Egg production in response to combined alternative foods by the predator Coccinella transversalis

Insect predators may commit to reproduction to varying degrees depending on the nature of the prey they consume. I compared egg production by females of the aphidophagous ladybird beetle Coccinella transversalis (F.) (Coccinellidae) maintained on differing diets. As expected, females laid most eggs on a diet of aphids (pea aphids, Acyrthosiphon pisum[Harris]). Upon being switched from a diet of aphids, females laid no eggs after the first 3 days when maintained on a water solution of sucrose, and laid almost no eggs when maintained on a diet of second-instar larvae of the moth Helicoverpa armigera (Hubner). However, females laid eggs in small numbers (on average, 2.7 eggs per day) when provided both sucrose and Helicoverpa larvae. Females laid similar numbers of eggs when aphid honeydew was substituted for sucrose in combination with Helicoverpa larvae; in both cases, egg production was only 10-15% of that on a diet of aphids. The production of small numbers of eggs from consumption of non-aphid foods may enhance the ability of aphidophagous ladybirds to optimize their timing of reproduction at short-lived colonies of their preferred aphid prey.