Studies on the neurosecretory system of Iphita limbata stal. Part V. Probable endocrine basis of oviposition in the female insect

Abstract

On the basis of histological and experimental studies involving blood transfusions, injection of ovarian extracts, and transplantation of neurosecretory cells, it is concluded that there is an endocrine basis for oviposition in the insect Iphita limbata Stal. (Pyrrhocoridae: Hemiptera), a common plant bug of South India. Oviposition is brought about in the gravid female by a hormone-complex involving the interaction between the ovary and the neurosecretory system. It is tentatively postulated that it probably works out as follows: Stainable neurosecretory matter from the cells of the pars intercerebralis of the brain passes along the axons of the allatic nerve to the corpus allatum. This stimulates the gland which consequently begins to enlarge and initiates egg-growth by deposition of yolk. When eggs become full grown and ripe,i.e., when the animal becomes gravid, the ovarian wall releases a substance into the blood which may be presumed to exert a dual action on the neurosecretory system. Evidences show that the supply of visible, stainable, neurosecretory colloids to the corpus allatum is reduced or inhibited, which may result in an inactivation of the gland and stops further elaboration of yolk in the eggs. At the same time, the blood-borne factor influences the cells of the pars intercerebralis to release their colloids into blood. This release of neurosecretory matter may have a role in inducing oviposition by promoting oviducal contractions.