevine, Tribulus terrestris L., and Jamaica feverplant, Tribulus cistoides L.

Bibliography:

Huffaker, C.B., J. Hamai and R.M. Nowierski. 1983. Biological control of puncturevine, Tribulus terrestris in California after twenty years of activity of introduced weevils. Entomophaga 28(4): 387-400.

27. Microlarinus lypriformis Wollaston - “Puncturevine Stem Weevil”

Species diagnostic characters:

Size: Minute., < 2.0 mm

Body shape: Elongate-oval

Predominant color (cuticle): Reddish brown

Predominant color (setae): Gray

Rostral length: Short

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Brown to black

Leg color (setae): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Present

Wax like coating: Present

Introduction: The puncturevine stem weevil, Microlarinus lypriformis Wollaston is a native of Europe. The first release of this species in 1961 in the United States was of specimens imported from Italy (Andres, 1978; PMIS, 2003). The subsequent releases were made in Nevada, California Arizona, Colorado, Utah, and Washington. On puncturevine, Tribulus terrestris L., the weevil is established in Arizona, California, Colorado, Florida, Kansas, Nevada, Nebraska, New Mexico, Oklahoma, Oregon, Texas, and Utah, however, no establishment occurred in Idaho, Wyoming, and Washington (Coombs et al., 2003). The weevils are widespread in most areas in which they have become established, although in colder climates or mountain areas the cold temperatures have prevented establishment which is favored by warm temperature in areas associated with mild winters. Eggs are laid in pits chewed in the root crowns and the stems. The larvae mine the stems and roots and are very similar to those of M. lareynii. They pupate in the stems. Adults emerge from the exit holes in the stems and root crowns, and feed on stems and leaves. There are a number of generations of this species in a year. Their biology on puncturevine was studied under laboratory and insectory conditions in California. The eggs hatch in 2 to 3 days. The young larvae tunnel directly into the pith, where they initially confine their feeding. As the larvae mature, they also feed on the vascular tissues and inner cortex. Larvae tunnel 1-12 cm during their development, which lasts 27-28 days. Pupation occurs in open tunnels or in cells enlarged from smaller tunnels. The pupal stage lasts 4-5 days. The adults emerge from circular holes chewed mainly in the upper surfaces of stems, branches and crowns (Kirkland and Goeden, 1978).

Description: Adults of the puncturevine stem weevil are similar to those of the puncturevine seed weevil. The puncturevine stem weevil can be distinguished by its minute size (< 2.0 mm long), more slender elongate-oval shape, the relatively slender distinctly attenuate rostrum, and narrower asymmetrical oval eyes. The body is densely clothed with fine erect setae and slightly coarse recumbent setae, which do not completely conceal the reddish brown body color, except on the sides of the thorax and much of the sides of the elytra. The apical lateral margins of the prothorax lack postocular lobes, and possess very long postocular vibrissae (a cluster of dense setae). The prosternum (underside with the front legs) is not sulcate medially. The tarsal claws are small, connate (basally fused), approximate, and symmetrical.

Host Plants: Puncturevine, Tribulus terrestris L., Jamaica feverplant, Tribulus cistoides L., and Kallstroemia spp.

Bibliography:

Andres, L.A. 1978. Biological control of puncturevine, Tribulus terrestris (Zygophyllaceae): post introduction collection records of Microlarinus spp. (Coleoptera: Curculionidae). Proceedings of the 4th International Symposium on Biological Control of Weeds, Gainesville, FL. 132-136.

Kirkland, R.L. and R.D. Goeden. 1978. Biology of Microlarinus lypriformis (Col.: Curculionidae) on puncturevine in southern California. Annals of Entomol. Soc. America 71(1): 65-69.

28. Mogulones cruciger (Herbst) - “Root-feeding Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Black

Predominant color (scales): Strongly mottled, bicolored or tricolored

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e):Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Present

Mesothoracic epipleuron: Ascending and visible in dorsal view

Leg color (cuticle): Dark Brown

Leg color (setae): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Mogulones cruciger (Herbst) was released in Canada in 1997 and is established in Alberta and British Columbia (DeClerck Floate and Harris, 2005). The species is native to Europe and North Africa. Permission for field release in the United States has not been granted due to concerns of the United States Fish and Wildlife Service regarding potential non-target effects of M. cruciger on rare and endangered Boraginaceae (Andreas and Schwarzlaender, 2004).

