Endocrine Activity During Insect Embryogenesis. Function of the Ventral Head Glands in Locust Embryos (Locustana Pardalina and Locusta Migratoria, Orthoptera)

Abstract

1. A brain-ventral head gland system operates in embryos of Locustana pardalina and Locusta migratoria. 2. The initiation of growth and differentiation on the termination of diapause in the egg of pardalina takes place before the ventral head glands are formed. 3. Maximal activity in the ventral head glands coincides with the retraction of the epidermis from the cuticle. 4. Embryos, dissected out of the egg, were kept alive in aerated sterile Ringer's solution for up to 2 weeks during which time they progressed in their development. 5. If post-katatrepsis embryos are ligatured between the thorax and abdomen before a ‘critical’ period the moult is limited to the thorax. If ligatured immediately behind the head, the body fails to moult. 6. Since on the termination of diapause in the egg of pardalina mitosis begins before the formation of the ventral head glands, it is suggested that in locust embryos these glands are exclusively concerned with the retraction of the epidermis from the cuticle. 7. It is suggested that the uptake of water by the egg of pardalina in stretching the cells stimulates a growth factor which, although present throughout the diapause phase, is only capable of initiating mitosis after the diapause phase has come to an end.