Effect of temperature and intraspecific allometry on predation by two phenotypes of Harmonia axyridis Pallas (Coleoptera: Coccinellidae)

Harmonia axyridis Pallas is a highly polymorphic coccinellid with a wide geographic distribution. Genetic polymorphism seems to be the strategy adopted for facing different habitats at different times. Many modifications, such as body shape, body size, and elytral patterns, may be adaptive through imparting increased tolerance to adverse conditions. Previous studies evaluating differences in the light-colored aulica and dark colored nigra phenotypes found differences in biological performances at 20degreesC. However, whether the predatory activity of the different phenotypes changes under different temperatures remains unknown. Relative consumption rate and predation activity of fourth instars and adults of aulica and nigra phenotypes were compared at 10, 15, 20, 25, and 30degreesC. Our results showed that temperature is a limiting factor to larval and adult relative consumption rate. The thermal optimum of nigra adults was 3.7degreesC lower than that of aulica. Both larvae and adults of nigra were more stenothermic than aulica. Close to the upper limit of tolerance (30degreesC), predation activity of nigra adults was more affected than aulica. In larvae body size and shape could explain the differences observed, because aulica is significantly bigger than nigra and thus aulica presumably can better control beat exchange.