STRUCTURE AND FUNCTION OF SEX PHEROMONE GLANDS OF MALE QUEENSLAND FRUIT FLY, DACUS TRYONI

Sexually mature male Dacus tryoni release a sweet-smelling substance during courtship. This is secreted and stored in a secretory sac and reservoir which are associated with the posterior region of the rectum. Both structures appear 5 days after pupation in the 2-day-old pharate adult and are initially lined with cuboidal epithelium. By the fourth day after pupal-adult apolysis the epithelium becomes glandular. In the immature fly both the reservoir and secretory sac are lined with glandular epithelium but, as the fly matures, the secretory epithelium in the anterior region of the reservoir is replaced by squamous epithelium. Pheromone was first detected in flies 2 days after emergence, but in the majority the reservoir does not become full of secretion until 12 to 14 days after emergence. There is a close correlation between the amount of secretion in the reservoir and the onset of sexual activity. Sexually receptive females responded to extracts of the reservoir by characteristic types of behaviour including preening and probing with the ovipositor. The probing response was used as a bioassay to test the response of females of different ages to extracts of the reservoir and also their response at different times of day. Females responded maximally when their ovaries were mature, and around the dusk period, which is the normal time of mating in this species. © 1969.