Intra- and interspecific sex pheromone responses of screwworm and secondary screwworm flies

A laboratory behavioral assay examined intra- and interspecific responses to sex pheromone by screwworms,Cochliomyia hominivorax, and secondary screwworms,C. macellaria, in relation to the duration of colonization ofC. hominivorax test males. Females ofC. macellaria, like those ofC. hominivorax, were found to produce a pheromone that stimulates male copulatory attempts on contact. Newly colonized (<22 generations)C. hominivorax males did not respond toC. macellaria pheromone, indicating that pheromone contributes to reproductive isolation between these two closely related species. Although long-colonized (>200 generations)C. hominivorax males did respond toC. macellaria females or their extract, this behavior was infrequent and significantly less common than intraspecific responses. DeprivingC. macellaria adults of dietary protein did not affect the potency of female extracts, but did reduce male responsiveness to pheromone. These results provided little evidence that colonization reduces the ability ofC. hominivorax males to differentiate betweenC. hominivorax andC. macellaria females using sex pheromones.