XV.—Observations on the Life Cycle and Immature Stages of Culicoides circumscriptus Kieff. (Diptera, Ceratopogonidæ).

Abstract

SynopsisThe immature stages of C. circumscriptus Kieff. are found in the mud of most Scottish salt marshes. The life cycle has been studied by means of laboratory cultures and by observation and periodic sampling at a salt marsh near Dumbarton. Data are given concerning the life cycle in the laboratory and out of doors. In the field there are two generations a year.In captivity the female lays a single large batch of eggs which adhere to the substrate by means of structures on the chorion. The eggs and the manner of oviposition and hatching are described. Descriptions of the larvae, supplementing those of previous authors are given. The first instar differs from older larvae in possessing a retractable prothoracic proleg, and is more sluggish in its movements, probably remaining near the oviposition site until the first ecdysis. Before pupation the larva comes to the surface. This is necessary for successful pupation, enabling the pupa to breathe and to form the buoyancy space. The pupa buries itself in the mud emerging only under flooded conditions to float on the surface or prior to ecdysis.