Reproductive Factors Affecting Responses of the Screwworm Fly, Cochliomyia hominivorax (Diptera: Calliphoridae), to an Attractant of Bacterial Origin

Abstract

Attraction of screwworm flies, Cochliomyia hominivorax (Coquerel), to steam distillate of culture medium inoculated with the bacterium, Providencia rettgeri (Hadley, Elkins, and Caldwell), was studied in laboratory olfactometer assays conducted with 0- to 12-d-old males and nulliparous females. Males, and females with previtellogenic ovaries, were not attracted. Those with vitellogenic ovaries demonstrated only a trace response. Females became gravid as early as 4-5 d, but the percentage of gravid females attracted increased linearly with age up to 10 d. Insemination significantly enhanced responsiveness without affecting the rate of ovarian development. Gravid mated females 10-12 d old were the most strongly attracted. The results were consistent with the hypothesis that bacterial metabolites contribute to the attractiveness of wounds on screwworm host animals.