Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2003
Publication Date: 5/1/2003
Citation: Petersson, E., Sivinski, J.M. 2003. MATING STATUS AND CHOICE OF GROUP SIZE IN THE PHORETIC FLY NORRBOMIA FRIGIPENNIS (SPULER) (DIPTERA: SPHAEROCERIDAE). Journal of Insect Behavior. 16(3):411-423. Interpretive Summary: Understanding the mating systems of insects can be important in their control. For example, both sterile male and pheromone controls require knowledge of where insects are likely to mate, how the sexes approach each other and what communications occur between males and females. General theories of the evolution of insect reproduction allow entomologists to predict the behaviors of pests and direct their research in the most appropriate direction. These general theories are often honed by examinations of species that exhibit highly specialized behaviors. Norbommia frigipennis, a small fly that mates on the backs of dung beetles, is such a species. Scientist from Uppsala University, Sweden, and the Center for Medical, Agricultural and Veterinary Entomology, U. S. Department of Agriculture, Gainesville, FL conducted experiments in the field and laboratory that showed that female insects are capable of estimating the likelihood of obtaining high quality mates and avoiding competition from other females by "counting" the numbers of conspecifics. This capacity to estimate reproductive opportunities at the sites of particular resources has sometimes been assumed to occur in insects but has not been previously demonstrated. Future studies of specialized insects may further define the limits of their behavioral flexibility.
Technical Abstract: The fly Norrbomia frigipennis (Sphaeroceridae) is a phoretic kleptoparasite. The insects mate on scarab dung beetles, follow them underground and lay their eggs in the feces collected by the beetles. Numbers of flies on the beetles varies from one to ca. twenty. In the field larger and smaller groups contain greater than expected numbers of females. Virgin females and females with unmatured eggs were most frequently found in large groups. Laboratory experiments by scientists at the Center for Medical, Agricultural and Veterinary Entomology an the Department of Animal Ecology, Uppsala University, Sweden, revealed that mated females avoided larger groups. These results suggest that N. frigipennis can "count" conspecifics, and choose groups either likely to have the greatest numbers of potential mates or the fewest competitors for oviposition resources.