The eggs are laid in a cavity gnawed in the petiole of rosette leaves, in the petiole of stem leaves nearest the crown, and in the shoot base and in the root crown. After oviposition the female covers the cavity with frass. The larvae are white with a light brown head capsule and development is completed in three instars. The larvae consume all parts of the root, including the central core and root crown, and if this food is insufficient they may feed on any tissue of hound’s tongue. Full-grown larvae leave the roots and construct a pupal chamber from soil particles, in which they pupate. Pupation is completed within two weeks. Most of the adults emerge in the spring. Adults may live 12-14 months and sex ratio is almost equal. Most adults emerge in April-May. They later feed on the leaves and mate within 14 days (DeClerck-Floate and Harris, 2005).

Description: Adults of root-feeding weevil are small (> 2.0 mm < 4.5 mm long) in size, broad-oval in shape, black body and body scales are strongly mottled, bicolored or tricolored. The center of the wing covers has a white cross that gives the species its name (DeClerck-Floate and Harris, 2005).

Host Plants: Hound’s tongue, Cynoglossum officinale L., and C. cheirifolium L.

Bibliography:

Andreas E. J. and M. Schwarzlaender. 2004. Seven years after its release in Canada: Is it safe to introduce the houndstongue root weevil, Mogulones cruciger, in the United States? Talk Presented at the Entomological Society of America. Available from: http://esa.confex.com/esa/2004/techprogram/paper_17422.htm [Accessed 21 April 2006].

DeClerck-Floate R. and P. Harris. 2005. Classical biological control of weeds established biocontrol agent. Mogulones cruciger (Herbst), root feeding weevil. Available from: http://res2.agr.ca/lethbridge/weedbio/agents/amogcruc_e.htm [Accessed 21 April 2006].

29. Nanophyes marmoratus (Goeze) - “Flower Bud Weevil”

Species diagnostic characters:

Size: Minute to small., < 2.0 mm to < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Black and reddish yellow

Predominant color (setae): Strongly mottled, bicolored or tricolored

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Present

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Yellowish brown

Leg color (setae): Brown

Trochanteral shape and length: Rectangular and moderately long

Femoral armature: Unarmed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Moderately sparse, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Nanophyes marmoratus (Goeze) is widely distributed in Europe and Western Siberia. It was introduced from Germany, and first released in New York and Minnesota in 1994. In Canada, the species is established in Manitoba (Harris, 2005). In the United States, it is established in California, Colorado, Idaho, Michigan, Montana, New Jersey, New York, Oregon, and Washington (Coombs et al., 2003).

After hibernation adults begin feeding on the young leaves of small pre-flowering host plants. After flowering, adults move to the flower spikes and feed on the receptacle and ovaries of the developing flower buds (Blossey, 2002). These unopened flower buds are located primarily in the upper portion of the flower spike. Flower buds damaged by adult feeding are often aborted or excised. Eggs are deposited singly in the tip of unopened flower buds. A female may lay two eggs per day with 60-100 eggs in her life span (PMIS, 2003; Harris, 2005). A single larva develops in a flower bud where it consumes the stamens, petals and ovary. Most buds drop before larval development is complete, but development continues, even in water, as the buds float. Pupation occurs in the lower portion of the bud where a pupation chamber is constructed from frass that accumulated during larval feeding. The emerging adults feed on the leaves before beginning hibernation. There is only one generation per year (PMIS, 2003). The weevil prefers habitats without prolonged flooding for its development.

Description: Adults of the flower bud weevil are minute to small (< 2.0 mm to < 4.5 mm long), black with variously placed light colored patches, on the elytra and pronotum. The legs are yellowish brown, sometimes with black knees (apices of femora). Both sexes have a long, very slender, slightly curved snout. The elbowed antennae separate this genus from the Apioninae, the only other group which also possesses the rectangular moderately long trochanter.

Host Plants: Purple loosestrife, Lythrum salicaria L.

Bibliography:

Blossey, B. 2002. Purple loosestrife. In Biological Control of Invasive Plants in the Eastern United States. R.V. Driesche, B. Blossey, M. Hoddle, S. Lyon and R. Reardon (eds.). USDA, Forest Service. 149-157.

Harris, P. 2005. Classical biological control of weeds, established biocontrol agents. Nanophyes marmoratus (Goeze), flower feeding weevil. Available from: http://res2.agr.ca/lethbridge/weedbio/agents/ananmar_e.htm [Accessed 21 April 2006].

30. Neochetina bruchi Hustache - “Chevroned Waterhyacinth Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Gray to brown

Predominant color (scales): Brown

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Present

Elytral carina(e) position: Posterior half of elytra on sutural interval

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Cinnamon

Leg color (scales): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Present

Type of waterproof coating: Earthen

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Neochetina bruchi Hustache is native to South America. All members of this genus are semi-aquatic, spending much of their time on or in aquatic plants of the family Pontederiaceae. The chevroned waterhyacinth weevil was introduced in Florida in 1974 and was released in Alabama, California, Louisiana, and Texas in following years (PMIS, 2003) to control waterhyacinth, Eichhornia crassipes (Mart.) Solms.

