The fine structure of developing type 'B' dermal glands in Rhodnius prolixus

The fine structure of the developing type 'B' dermal gland, the more common type in fifth instar larvae of Rhodnius, is described. Each gland consists of three cells responsible for secretion of the duct, saccule and secretion product or precursors, and a fourth capsule cell. The cuticular linings of the duct and saccule are secreted and shed synchronously with the cuticle of the body surface. Mechanisms of secretion and discharge are suggested.