Hormonal control of the malpighian tubules of the stick insect, Carausius morosus.

Factors have been isolated from the central nervous system of the stick insect, Carausius morosus, which affect the rate of secretion of the Malpighian tubules (Gersch et al. i960; Unger, 1965; Vietinghoff, 1967), but it has not yet been shown that these factors are of physiological importance in vivo. There is, however, an accumulation of stainable material in the corpora cardiaca of Carausius on dehydration (Pflugfelder, 1937), and Ramsay (1955a) found that the rate of secretion of tubules in situ varied according to the state of hydration of the insect. The control of the Malpighian tubules by a hormone originating in the nervous system, whose level in the haemolymph has been shown to vary, has been demonstrated in Rhodnius (Maddrell, 1963), Dysdercus (Berridge, 1966a) and Periplaneta (Wall & Ralph, 1964; Mills, 1967; Mills & Nielsen, 1967), and similar control is suspected in a number of other species. This paper reports the occurrence in Carausius of a diuretic hormone and examines its significance in the regulation of water balance.