Sperm Penetration of Housefly Eggs: Evidence for Involvement of a Female Accessory Secretion

Abstract
Removal of the paired sex accessory glands associated with the posterior reproductive tract of female houseflies inhibited penetration of the eggs by sperm, but the insemination of females without these glands appeared to be unaffected. The results indicate that either the sperm are "activated" or the permeability of the egg membrane is altered by the secretion of the accessory glands before fertilization occurs.