Trophic habits of Aethina tumida (Coleoptera: Nitidulidae): their adaptive significance and relevance to dispersal.

Aethina tumida Murray is an African native that has become an important pest of honey bee colonies in North America and Australia. Adults and larvae feed on pollen, honey, and brood in bee hives. The beetle is also able to feed and reproduce on fresh or rotting fruit, but natural occurrence on this diet has rarely been observed. We compared the reproductive success-as measured by progeny production, weight of progeny, developmental rate, and survival of immature stages-of beetles reared on various diets of fruit and bee products. Reproduction on all of the diets was sufficient for population growth. Using baited flight traps to monitor the presence of A. tumida, we found persistent although tenuous populations in wooded habitats lacking managed bee colonies. On the basis of these findings and the habits of other nitidulid beetles, we propose that A. tumida is an ecological generalist able to maintain adequate levels of reproduction in marginal environments but able to reach high levels in favorable, resource rich environments, such as honey bee colonies. This hypothesis has significance for active dispersal and range expansion, because reproduction in the absence of bees would facilitate long range dispersal by flight through successive generations. Although our findings support the hypothesis, definitive proof would require association of beetles with hosts, trapping adults as they emerge from the soil, or other methods that would confirm feeding and reproduction at a given site, rather than immigration from bee colonies.