Prey selection behaviour in the multicoloured Asian ladybird, Harmonia axyridis (Coleoptera: Coccinellidae)

The multicoloured Asian ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is a generalist predator of aphids and other soft-bodied insects. Its diet leads to negative impacts on non-target species, despite its beneficial effects offered as biocontrol agent. Herein, we evaluated prey preferences and predation success of H. axyridis adults and 4th instar larvae exposed to binary prey combinations of insects commonly found in Italian vineyards. These binary combinations included a classic prey, Aphis craccivora (Hemiptera: Aphididae) and an alternative prey, i.e., first instar larvae of the European grapevine moth Lobesia botrana (Lepidoptera: Tortricidae), second instar larvae of H. axyridis, to evaluate cannibalistic behaviour of H. axyridis, fourth instar larvae of the non-target ladybird Scymnus apetzi (Coleoptera: Coccinellidae), to evaluate intra-guild predation. Results showed that H. axyridis larvae and adults can act as potential predators of the moth pest L. botrana. They were also able to predate the non-target coccinellid species S. apetzi, thus adversely affecting aphidophagous guilds. Harmonia axyridis larvae did not significantly prefer to predate A. craccivora over the other tested preys. Harmonia axyridis adults did not show significant preferences on A. craccivora over S. apetzi larvae, whereas they prefer A. craccivora over L. botrana and H. axyridis larvae. As a general trend, the prey selection time was shorter in H. axyridis larvae, if compared to adults. Overall, our study adds basic knowledge to the prey location behaviour of H. axyridis larvae and adults, showing main differences in predation parameters of larvae and adults of this species evaluating selected binary combinations of potential preys.