Adult females chew holes in the lamina or petiole of the leaf and deposit a single egg in each hole. Eggs may be deposited around the edges of adult feeding scars. It has been reported that chevroned waterhyacinth weevils prefer to lay eggs in the tender central leaves or ligules surrounding the leaf bases. Eggs hatch within 7-10 days at 75°F. A single female may oviposit more than 400 eggs during her lifetime, with more than 90% of the eggs deposited within a single one-month period (Center et al., 2002; PMIS, 2003). Essentially, the larvae are "worm-like", bearing no legs or prolegs, with only small enlargements with setae (small hairs) where legs would be found normally. The larvae are usually white or cream-colored with a yellow-orange head. The larvae typically are found feeding within the bases of leaves and petioles, entering the apex of the stem, when mature, where they destroy the apical bud. Pupae are creamy white and are enclosed within a cocoon which is formed among the lateral rootlets below the water surface.

Description: Adults of the chevroned waterhyacinth weevil are small (> 2.0 mm < 4.5 mm long) in size, similar in appearance to the mottled waterhyacinth weevil, and can be distinguished from it by the color and pattern of scales on the wing covers (i.e. elytra). The chevroned waterhyacinth weevil is usually gray to brown with a distinct lighter brown to tan chevron (crescent-shaped marking) on the wing covers. Although the chevron can be seen distinctly in most individuals, it is absent in others. Therefore, the glabrous dark raised lines (sutural carinae) present on the elytra are used as a primary difference to separate the species. In the chevroned waterhyacinth weevil the lines are shorter in length and located behind the midline of the wing covers. Another subtle character is the nature of the shallow grooves or striae running the length of the elytra; for the mottled waterhyacinth weevil the striae are relatively "coarse" as opposed to the "fine" striae present on the chevroned waterhyacinth weevil. O’Brien (1976) revised the genus Neochetina and added three new species with all six species are included in the key to species.

Host Plant: Waterhyacinth, Eichhornia crassipes (Mart.) Solms.

Bibliography:

Center, T.D., M.P. Hill, H. Cordo and M.H. Julien. 2002. Waterhyacinth. In Biological Control of Invasive Plants in the Eastern United States. R.V. Driesche, B. Blossey, M. Hoddle, S. Lyon and R. Reardon (eds.). USDA, Forest Service. 41-64.

O’Brien, C.W. 1976. A taxonomic revision of the new world subaquatic genus Neochetina (Coleoptera: Curculionidae: Bagoini). Ann. Entomol. Soc. America 69: 165-174.

31. Neochetina eichhorniae Warner - “Mottled Waterhyacinth Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Gray-black

Predominant color (scales): Brown

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Present

Elytral carina(e) position: Anterior half of elytra on sutural interval

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Dark brown

Leg color (scales): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Present

Type of waterproof coating: Earthen

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Overseas surveys were conducted in South America in the 1960’s to identify organisms that feed on waterhyacinth, Eichhornia crassipes (Mart.) Solms. in its native range. Three agents were identified including two weevil species in the genus Neochetina. The mottled waterhyacinth weevil, Neochetina eichhorniae Warner, was introduced in Florida in 1972 and was released in Alabama, California, Louisiana, and Texas in the following few years (Perkins, 1973). Currently, the mottled waterhyacinth weevil is well distributed throughout most of the range of waterhyacinth in the United States (PMIS, 2003).

Studies in most of the United States showed that adults of this species are reproductive all year, without producing distinct generations. However, in Florida, females of this weevil undergo a reproductive quiescence during the winter. Reproduction may begin again, usually after the month of December. Eggs are laid singly in the leaf epidermis and hatch in 7-17 days, depending on temperature. A larva completes its development in 36-90 days and has three instars. Larvae feed and develop in the petioles. Pupation lasts for 7-9 days at 81°F (Center et al., 2002; PMIS, 2003). A generation is completed in 70-140 days, based on temperature, depending on the time of the year.

