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: Phoridae) (1.2% of sampled ants) were larger and had lower survival rates than similar non-parasitized foragers. Moreover, the size of parasitized ants was significantly correlated with the number of A. attophilus puparia and percentage of adult emergence. These results suggest that host size is important for the reproductive success of A. attophilus. Different from most ant-parasitizing phorids, A. attophilus exhibits a pre-oviposition behavior that involves walking towards the host and inspecting it, and this careful approach may be responsible for a relatively low percentage of parasitoid detection 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 workers (minima) were significantly higher on leaves visited by A. attophilus, but larger foragers showed no response to phorids. These results demonstrated that minima react to the presence of A. attophilus and suggest a defensive role of these ants against phorid parasitism.