Evidence of hormonal control of ovulation in tsetse flies.

ODHIAMBO1 and Saunders and Dodd2 reported that the first fully developed egg in the tsetse fly (Glossina pallidipes1 and G. morsitans2) is not released from the ovary into the uterus until the female has had mating experience. They observed that the component of the mating act causing ovulation was not insemination, and suggested that a mechanical factor is responsible for the initiation of ovulation2. It is difficult to see how a strictly nervous mechanism could account for the time lag between mating and ovulation (females mated 2–3 d after emergence usually ovulate 6–7 d later). Foster3 found that the ablation of median neurosecretory cells (MNC) of the pars intercerebralis almost always inhibited ovulation in G. austeni. He noted, however, that surgical brain trauma also inhibited ovulation in control flies. Ejezie and Davey4 found that the MNC undergo cyclic changes of net synthesis and release in G. austeni and attempted to correlate these phenomena with ovulation and larviposition. We describe here investigations of the control mechanism of ovulation in G. morsitans morsitans.