FUNCTIONAL-RESPONSE OF COLEOMEGILLA-MACULATA (COLEOPTERA, COCCINELLIDAE) TO COLORADO POTATO BEETLE EGGS (COLEOPTERA, CHRYSOMELIDAE)

A comparative study of the functional response of Coleomegilla maculat a DeGeer (Coleoptera: Coccinellidae) fourth instars was conducted unde r laboratory, greenhouse, and field conditions. In the laboratory, ind ividual larvae were placed in 9-cm petri dishes for 24 h, with 1, 3, 5 , or 7 Colorado potato beetle (Leptinotarsa decemlineata [Say]) (Coleo ptera: Chrysomelidae) egg masses. Each egg mass was standardized at 15 eggs. In the greenhouse and field, C. maculata larvae were provided w ith an equivalent of 0.5 to 35 L. decemlineata egg masses/m(2) of pota to leaf. Fourth instars of C. maculata exhibited a type II functional response to L. decemlineata eggs under laboratory, greenhouse, and fie ld conditions. Predator search efficiency was inversely related with p rey density. The maximum mean attack rate (8.7 eggs) by C. maculata la rvae in the held was about half the mean attack rate in the laboratory (17.6 eggs) and greenhouse (20.1 eggs). The difference in prey densit y between the laboratory and held seems to have been a major contribut ing factor in determining the rate of predation, whereas differences i n environmental conditions (e.g., temperature and possible alternate f ood) may explain the differences observed in the predation rate in the greenhouse and field. (C) 1997 Academic Press.