A study of the hatching process in aquatic invertebrates. XXV. Hatching in the blackfly, Simulium (probably venustum) (Diptera, Simuliidae)

Abstract

Hatching from the egg was studied in Simulium (probably venustum). In early stages of development the embryo completely fills the space enclosed by the chorion, but in later stages there are sizable fluid-filled spaces between the prolarva and the shell. Initiation of hatching involves the beginning of swallowing and absorption of the intrachorionic fluid. As a result of this the prolarva swells until it not only completely fills the egg again, but also exerts considerable pressure from within against the shell. This process brings the cephalic egg burster into strong contact with the chorion. Eventually the burster penetrates the shell and thus initiates the rupture which permits the first instar larva to escape from the egg, always head first.