DEVELOPMENT-ACTIVITY RELATIONSHIPS IN NYMPHAL CORPORA ALLATA OF THE COCKROACH, DIPLOPTERA-PUNCTATA

In females of Diploptera punctata the corpora allata undergo a gradual increase in volume during most of the second nymphal stadium. In the first half of the stadium, steady growth of the glands results from a progressive increase in the size of constituent cells. Late in the sta dium, cell size declines but the volume of the glands continues to ris e due to an increase in cell number Changes in cell size during the st adium displayed a distinct pattern in relation to Juvenile Hormone (JH ) synthesis. Both cell size and activity increased during the first tw o-thirds of the stadium, peaked early in the last third of the stadium , and decreased before the moult. The rise in cell numbers fate in the stadium corresponded to a wave of cellular mitosis and occurred after a steep decline in the rate of JH biosynthesis. Exposure of late seco nd instars to fenoxycarb, a JH analogue, depressed mitosis significant ly, suggesting autocrine regulation of cell proliferation in on the co rpora allata. Possible mechanisms modulating sequential cycles of grow th and atrophy of cells and cell proliferation in these glands are dis cussed in relation to temporal patterns of JH and ecdysteroid titres i n nymphs.