Cockroach molting. I. Temporal organization of events during molting cycle of Blattella germanica (L.).

The molting cycle of insects has long been used as a model system for studying development. Studies on hormonal control mechanisms (Wyatt, 1972; Doane, 1973; Willis, 1974), pattern formation (Locke, 1967; Lawrence, 1973) and neuronal development (Edwards, 1969) have effectively used the molting and metamorphic cycles of insects to add to our understanding of development. Two insect species which have contributed greatly to this understanding are the blood-sucking bug, Rhodnius prolixus (Wigglesworth, 1934), and the Cecropia silkmoth, Hyalophora cecropia (Williams, 1946). One reason both of these insects are particularly suited for studies of development is that their development can be controlled by extrinsic environmental cues (Edwards, 1966) allowing them to be manipulated by an experimenter. This paper introduces an approach to the study of cockroach development using feeding (Kunkel, 1966) and regeneration (O'Farrell and Stock, 1953) as extrinsically controllable cues for regulating the development of cockroach cultures. These cultures are used as sources of animals of specified developmental age for experimentation (Kunkel, 1973, 1975; Kunkel and Lawler, 1974). In particular this paper describes a structuring of the molting cycle of Blattella germanica into two functionally and experimentally separable phases, the intermolt phase and the molt phase. I also describe some simple assays for landmark events during the molting cycle and establish some limits of usefulness for the synchronous cultures.