Morphology and ultrastructure of an intertergal pheromone gland in the abdomen of the pine sawfly Neodiprion sertifer (Insecta, Hymenoptera): a potential source of sex pheromones

Abstract

An abdominal intertergal gland of the sawfly Neodiprion sertifer was found in both sexes of the sawfly N. sertifer, which is in contrast with Diprion similis, in which the gland is known only from the female. The gland lies laterally on each side of tergite II in the fat body between the tergite wall and trachea and opens into the fold of the arthrodial membrane between tergites II and III. The emission of secretion from the gland is controlled by a muscle opening the gland duct. Expansion of the lateral trachea probably forces the secretion out of the gland's lumen.The intertergal gland is a typical insect epidermal pheromone gland formed by three cell types: glandular, ductule, and hypodermal cells. The glandular cells have microvilli-lined cavities surrounded by numerous mitochondria. From these cavities arise ductules, surrounded by ductule cells, merging into other ductules that open into the lumen of the gland. The hypodermal cells underlie the cuticular walls of the lumen. This scheme is now well-known from many insect species as typical of epidermal pheromone glands with a draining duct. Finally, the possible function of the intertergal gland's secretion is discussed.