Description: Adults of the mottled waterhyacinth weevil are small (> 2.0 mm < 4.5 mm long) in size and are similar in appearance to the chevroned waterhyacinth weevil. The dark, widely distributed mottled appearance is in contrast to the chevroned waterhyacinth weevil, which, in most individuals, has a distinct, lighter brown to tan chevron (crescent-shaped marking) on the wing covers. The dark, glabrous, sutural, raised lines (short carinae) present on the elytra are used as a primary difference to separate the species. In the mottled waterhyacinth weevil, these lines are longer and located forward of the midline of the wing covers. Another subtle character is the nature of the shallow grooves or striae running the length of the elytra. In the chevroned waterhyacinth weevil, the striae are relatively "fine" as opposed to the "coarse" striae present on the mottled waterhyacinth weevil (O’Brien, 1976).

Host Plant: Waterhyacinth, Eichhornia crassipes (Mart.) Solms.

Bibliography:

O’Brien, C.W. A taxonomic revision of the new world subaquatic genus Neochetina. Annals of the Entomological Society of America 69(2): 165-174.

Perkins, B.D. 1973. Potential for waterhyacinth management with biological agents. Proc. Tall Timbers Conf. Ecol. Anim. Control Habitat Manage. 4: 53-64.

32. Neohydronomus affinis Hustache - “Waterlettuce Weevil”

Species diagnostic characters:

Size: Minute to small., < 2.0 mm to < 4.5 mm

Body shape: Elongate-oval

Predominant color (cuticle): Dark brown

Predominant color (scales): Strongly mottled, bicolored or tricolored

Rostral length: Moderately long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Brown

Leg color (scales): Strongly mottled, bicolored or tricolored

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Present

Type of waterproof coating: Earthen

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Neohydronomus affinis Hustache is native to South America. It was first released as a biological control agent of waterlettuce in Florida in 1987 (Coombs et al., 2003). It is being used presently for the management of waterlettuce populations in Florida, Louisiana, and Texas (PMIS, 2003), and is established in these states (Coombs et al., 2003). Waterlettuce weevils are weak fliers. The species superficially resembles a number of other small weevils feeding on aquatic plants, e.g. Stenopelmus sp., which has a 7 segmented funicle and Tanysphyrus sp., which has the claw segment of the tarsi not extended beyond the bilobed third segment. Adults can be found on any non-submerged portion of the waterlettuce plant. Usually, adults are found in the grooves on the underside of the leaves or within the spongy leaf tissue.

Female weevils lay cream-colored, sub-spherical eggs within a small hole (0.5 mm diameter) cut into the upper surface of the leaf near the leaf edge. Larvae are very minute, yellowish, relatively featureless grubs. The posterior end of the larva appears "cut-off" as though someone took a hatchet to it. The larvae commonly mine the leaves although sometimes they can be observed on the leaf surface (Dray and Center, 2003). Mines are seen more often in the thinner outer 1/3 of the waterlettuce leaf and are not nearly so obvious in the thicker central and basal portions of the leaf. Mature larvae are usually more than 3 mm long. Pupation occurs within the mine galleries created by the larvae.

Description: Adults of waterlettuce weevil are minute to small (< 2.0 mm to < 4.5 mm long) stout, covered loosely with scales that vary from whitish through blue-gray to brown. Some populations are unicolored, others are marked by one or smaller to large subtriangular spots on the anterior mid-dorsum of the elytra (often forming a "Smiley" face-like caricature). These weevils are weak fliers and superficially resemble a number of other small weevils feeding on aquatic plants, notably Stenopelmus sp. and Tanysphyrus sp., from which they can be distinguished on the basis of snout structure and appearance of the tarsal claws (O’Brien and Wibmer, 1989).

Host Plants: Waterlettuce, Pistia stratiotes L.

Bibliography:

Dray, A.F. and T.D. Center. 2002. Waterhyacinth. In Biological Control of Invasive Plants in the Eastern United States. R.V. Driesche, B. Blossey, M. Hoddle, S. Lyon and R. Reardon (eds.). USDA, Forest Service. 65-75.

O’Brien, C.W. and G.J. Wibmer. 1989. Revision of the Neotropical genus Neohydronomus Hustache (Coleoptera: Curculionidae). The Coleopts. Bull. 43: 291-304.

33. Omphalapion hookeri (Kirby) - “Seed-head Feeding Weevil”

Species diagnostic characters:

