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Aleochara bilineata
(Coleoptera: Staphylinidae)

The rove beetles are the largest North American beetle family. Most are predaceous, and they are common in organic matter. Aleochara bilineata as an adult is predaceous, but its larvae are parasitic.

Appearance

A. bilineata adults are glossy black with short coarse hairs and are about 5-6 mm long. They have very small, reddish-brown, inconspicuous forewings beneath which the membranous hindwings are elaborately folded. The forewings look like pads on the upper abdomen. The long abdomen is held aloft like a scorpion if the beetles are disturbed. Well-developed "jaws" cross in front of the head of both adults and larvae. Adults are active, strong fliers.

Eggs are oval, about 0.5 mm long and 0.4 mm wide, and are covered with a gelatin-like material which is pale green at first and turns darker after a few days. First instar larvae are pale brown, about 1.5 mm long, slender, segmented, and tapered toward the anterior. They have large heads. The parasitic second and third instar larvae are white, have rudimentary legs, and are found within the host puparium.

Habitat (Crops)

Cole crops, onions, turnips, radish, corn, and others.

Pests Attacked

Root maggot eggs, larvae, and pupae, especially the cabbage and onion maggot.

Life Cycle

A. bilineata overwinters as a first instar larva within a host puparium. Two days after mating, females begin laying tiny, whitish elliptical eggs--about 15 per day with an average of 700 per season. Eggs are deposited in the soil among the roots of root maggot-infested plants. Larvae hatch in about 5 to 10 days and actively search for root maggot puparia in the surrounding soil. The larva punctures the host puparium, enters, and begins feeding. The entire host pupa is consumed. Although two or more larvae may occasionally enter the same puparium, only one will survive to maturity.

A. bilineata pupates within the host puparium and emerges as an adult after 30 to 40 days. The overwintering larvae emerge in the second half of July, and the second generation emerges at the end of August or in early September. Adults live 40 to 60 days, and the life cycle, from egg to adult is about 6 weeks. There may be two generations per year.

Relative Effectiveness

A. bilineata adults may consume up to five root maggot larvae per day--a pair may destroy 1200 eggs and 130 larvae, and during their lifetime their offspring may parasitize several hundred pupae. Adults are cannibalistic, eating their own eggs and attacking other adults when food supplies are low.

Adult rove beetles may not emerge in spring until several weeks after the overwintering root maggot adults emerge. This is too late to suppress early season crop damage, although late season parasitism of cabbage maggot pupae may sometimes be as high as 90% to 95%. In one field study, parasitism ranged between 30% and 70%.

A. bilineata has been mass reared in the former Soviet Union, Europe, and Canada for control of root maggots. It may therefore be feasible to mass release adults at the beginning of the season to increase predation and parasitism of the first generation of root maggots.

Pesticide Susceptibility

Laboratory tests showed A. bilineata to be highly susceptible to pyrethroid insecticides. A strain of A. bilineata selected for tolerance to cyclodiene-type insecticides proved successful as a natural enemy of cabbage maggots in Canadian trials in the 1960's. In a 1980 field study, the insecticide chlorfenvinphos used in conjunction with A. bilineata successfully controlled cabbage maggots, although parasitism was reduced.

Conservation

Rove beetles are found under debris and rocks, near water, in compost and piles of decaying material, or in the crop canopy. The adults have been found in sweet corn tassels and silks late in the season. Hedgerows and shelter belts may provide protection for adult beetles.

Commercial Availability

Rove beetles are not yet commercially available from North American insectaries, although mass rearing techniques have been developed.

References

Colhoun, E.H. (1953) Notes on the stages and the biology of Baryodma ontarionis Casey (Coleoptera: Staphylinidae), a parasite of the cabbage maggot, Hylemya brassicae Bouché (Diptera: Anthomyiidae). Can. Entomol., 85: 1-8.

Finlayson, D.G., Mackenzie, J.R., and Campbell, C.J. (1980) Interactions of insecticides, a Carabid predator, a Staphylinid parasite, and cabbage maggots in cauliflower. Environ. Entomol., 9: 789-794.

Hoffmann, M.P. and Frodsham, A.C. (1993) Natural Enemies of Vegetable Insect Pests. Cooperative Extension, Cornell University, Ithaca, NY. 63 pp.

Read, D.C. (1962) Notes on the life history of Aleochara bilineata (Gyll.) (Coleoptera: Staphylinidae), and on its potential value as a control agent for the cabbage maggot, Hylemya brassicae (Bouché) (Diptera: Anthomyiidae). Can. Entomol., 94: 417-424.

Samsoe-Peterson, L. (1985) Laboratory tests to investigate the effects of pesticides on two beneficial arthropods: a predatory mite (Phytoseiulus persimilis) and a rove beetle (Aleochara bilineata). Pest. Sci., 16:321-331.

Whistlecraft, J.W., Harris, C.R., Tolman, J.H., and Tomlin, A.D. (1985) Mass-rearing techniques for Aleochara bilineata (Coleoptera: Staphylinidae). J. Econ. Entomol., 78: 995-997.

Wishart, G. (1957) Surveys of parasites of Hylemya spp. (Diptera: Anthomyiidae) that attack cruciferous crops in Canada. Can. Entomol., 89: 450-454.

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