The ultrastructure of the pygidial defence glands of the carabid Pterostichus madidus F

Pygidial defence glands, which are universal in Caraboidea, are paired, cuticular invaginations of the body wall. In Pterostichus madidus F. the glands contain a nauseous, corrosive secretion that can be discharged forcibly to deter attack by predators. The cells producing the secretion are of one type only. Electronmicroscopy shows that the ducts which drain these cells are not intracellular but are separated from the cell contents by a plasma membrane. The cuticular walls of the duct appear to effectively screen the cell from the disruptive effect of its final products of secretion. The duct‐carrying epidermal cells which are modifications of the epidermis covering the rest of the gland support the ducts from the secretory vesicles to their entry into the central lumen of each secretory lobe. There is a single duct‐carrying cell around each duct.