A study of sexual receptivity in Blabera craniifer Burm. (Blattaria)

Abstract

In females of the Blaberidae sexual receptivity is inhibited during the preoviposition period and during gestation. Similarly affected are oöcyte development and corpora allata activity during pregnancy. Roth (1964b) believes causation to be due to the mechanical action of the oötheca, but Engelmann (1964) believes it is due to the intervention of a humoral agent. In normal females of Blabera craniifer sexual receptivity is linked to the presence or absence of the oötheca in the brood sac. If the oötheca is not placed in the brood sac receptivity appears sooner than in a pregnant female. If certain afferent pathways are suppressed (by severing the nerve cord), or upset (by anaesthesia or in surgical controls) during pregnancy, only a partial receptivity is shown: straddling of the female on the male abdomen, ‘licking’ of tergal secretions, but no insertion by the male occurs. Such reactions are repeated over several days, giving an alternation of partial receptivity/non-receptivity which differs from that shown in normal animals. At times desynchronization between the receptivity and laying cycles is observed. This leads to the same conclusion as Roth and Barth (1964) that receptivity is not directly controlled by the corpora allata. We believe that the control ‘centre’ of receptivity has an autonomous rhythm, which is normally hidden but which appears when the afferent pathways are lacking or upset. The control mechanism of mating behaviour is probably a neuro-endocrine mechanism.