PREDATION ON THE HORN FLY (DIPTERA, MUSCIDAE) BY 5 SPECIES OF PHILONTHUS (COLEOPTERA, STAPHYLINIDAE)

The feeding rates of adults and larvae of 5 Philonthus species were co mpared in the laboratory by measuring their consumption of eggs and la rvae of the horn fly, Haematobia irritans (L.). When confined in petri dishes with abundant prey, adults and larvae of Philonthus longicorni s Stephens had a higher predation rate than did those of P. centralis (Gravenhorst), which in turn had a higher rate than did those of P. fl avolimbatus Erichson. When given a choice, adults and larvae of P. lon gicornis devoured more prey eggs than prey larvae, but P. ventralis de voured more larvae than eggs; adult P. flavolimbatus, P. sericans (Gra venhorst) and P. hepaticus Erichson devoured roughly equal numbers of prey eggs and larvae. The survival of 100 horn flies from egg to the a dult stage was compared in the laboratory using a substrate of cattle dung on soil in the presence of 1 adult Philonthus. Emergence of adult horn flies was reduced by 80.4, 54.8, 40.6, and 32.9% per beetle by P . longicornis, P. centralis, P. flavolimbatus, and P. hepaticus, respe ctively. Predation by P. longicornis increased as prey density increas ed. The relationship was similar to the type II functional response. T he 5 species of Philonthus are frequent inhabitants of cattle dung in northern Florida, and their adults presumably contribute to mortality of horn fly eggs and larvae in the field.