Sexual and Temporal Differences in Phorid Parasitism of Photinus marginellus Fireflies (Coleoptera: Lampyridae)

Abstract

Photinus marginellus LeConte fireflies maintain discrete breeding aggregations in which males fly and flash in search of conspecific females, while females respond from perches in vegetation. Sexual differences and temporal patterns in parasitism by the phorid Apocephalus antennatus Malloch, a specialist parasitoid of lampyrid beetles, were investigated by determining parasitism rates during the flight season within a P. marginellus deme. Female P. marginellus were attacked by parasitoids at slightly higher rates (35% of all females) than were males (25%), and females hosted significantly more parasitoid larvae per individual than did males. A distinct temporal pattern in parasitism rate was observed; for both male and female hosts, the probability of an individual being killed by A. antennatus increased markedly from early- to mid-season. Within each sex, there were no differences in host body size between parasitized and nonparasitized beetles, and no relationship was found between host body size and the number of phorid larvae that emerged. Intersexual differences and temporal patterns of parasitism observed in this study suggest that A. antennatus may affect P. marginellus life histories and reproductive ecology.