Three species of the genus Entomophthora were studied ultrastructurally with respect to primary spore formation and discharge: Entomophthora muscae (C) Fres., E. planchoniana Cornu, and E. culicis (Braun) Fres. The wall covering both the primary spore and the sporophore consists of two layers: an electron dense outer layer and a translucent inner layer. During spore development, a septum is formed between the spore and the sporophore. At the apex of the spore, the wall layers are diffuse and vesicles are present, and at the base, the outer layer is absent. After discharge, when a primary spore is attached to a substrate, the outer wall is separated into several layers. The outermost layers expands to cover a greater area than the spore itself. The mucus between the wall layers takes part in the adhesion of the spore to the substrate.