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 Neodohmiphora curvinervis and the antiparasitoid defense behavior of i ts leaf-cutting ant host Atta cephalotes. N. curvinervis females are d iurnal 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 host s is usually initiated when an outbound forager of acceptable size pas ses by a parasitoid perch site. Individual foragers defend themselves against pursuing parasitoids by outrunning them along the foraging tra il or by standing their ground and fending them off with their legs, a ntennae, and mandibles. At the colony level, susceptible foragers are protected against parasitism by a shift in the forager size distributi on toward smaller unsusceptible sizes during the day when parasitoids are active and toward larger sizes at night when parasitoids are inact ive. The frequency of parasitism of susceptible foragers was 15%, whic h is more than five times the frequency found in another system involv ing the phorid parasitoid Apocephalus attophilus and the leaf-cutting ant host Atta colombica. We offer several possible explanations for su ch differences in the frequency of parasitism and also examine reasons for the high incidence of superparasitism (19%) observed in the syste m studied.