ABSTRACT
The postembryonic growth of the compound eye of the cockroach Periplaneta americana involves increases in the size of the individual ommatidia as well as a 35-fold increase in the number of ommatidia. These ommatidia are added to the anterior, dorsal, and ventral margins of the eye by means of an almost continuous process of cell division in the proliferation zone in these margins. This proliferation phase is followed by a process of maturation of bundles of ‘pre-ommatidial’ cells into mature ommatidia, a process which involves further cell division. Processes involved in compound-eye development are investigated by eye margin grafting, histological techniques and cell proliferation studies.
Several studies (Klein, 1933; Nigam, 1933; Gould & Deay, 1938; Gier, 1947; Willis, Riser & Roth, 1958; Biellmann, 1960) have demonstrated the variability of the intermoult period. In the present and in other work conducted concurrently (Bray, 1978), some individuals within a group of cockroaches moult much later than the majority. There is no known way of precise staging in P. americana. The range of variability in the levels of cell division shown on particular days of the moult cycle may in part be due to differing rates of development of the animals examined at these stages.
