Seijiro Morohoshi

Effect of the brain on the suboesophageal ganglion and determination of voltinism in Bombyx mori

Abstract It is known that voltinism in the silkworm is affected by inhibitory and promoting functions of the brain through the nerve commissures on the suboesophageal ganglion or the corpora allata. It was demonstrated that the brain has only an accelerative function through the nerve commissures on the secretion of the suboesophageal ganglion and has no inhibitory function. Voltinism in the silkworm is determined by the amount of the suboesophageal ganglion hormone. When silkworms have a large quantity of this hormone, they lay diapause egg batches, and when they have a small quantity, they lay non-diapause egg batches. The quantity of its hormone is modified by two factors; one is the brain-suboesophageal ganglion system (diapause direction) and the other is the brain-corpora allata system (non-diapause direction).

Hormonal studies on the diapause and non-diapause eggs of the silkworm, Bombyx mori L.

Abstract It is known that the brain-suboesophageal ganglion complex in the silkworm converts the non-diapause egg into the diapause egg. It has been found that the corpus allatum is concerned not only with the number of moults but also with the production of non-diapause eggs. The influence of the suboesophageal ganglion differs with each voltine race, and it gradually becomes stronger with age, whereas the influence of the corpus allatum differs with each moulting race and becomes weaker with age. The brain does not perfectly control the secretion of both the suboesophageal ganglion and the corpora allata, but weakly inhibits and also weakly promotes their secretory activity. The corpus allatum and suboesophageal ganglion hormones consist not only of non-diapause and diapause hormones, but also of growth-promoting and inhibitory hormones.