Oviposition behavior of an ant-parasitizing fly, Neodohrniphora curvinervis (Diptera: Phoridae), and defense behavior by its leaf-cutting ant host Atta cephalotes (Hymenoptera: Formicidae)

This study examines the oviposition behavior of the phorid parasitoid Neodohrniphora curvinervis and the antiparasitoid defense behavior of its leaf-cutting ant host Atta cephalotes. N. curvinervis females are diurnal sit-and-wait parasitoids that attack only outbound foragers of head width 1.6 mm or greater. Females deposit a single egg through the foramen magnum of each host successfully parasitized. Pursuit of hosts is usually initiated when an outbound forager of acceptable size passes by a parasitoid perch site. Individual foragers defend themselves against pursuing parasitoids by outrunning them along the foraging trail or by standing their ground and fending them off with their legs, antennae, and mandibles. At the colony level, susceptible foragers are protected against parasitism by a shift in the forager size distribution toward smaller unsusceptible sizes during the day when parasitoids are active and toward larger sizes at night when parasitoids are inactive. The frequency of parasitism of susceptible foragers was 15%, which is more than five times the frequency found in another system involving the phorid parasitoid Apocephalus attophilus and the leaf-cutting ant host Atta colombica. We offer several possible explanations for such differences in the frequency of parasitism and also examine reasons for the high incidence of superparasitism (19%) observed in the system studied.