Each posterior spiracle is generally divided into three main parts—posterior spiracular plate, fell and spiracular chambers. The characteristic features of these parts and the moulting processes during the development of the larvae are described in the text. The main features in the development of the third instar larva are the replacement of the epidermal cells by chitin, shortening of the felt chamber and sear cord, increase in the depth of the spiracular chamber, gradual melanization of the posterior spiracle, and then its separation from the dorsal longitudinal trunk prior to pupation.