The Diapause Hormone of the Silkworm, Bombyx mori

Abstract

IN 1924, Watanabe1 postulated that silkworm eggs overwinter as a result of receiving an ‘inhibitory’ substance from the mother moths, but the existence of the substance has not hitherto been substantiated experimentally. On the other hand, I have found² that the subœsophageal ganglion of the silkworm is responsible for the hibernation of silkworm eggs; but the organ that furnishes the active principle was not known. Evidently diapause of the silkworm is controlled by a hormone, similarly to the moulting or metamorphosis of insects. I attributed³ the diapause of silkworm eggs solely to the function of the subœsophageal ganglion, the brain having no effect, whereas Fukuda⁴ ascribed the activity of the subœsophageal ganglion to brain regulation by way of the œsophageal connectives. Thus in both hypotheses the subœsophageal ganglion is regarded as the actual source of the principle leading to the production of diapause eggs. It was not known whether the substance secreted from the subœsophageal ganglion—the diapause hormone—is identical with the inhibitory substance suggested by Watanabe or not.