THE EFFECT OF PREY DENSITY ON THE PREDATORY ABILITY OF THREE SPECIES OF PHILONTHUS (COLEOPTERA: STAPHYLINIDAE) ASSOCIATED WITH CATTLE DUNG

CHANI POSSE, M. R.

Foz de Iguazú, Brasil

Congreso; XXI INTERNATIONAL CONGRESS OF ENTOMOLOGY (XXIICE); 2000

Sociedade Entomologica do Brasil - Embrapa

Insect predators inhabiting bovine dung pats may influence populations of dung breeding flies. Several species of predators have been reported attacking dung breeding Diptera in North America (Roth 1982; Summmerlin et al. 1982; Fincher 1994; Hu et al. 1996; Hu et al. 1997) and southern Africa (Fay 1980; Doube et al. 1987; Doube 1987) and they have long been viewed as potential biological control agents. The introduction of the horn fly Haematobia irritans irritans (Diptera: Muscidae), in southern Brazil, Paraguay, Uruguay and Argentina stimulated interest in research on the identification, biology, and utility of such species (Fletchmann 1995; Cabrera Walsh et al. 1997; Guimaraes et al. 1998; Lizarralde de Gosso et al. 1999). Predation by staphylinid beetles of the genus Philonthus has been implicated as a mortality factor of dung-breeding flies. Although the predation potential of Philonthus species appears well documented, there is only limited information published on the capacity of the southamerican fauna to prey upon the pre-adult stages of flies. Objectives of this study were to evaluate the functional responses of three Philonthus species frequently associated with cattle droppings in Tucuman, Argentina. Adult Philonthus spp. were collected from naturally deposited dung by collecting the excrement in the field, returning the manure to the lab and removing the insects by flotation. Rearing techniques was developed by following the method of Hunter et al. (1986) for Philonthus. For observation, individual beetles from egg to adult were confined under laboratory conditions and house fly (Diptera: Muscidae) eggs and 1st instar larvae were provided for food. The feeding rates of adults and larvae of Philonthus bruchi, P. flavolimbatus and P. pauxillus were compared at different densities of prey in the laboratory by measuring their consumption of available prey. The results of predation by these species, Philonthus bruchi (from Argentina, collected in Tucuman), P. flavolimbatus and P. pauxillus (Neotropical species, collected in Tucuman) on the immature stages of house flies are reported. When confined with abundant prey, adults and larvae of P. bruchi had a higher predation rate than did those of P. flavolimbatus, which in turn had a higher rate than did those of P. pauxillus. The relationship derived from functional responses in both larvae and adults of these species was similar to the type II functional response. Index terms: Philonthus bruchi, Philonthus flavolimbatus, Philonthus pauxillus, house fly, functional response