Predation and cannibalism of lady beetle eggs by adult lady beetles

The introduced lady beetle Harmonia axyridis now occurs across much of North America. This species is a strong intraguild competitor that may negatively impact local populations of native Coccinellidae. A laboratory examination of coccinellid egg predation, including cannibalism, revealed that eggs of two native species, Coleomegilla maculata and Olla v-nigrum, had significantly higher egg predation than did H. axyridis eggs. The addition of an alternative food source reduced egg cannibalism and predation. However, in the absence of an alternative food source, both native species attacked exotic eggs less than native eggs whereas, the exotic H. axyridis attacked all egg species similarly. This laboratory study shows that under conditions of low food availability, native coccinellid eggs would suffer from both cannibalism and predation whereas, cannibalism would be the larger threat to H. axyridis eggs.