Size: Minute to small., < 2.0 mm to < 4.5 mm

Body shape: Pear-shaped

Predominant color (cuticle): Black, metallic blue

Predominant color (setae): Brassy metallic

Rostral length: Long

Rostral width: Slender

Antennal morphology: Straight

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Black

Leg color (setae): Brassy metallic

Trochanteral shape and length: Rectangular and moderately long

Femoral armature: Unarmed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Omphalapion hookeri (Kirby) (formerly Apion hookeri) is originally from Europe and was released against scentless chamomile, Matricaria perforate Mérat and was recovered at different localities in western Canada between 1992 and 1997 (Hinz and McClay, 2000). The species is established in British Columbia, Alberta, Saskatchewan, and Manitoba (McClay and DeClerck-Floate, 1999). Eggs are white, later turn brown, 0.4 × 0.3 mm long, and are laid in the tubular flowers. They are aggregated and preferentially laid in apical heads, which produce the most seeds. The eggs hatch in 5-12 days. Larvae feed in tubular florets and pupate in the seeds. Development takes 4-5 weeks. Pupation takes place in the seed chamber in a cell of chewed plant fragments. Adults emerge in 7-14 weeks. Newly emerged adults feed and mate in the Fall, however, there is no oviposition in this season. Males do not survive the winter. However, females resume feeding in the Spring. Oviposition is delayed until a week after the first flower buds appear in June. The species is univoltine in nature (Harris and McClay, 2005).

Description: Adults of seed-head feeding weevil are minute to small (< 2.0 mm < 4.5 mm) in size and pear-shaped. The species has a domed prothorax strongly medially rounded at the sides, a visibly tapered rostrum, protruding eyes and no wing cover pattern. Striae are relatively wide and deep, and the intervals are broad and coarsely shallowly punctuate. The setae are brassy metallic and rather fine. The male body color is brassy black and 1.6-2.0 mm long, while the female is metallic blue, blue-green or purple, although they may appear black if greased and ranges in size from 1.9-2.4 mm long. The larva is white, legless, curved and found in the seedheads.

Host Plants: Scentless chamomile Matricaria perforate Mérat, M. maritime L., Anthemis cotula L., A. arvensis L., and Chrysanthemum leucanthemum L.

Bibliography:

Harris, P. and A. McClay. 2005. Classical biological control of weeds, established biocontrol agents. Omphalapion hookeri Kirby, seed-head weevil. Available from: http://res2.agr.ca/lethbridge/weedbio/agents/aomphook_e.htm [Accessed 24 April 2006].

Hinz, H.L. and A. McClay. 2000. Ten years of scentless chamomile: prospects for the biological control of a weed of cultivated land. In Proceedings of the X International Symposium on Biological Control of Weeds 4-14 July 1999, N.R. Spencer (ed.), Montana State University, Montana. 537-550.

McClay, A. and R. DeClerck-Floate. 1999. Establishment and early effects of Omphalapion hookeri (Kirby) (Coleoptera: Apionidae) as a biological control agent for scentless chamomile, Matricaria perforata Mérat (Asteraceae). Biological Control 14: 85-95.

34. Oxyops vitiosa Pascoe - “Melaleuca Weevil”

Species diagnostic characters:

Size: Medium-sized., > 4.5 mm < 10.0 mm

Body shape: Broad-oval

Predominant color (cuticle): Dark brown to gray

Predominant color (scales): Pale gray

Rostral length: Short

Rostral width: Broad

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Present

Prothoracic tubercle(s): Absent

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Present

Elytra carina(e) position: Entire length of elytra

Elytral tubercle(s): Present

Elytral spicule(s): Present

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Brown

Leg color (scales): White

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Oxyops vitiosa Pascoe is native to Australia and was originally described from Queensland, in 1870. The tree, known as melaleuca or the paperbark tree, was imported from Australia in 1906 and later planted extensively to drain the Everglades. Specimens of this weevil species were field released at several sites in Florida in 1997 to control melaleuca, Melaleuca quinquenervia (Cavanilles) S.T. Blake. As of March 1998, eight populations had become established in South Florida (Coombs et al., 2003).

Adults feed, mate, and lay eggs on or near young leaves and subsequently cover them with feces. A single female can lay up to 500-1000 eggs in her life span (Cuda et al., 2004). Oviposition occurs mainly during the daylight hours from September to March in Florida (Center et al., 2000). The eggs hatch in 6-10 days. Larvae are "slug-like", covered with a slimy and oily exudate, and with feces which remains attached at the anus and strings out and often forms long coiled filaments. The oil and feces sequester poisons from the host plant, which help protect the larvae from predation. They feed externally on young leaves, which is very uncommon in weevils. When they are done feeding, mature larvae burrow into the soil to fashion an oily cell in which to pupate. The adult weevil emerges in 2-3 weeks and lives for up to 9 months. The life cycle from egg to adult is about 48 days.

Description: Adults of the melaleuca weevil are medium-sized (> 4.5 mm < 10.0 mm long), dark brown and gray, usually with a rather distinct, dark brown, quadrate macula in the middle of the back (elytra). The macula is actually the result of a decrease in both the size and density of the pale gray scales covering the body, exposing the darkened surface of the body in the area of the macula. Adults are broad-oval and stout bodied with a short broad snout, which is slightly longer than broad. They have four strongly developed and two weakly developed tubercles in a pair of lines on their back.

