The Eltringham organ and a new thoracic gland: Ultrastructure and presumed pheromone function (Insecta. Myrmeleontidae)

Eltringham's organ is a club-like projection from the posterior margin of hind-wings of some myrmeleontid insects. It bears laterally directed setae, each having a specialized epidermal cell beneath, which gives off secretion into a sub-setal lumen. The lumen continues into the wall of the moat-like socket of the setae. Eltringham's organ fits into an excavation of the lateral body wall connected with the opening of a thoracic gland. The thoracic gland in these animals has not previously been described. It consists of a hollow tube, feebly developed in females. The tube wall houses two cell types: gland cells and cuticular cells. The latter form the cuticle of the general duct lumen and a specialized duct leading from each gland cell. The gland cells have a microvilli-filled cavity which collects the secretion. The thoracic gland produces a pheromone secretion whose distribution is aided by Eltringham's organ where present