An Agar/Parafilm membrane system, developed for feeding tsetse flies, was evaluated by comparing membrane-fed and goat-fed female Glossina morsitans morsitans Westw. with respect to the following: fly weight, meal size, trypsin levels and amount of protein in the posterior midgut, and the portion of midgut protein which is in the posterior midgut. In flies having the same prefeeding history, the digestive physiology of membrane-fed flies was not significantly different from those fed on goats. The offspring of membrane-fed flies were lighter, took smaller meals, and had less trypsin and protein in the posterior section of the midgut than did flies from the stock animal-fed colony. However the relationship between trypsin levels and protein in the posterior part of the midgut was the same in flies from animal-fed and membrane-fed colonies.