Protein Feeding and Oviposition Effects on Attraction of Screwworm Flies (Diptera: Calliphoridae) to Host Fluids

Abstract

Olfactometers were used to study effects of protein feeding and oviposition on attraction of adults of the screwworm, Cochliomyia hominivorax (Coquerel), to host blood and wound fluids. Engorgement accompanied oviposition on a proteinaceous substrate, and about 80% of the feeding that occurred in association with oviposition was observed after egg laying began. Oviposition with feeding reduced attraction; oviposition alone did not. Protein feeding 60-90 min before bioassay reduced responsiveness of vitellogenic nullipars but not gravid ones; however, a transient drop was detected 30 min after gravid flies fed. This pattern correlated with the reluctance of gravid females, unlike vitellogenic ones or those that oviposited, to engorge fully. The results confirmed existence of a feeding attractant and supported the hypothesis that a feeding attractant associated with hosts draws females with immature ovaries and those seeking oviposition sites.