Quarterly Journal of Microscopical Science, Vol s3-103, 359-367, Copyright © 1962 by Company of Biologists

Breakdown and Formation of Connective Tissue in the Pupal Stage of an Insect

¹ Northwestern University, Evanston, Illinois

Changes occurring in the connective-tissue elements in the pupae of some Diptera Cyclorrhapha are described. The larva and the adult are characterized by an organically continuous system of investing membranes. The pupa is, on the whole, characterized by the absence of investing membranes. Early in the pupa most of the larval membranes are destroyed. In some cases the associated cells also disappear; in others the cells remain. Disappearance is not simultaneous throughout an organ; usually the anteriormost segments of the organ disappear first. The adult membranes are formed in the late pupa, after the processes of growth, cell-division, and differentiation are completed. Fusion of membranes would appear to result from co-ordinated secretion, and be a delicately timed process. It is suggested that the larval membranes are similarly produced in the embryo, at the end of differentiation and organ formation, and that in the case of both larva and adult, the invested cells are concerned with the secretion of, and the destruction of, the investing membranes.