Parturition in the tsetse fly Glossina morsitans: Pattern of activity,sound production and evidence for control by the mother's brain

The mature tsetse larva descends slightly in the uterus causing a protrusion of the female's abdomen and a thrusting open of the female vulva 5–6 h before parturition. Coinciding with larval descent, the female becomes conspicuously restless. The activity pattern monitored by measuring oxygen consumption shows a progression of four discrete stages of activity before and after parturition. Immediately following parturition, the female emits a low frequency sound of 5.8 min duration that differs markedly from sounds produced during feeding or mating. Parturition can be blocked by neck-ligation of the female, thus suggesting a crucial role for the brain. Both neural and hormonal pathways appear to be involved. Transection of the nerve that innervates the uterine muscles reduces the incidence of successful parturition, and parturition in neck-ligated females can be stimulated by transfusion of haemolymph from females that have recently given birth. When parturition is blocked, larvae are retained in utero but eventually pupariate after a delay of 2.3 days.