A gonadotropic inhibition is observed by means of oothecal production in Periplaneta americana after unilateral amputation of the mandible, the maxillary palp and the labial palp, in females reared with males at emergence. It is apparent that the sense organs of the mouthparts are involved in neuroendocrine regulatory mechanisms. In males, histological changes take place in the corpora allata. The findings support the implicit assumption that the secretory activities of the corpora allata are controlled by nervous impulses coming from the mouthparts, along neuroendocrine pathways.