Cells of the thoracic defensive gland of the red-humped caterpillar, Schizura concinna (J. E. Smith) (Lepidoptera: Notodontidae): ultrastructural observations

Abstract

The thoracic defensive gland in larvae of Schizura concinna J. E. Smith consists of an anterior and posterior gland joined by an interglandular neck. Ultrastructural observations indicated that there are no cuticular ductules associated with gland cells and that there are three, or possibly four, types of cells within the gland. Two types, as suggested by their location, probably function to maintain the form of the orifice and the interglandular neck. The remaining cells, located in the anterior gland, the anterior lateral longitudinal folds, and the posterior gland exhibit no appreciable ultrastructural differences from each other. Only the cells of the lateral longitudinal folds contain deposits of a lipid-like material. The apical plasma membranes of these cells have a peculiar array of folds surrounding cylinders of endocuticle. Within the apical folds these cylinders are encircled longitudinally by tubules which presumably arise from smooth tubular endoplasmic reticulum. Within the cuticle overlying the cells are filaments which are similar in appearance to the secretion contained within the lumen of the glands.