Host Plants: Melaleuca, paperbark tree, "the tree from hell", cajeput tree, (Melaleuca quinquenervia (Cavanilles) S.T. Blake.

Bibliography:

Center, T.D., T.K. Van, M.B. Rayachhetry, G.R. Buckingham, F.A. Dray, S. Wineriter, M.F. Purcell, and P.D. Pratt. 2000. Field colonization of the melaleuca snout beetle (Oxyops vitiosa) in south Florida. Biological Control 19: 112-123.

Cuda, J., S.A. Wineriter, G.R. Buckingham, T.D. Center and K.T. Gioeli. 2004. Melaleuca snout beetle. Available from: http://creatures.ifas.ufl.edu/beneficial/melaleuca_weevil.htm [Accessed 24 April 2006].

35. Phrydiuchus tau Warner - “Mediterranean Sage Root Crown Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Black

Predominant color (setae): Strongly mottled, bicolored or tricolored

Rostral length: Long

Rostral width: Moderately slender

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Present

Elytral spicule(s): Present

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Dark brown

Leg color (setae): Strongly mottled, bicolored or tricolored

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Absent

Wax like coating: Absent

Introduction: Phrydiuchus tau Warner is native to Europe and was introduced in Oregon in 1971 against Mediterranean sage, Salvia aethiopis L. The species is now established at several locations in California, Colorado, Idaho, and Oregon (Coombs et al., 2003). This weevil feeds on the roots and crown during its larval stage and on the foliage and flowering shoots during its adult stage. Plants are greatly weakened or die under heavy feeding. The insect is readily available for distribution, or may be collected at previously established locations. The species can be transferred to new sites in cool, dry, storage containers with ample food (Wilson et al., 1994). Establishment of the weevil is favored on warm, dry, southern exposed slopes. This weevil has been successful in some areas, but may be ineffective in others. Utilizing the weevil with good perennial grass management has shown the most success. The weevil will feed also on meadow sage, but with little effect on the plants.

Description: Adults of the Mediterranean sage root crown weevil are small (> 2.0 mm < 4.5 mm long), stout, broad-oval, black, covered with dense checkered patches of white, black and reddish setae. It has a large median white t-shaped mark at the base of the wing covers. The snout is long and moderately slender, often hidden from view in a groove on the underside of the body. The adult weevil is easily identified, by the characteristic white "T" on the back.

Host Plant: Mediterranean sage, Salvia aethiopis L.

Bibliography:

Wilson, L.M., J.P. McCaffrey, and C.E. Coombs. 1994. Biological control of Mediterranean sage. Collection and redistribution of the Mediterranean root crown weevil. Pacific Northwest Extension Bulletin 473.

36. Phytobius leucogaster (Marsham) - “Flower-eating Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Black, reddish brown

Predominant color (scales): Strongly mottled, bicolored or tricolored

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Present

Pronotal depression orientation: Longitudinal

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Ascending and visible in dorsal view

Leg color (cuticle): Brown to black

Leg color (scales): Strongly mottled, bicolored or tricolored

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Scales

Vestiture coverage: Dense and complete

Waterproof coating: Absent

Circular scales: Present

Erect setae: Absent

Wax like coating: Absent

Introduction: Phytobius leucogaster (Marsham) can be found in lakes pools and ditches and can tolerate brackish water. This species was recorded from spiked water-milfoil Myriophyllum spicatum L. and whorled water-milfoil M. verticillatum L. The flower-eating weevil has been reported from three distinct areas in North America. These include the northeastern United States (Connecticut, Massachusetts, New York, and Vermont), upper midwestern United States (Michigan, Minnesota, Wisconsin, Illinois, and Iowa), and western Canada/northwestern United States (Alberta, British Columbia, Idaho, Colorado, Saskatchewan, and Washington) (O'Brien and Wibmer 1982; Creed and Sheldon 1994). The weevil completes all life stages fully submersed and the larvae are stem miners. Very limited information is available on the biology of this species in the United States and Canada.

Description: Adults of the flower-eating weevil are small (> 2.0 mm < 4.5 mm long), moderately elongate, strongly broad-oval, black, and reddish brown, with one or a few small pale spots, on a black and brown hydrofuge (satin like) scale coating, which completely conceals the cuticle of the body. The body is convex and lacks evident setae. The thorax is truncate apically, with a pair of small acute tubercles, and has a pair of acute strongly developed lateral tubercles behind the middle. The dorsum is mainly black with a median, basal, sublinear, impressed, white spot and the side margins are white. The elytra are black and brown with a distinctive, postscutellar, sutural, white spot and often with a similar, subapical, sutural, white spot.

