Effect of prior diet on consumption and digestion of prey and non-prey food by adults of the generalist predator Coleomegilla maculata

Abstract

Insect omnivores may vary in their diets and digestion based on extrinsic and intrinsic factors, including gender and nutritional history. Here, we test two hypotheses involving an insect omnivore, Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae), feeding on prey [eggs of Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)] and non-prey [pollen of maize, Zea mays L. (Poaceae)] foods: (1) males and females consume different quantities of prey and non-prey food within a set period of time, and they digest these two foods at varying rates; and (2) dietary experience (prey vs. non-prey) affects the subsequent digestion of adults consuming these foods. Adults fed eggs or pollen did not ingest different quantities of food, although females consumed marginally more pollen than males, and males consumed marginally more eggs than females. Digestion rates, as measured by decline of quantitative PCR marker in the predators, were not significantly different for males and females, and corresponded to a quantitative half-life of 56 min for pollen and 46 min for eggs. But when newly eclosed females were fed with only prey for 7 days, they subsequently did not measurably digest non-prey food over 8 h, compared with females fed previously on pollen, which digested it with an estimated half-life of 45 min. Thus, feeding experience with some prey may cause changes in the digestive system of the predator, which later impair digestion of non-prey foods such as pollen by omnivores. This may have implications for survival and reproduction of omnivorous natural enemies released into the field or diet-switching associated with movement among habitats.