Mating behavior of the screw-worm fly as affected by differences in strain and size.

Abstract

The effects of differences in strains and size on the mating frequency of male screw-worm flies, Cochliomyia hominivorax (Coquerel), were studied in observed mating tests with a recently colonized (Mexican) and a laboratory-adapted (Florida) strain of flies. Large or small males of the Florida strain were obtained by rearing the flies on 2 different artificial media. Flies comparable in size to wild flies were reared in artificial wounds on sheep. Ancillary studies required sterilization of the males by exposure to gamma irradiation. Differences in mating frequency among male flies that were attributable to strain disappeared after the Mexican flies had been colonized for 15 generations. However, differences in mating frequency between large and small Florida males persisted, regardless of the strain of the female flies, when the females were as large as flies in natural populations.