Biology and oviposition behavior of the phorid Apocephalus attophilus and the response of its host, the leaf-cutting ant Atta laevigata

Atta laevigata (Smith) (Hymenoptera: Formicidae) foragers collected in the field and parasitized by Apocephalus attophilus Borgmeier (Diptera: Phorida e) (1.2% of sampled ants) were larger and had lower survival rates than sim ilar non-parasitized foragers. Moreover, the size of parasitized ants was s ignificantly correlated with the number of A. attophilus puparia and percen tage of adult emergence. These results suggest that host size is important for the reproductive success of A. attophilus. Different from most ant-para sitizing phorids, A. attophilus exhibits a pre-oviposition behavior that in volves walking towards the host and inspecting it, and this careful approac h may be responsible for a relatively low percentage of parasitoid detectio n by A. laevigata. When an exotic resource (Acalypha sp. leaves) was placed on ants' foraging trails, more foragers were recruited, which resulted in the attraction of A. attophilus. The number and recruiting rates of small w orkers (minima) were significantly higher on leaves visited by A. attophilu s, but larger foragers showed no response to phorids. These results demonst rated that minima react to the presence of A. attophilus and suggest a defe nsive role of these ants against phorid parasitism.