The effect of fly age, sex, and period of starvation on the uptake and development of Trypanosoma congolense infection was examined in Glossina morsitans morsitans. In a study consisting of 1739 specimens of various ages, young unfed 16-hr-old flies and 2-day-old starved flies developed significantly higher mature infections than 2-day-old and 7-day-old flies which had been fed previously on a clean blood meal. Females displayed significantly higher immature infections, while mature infections were recorded more frequently in males, suggesting that females possess a stronger barrier to trypanosome development. The possible factors involved are discussed.