Host Plants: Spiked water-milfoil, Myriophyllum spicatum L., and whorled water-milfoil, M. verticillatum L.

Bibliography:

Creed, R.P. and S.P. Sheldon. 1994. Aquatic weevils (Coleoptera, Curculionidae) associated with northern watermilfoil (Myriophyllum sibiricum) in Alberta, Canada. Entomological News 105: 98-102.

O'Brien, C.W. and G.J. Wibmer. 1982. Annotated checklist of the weevils (Curculionidae sensu lato) of North America, Central America, and the West Indies (Coleoptera: Curculionidae). Mem. Am. Entomol. Inst. 34: 382pp.

37. Rhinocyllus conicus Frölich - “Flowerhead Weevil”

Species diagnostic characters:

Size: Medium-sized., > 4.5 mm < 10.0 mm

Body shape: Elongate-oval

Predominant color (cuticle): Black

Predominant color (setae): Strongly mottled, bicolored or tricolored

Rostral length: Short

Rostral width: Broad

Antennal morphology: Elbowed

Prothoracic collar: Not raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Absent

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Absent

Elytral spicule(s): Absent

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Dark brown

Leg color (setae): Gray

Trochanteral shape and length: Triangular and short

Femoral armature: Unarmed

Tibial armature of apices: All with spine

Third tarsus shape: Bilobed

Vestiture type: Setae

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Present

Wax like coating: Present

Introduction: Rhinocyllus conicus Frölich was introduced from Europe into California in the early 1970’s for biological control of weedy thistles (Turner et al., 1987) after its establishment on naturalized thistle in Canada. Since then it has been introduced and redistributed widely within North America to control Carduus nutans L., and less widely to control C. acanthoides L., C. crispus L., C. pycnocephalus L., and Silybum marianum (L.). The larvae of this weevil species feed primarily within the flowerheads of Carduus, Cirsium, Onoprodum, and Silybum thistles in the subtribe Carduinae (Zwölfer and Harris, 1984). This is an introduced weevil species that oviposits on the bracts of thistle heads and whose larvae feed in the receptacle, destroying the seed. In 1969 the weevil was released in Montana (Rees, 1977) and Virginia (Surles et al., 1974). The species is now well established in several states of the United States (Trumble and Kok, 1982; Roduner et al., 2003).

Each female lays 100 to 200 eggs on the bracts of thistle heads. Eggs hatch in 6 to 9 days and newly hatched larvae feed through the bracts into the receptacle. Developing larvae feed on the receptacle and the young seeds, reducing or preventing the production of viable seeds. There are four larval instars which together last about 4 to 6 weeks. Pupation occurs in a black oval cell inside the thistle head, and requires another 7 to 10 days. Adults emerge from seed heads in July and August in more northern locations and in June and July in Texas. They remain inactive during the summer and then hibernate through the winter. The following spring adults emerge from winter shelters to lay eggs on the developing buds. There is one generation per year.

Description: Adults of the flowerhead weevil are medium-sized (> 4.5 mm < 10.0 mm long). They are elongate-oval, with an indistinct spotted pattern of white, and non-descript brown, recumbent, fine to moderately coarse setae. At most, the setae only partially conceal the shining black body. The thorax and elytra are very densely, moderately coarsely punctuate and frequently covered with a yellowish wax-like exudation. The rostrum is short, very broad, and broadly sulcate, with the side margins of the sulcus subcarinately raised and has a fine, but evident, median, longitudinal carina. The eyes are very narrowly oval. The prosternum is not sulcate. The tibiae have a very small, inner, apical tooth. The tarsal claws are small, approximate, connate (basally fused) and symmetrical.

Host Plants: Carduus, Cirsium, Onoprodum, and Silybum thistles.

Bibliography:

Rees, N.E. 1977. Impact of Rhinocyllus conicus on thistles in southwestern Montana. Environ. Entomol. 6: 839-842.

Roduner, M., G. Cuperus, P. Mulder, J. Stritzke and M. Payton. 2003. Successful biological control of the musk thistle in Oklahoma using the musk thistle head weevil and the rosette weevil. Am. Entomol. 49: 112-120.

Trumble, J.T. and L.T. Kok. 1982. Integrated pest management techniques in thistle suppression in pastures of North America. Weed Res. 22: 345-359.

