FEEDING RESPONSES OF ADULT COLEOMEGILLA-MACULATA (COLEOPTERA, COCCINELLIDAE) TO EGGS OF COLORADO POTATO BEETLE (COLEOPTERA, CHRYSOMELIDAE) AND GREEN PEACH APHIDS (HOMOPTERA, APHIDIDAE)

Feeding responses that influence the effectiveness of a polyphagous endemic coccinellid, Coleomegilla maculata (DeGeer), for biological control of Colorado potato beetle, Leptinotarsa decemlineata (Say), in potato were examined in the laboratory. Consumption rate, functional response, prey preference, and the effect of alternate prey were studied for C. maculata adult females feeding upon eggs of Colorado potato beetle; Myzus persicae (Sulzer) and corn pollen were alternate food sources. C. maculata females continuously supplied with eggs attacked an average of 20.8 eggs per 48 h, and introduction of M. persicae significantly reduced but did not eliminate egg feeding. Females starved for 24 h showed a Type II functional response to egg density when offered 10-70 eggs per 24 h in small cages at 26 +/- 2-degrees-C. Data fit well to the Holling disk equation, which predicted maximum egg consumption of 31.5 eggs per 24 h. The functional response curve showed suppression of egg feeding at high egg densities when aphids were present as alternate prey, but no effect was evident at low egg densities. There was no change in functional response with corn pollen as the alternate food. When Colorado potato beetle eggs and aphids were available in equal numbers, females did not prefer either prey at low prey densities, but they preferred aphids over eggs at high densities. Eggs were an adequate (but not optimal) diet for larval development and adult oviposition relative to M. persicae or corn pollen. Some implications for ecology and effectiveness of C. maculata for control of Colorado potato beetle in potato are discussed.