ABSTRACT
In the blood-sucking bug Rhodnius prolixus there are five nymphal stages, throughout which the morphological characters remain comparatively constant. At the fifth moult, when the insect becomes adult, there are striking changes in all parts of the body. It is convenient to refer to the appearance of these adult characters as ‘metamorphosis’—though without suggesting that this change is exactly homologous with meta-morphosis in endopterygote insects. Thus in the growth of Rhodnius there are two distinct phenomena to be considered : simple moulting, and moulting coupled with metamorphosis. In a previous paper (Wigglesworth, 1933) the histological changes in the epidermis during moulting and metamorphosis have been described ; in the present paper an attempt will be made to analyse some of the factors which regulate these processes.
