Submitted to: Encyclopedia of Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2008
Publication Date: 10/9/2008
Citation: Weber, D.C., Chaboo, C.S., Saska, P. 2008. Carabid beetles as parasitoids. Encyclopedia of Entomology. 2:35-37. Interpretive Summary: This review article describes beneficial beetles that are parasites of certain insect pests and kill the pest host in the process. Pests affected include elm leaf beetle and Colorado potato beetle. Knowledge of the life history of these beneficial insects can be used by other scientists interested in developing biological control methods as alternatives to reduce reliance on chemical pest controls.
Technical Abstract: The parasitoid habit is uncommon in beetles; only 11 beetle families include parasitoid species. Three tribes of 76 in the Carabidae are known to have species in which larvae are pupal ectoparasitoids: Brachinini, Peleciini, and Lebiini. The first larval instar is the free-living, host-finding stage; adults are predaceous in the host habitat with a narrow or broad prey range, which may include the larval host species. The best-known genera of parasitoid carabids are Brachinus, Lebia, and Lebistina. Brachinus emits a directed, explosive spray of boiling-hot quinone solution, the most highly evolved defensive secretion of the many documented in the Carabidae. Brachinus of North America inhabit freshwater littoral habitats, where beetle hosts in Hydrophilidae, Dytiscidae, and Gyrinidae, emerge to from the water to pupate. European Brachinus are associated with upland carabid hosts, Amara spp. Lebia adults typically seek prey in plant canopies; all 4 known larvae are ectoparasitoids of chrysomelid beetle pupae. Many additional Lebia species are associated as adults with specific chrysomelids, particularly Alticinae. Two species parasitize economically important hosts: L. scapularis on elm leaf beetle in Europe, and L. grandis on Colorado potato beetle in North America. Lebistina, an African genus closely related to Lebia, is one part of a complex anthro-ecological story involving arrow poison from pupae of the carabid and its chrysomelid host, which is used by the San indigenous tribe of Southern Africa to fell large game. Parasitoid carabids present some fascinating evolutionary questions, not the least of which is why both the impressive arrow-poisons and explosive exocrine toxins are associated with these genera. Yet at most 1% of their hosts are known. Management of beneficial predator/parasitoid beetles offers potentially valuable “double control” of chrysomelid pest species.