Because of their haematophagous and viviparous habits, female Glossina austeni undergo large changes in both volume and weight during each pregnancy cycle. As the developing larva in the uterus increases in size, the volume of the mother also increases. These changes in volume of the adult fly occur almost exclusively in the abdomen, which does not contain significant air sacs with which to buffer the volume changes. The changes in abdominal volume are made possible by an elastic ventral abdominal cuticle which is manifested in histological sections as changes in the thickness of the ventral abdominal cuticle during the pregnancy cycle. Stretching appears to occur in the endocuticle.Female G. austeni tend to feed to a constant weight irrespective of their reproductive state. Before the first ovulation, flies feed to a weight of about 50 mg but subsequently feed to a weight of about 80 mg. This increase coincides with the cessation of postemergence cuticle deposition, as well as ovulation, but it is not known whether these events are functionally related.Haemolymph volume of female G. austeni remains at a low level throughout the observed pregnancy cycles at a value of about 5 μliters. This small volume may impose limitations on the transport of nutrients through the haemolymph. Following feeding, haemolymph volume does not change.