Turner, C.E., R.W. Pemberton and S.S. Rosenthal. 1987. Host utilization of native Cirsium thistles (Asteraceae) by the introduced weevil Rhinocyllus conicus (Coleoptera: Curculionidae) in California. Environ. Entomol. 16: 111-115.

Zwölfer, H., K.E. Frick and L.A. Andres. 1971. A study of the host plant relations of European members of the genus Larinus (Col.: Curculionidae). Common Wealth Institute of Biological Control Technical Bulletin 14: 97-143.

38. Trichosirocalus horridus (Panzer) - “Thistle Crown Weevil”

or “Musk Thistle Rosette Weevil”

Species diagnostic characters:

Size: Small., > 2.0 mm < 4.5 mm

Body shape: Broad-oval

Predominant color (cuticle): Reddish brown, black

Predominant color (scales): Gray

Predominant color (setae): Strongly mottled, bicolored or tricolored

Rostral length: Long

Rostral width: Slender

Antennal morphology: Elbowed

Prothoracic collar: Raised (side view)

Prothoracic carina(e): Absent

Prothoracic tubercle(s): Present

Pronotal depression: Absent

Elytral carina(e): Absent

Elytral tubercle(s): Present

Elytral spicule(s): Present

Mesothoracic epipleuron: Not ascending and not visible in dorsal view

Leg color (cuticle): Dark brown

Leg color (setae): Brown

Trochanteral shape and length: Triangular and short

Femoral armature: Toothed

Tibial armature of apices: All lack spine

Third tarsus shape: Bilobed

Vestiture type: Scales and setae

Vestiture coverage: Dense, in bands or patches

Waterproof coating: Absent

Circular scales: Absent

Erect setae: Present

Wax like coating: Present

Introduction: Trichosirocalus horridus (Panzer) is considered to be a native of south and central Europe. This species was introduced from Italy to the United States in 1970-1972 for quarantine testing. After testing, the species was approved for field use in 1974 to control musk thistle, Carduus nutans L. (Kok, 1986). The species is now established in several states from Virginia to Washington (Kok and Mays, 1991; Coombs et al., 2003). In Oregon, the species was released to control Italian plumeless thistle, Carduus pycnocephalus L. in 1994, however, the weevil did not establish (Coombs et al., 2003), but it did establish in Virginia. The species is likely to be the most effective biological control agent for the control of plumeless thistle in Ontario and Quebec and of nodding thistle in cool summer regions (Kok, 2002).

This winter-active weevil, which produces hundred of eggs per female, has great potential as a control agent of nodding (musk) thistle too. In spring newly emerged adults feed extensively for several weeks before seeking shelter in the ground litter. They remain in a state of rest for the majority of the summer. Mating starts in late summer and females deposit eggs by making punctures on the underside of the leaf, and along the midrib and primary veins. Eggs are deposited singly or in clusters of as many as 2000 per female. Incubation lasts 13 days. Upon emergence, larvae move down the petiole toward the growth point. They feed within the stem-root junction for 40-164 days, depending on temperature. Overwintering can occur in this stage. Larvae pupate in the soil next to the host root, with pupation lasting about 18 days. Adult usually emerge in late June and early July, start feeding on foliage briefly, and then aestivate for the remainder of the summer. They become active again in September until colder weather arrives.

Description: Adults of the thistle crown weevil are small (> 2.0 mm < 4.5 mm long), stout, broad-oval, and reddish brown and black, with indistinct maculate vittae (stripes) formed by a waxy coating on recumbent short-oval scales. The body is also covered moderately densely with scattered, long, erect, white, black, and reddish brown, scale like setae. The thorax has white transverse fasciae (transverse elongate marks) behind the apex and behind the middle, and a median, longitudinal, narrow vitta, all formed by moderately dense, white, short-oval, recumbent scales.

Host Plants: In Europe this weevil species attacks the genera Carduus, Cirsium, Silybum, and Onopordum, however, most frequently it feeds on Carduus nutans.

Bibliography:

Kok, L.T. 2002. Plumeless thistle (Curled thistle, Bristly thistle). In: Biological Control of Invasive Plants in the Eastern United States. USDA Forest Service Publication FHTET, (ed. Van Driesche R. et al., 2002). 413pp.

Kok, L.T. 1986. Impact of Trichosirocalus horridus (Coleoptera: Curculionidae) on Carduus thistles in pastures. Crop Protection 5: 214-217.

Kok, L.T and W.T. Mays. 1991. Successful biological control of plumless thistle, Carduus acanthoides L. [Campanulatae: Asteraceae (=Compositeae)], by Trichosirocalus horridus (Panzer) (Coleoptera: Curculionidae) in Virginia. Biological Control 1: 197-202.