Notes on certain aspects of the development of trypanosoma gambiense in glossina palpalis

In the course of an attempt to obtain an insight into the details of the life-cycle of Trypanosoma gambiense in Glossina palpalis, certain experiments were undertaken involving the feeding of a relatively large number of flies under closely observed conditions. Although primarily undertaken with a view to the morphology and development of the parasite, they have a bearing on the general relation between the trypanosomes and the Glossina that is of some interest. The present account deals with the infections produced in the flies as a whole; the morphological results will be considered in detail elsewhere. I must point out that the experiments in question are not concerned with actual transmissions of T. gambiense from an infected to a clean host, but with the number of flies in which the trypanosomes will develop. That flies harbouring trypanosomes are infective from about the 26th day onwards has been shown over and over again; it was therefore considered to be a wanton waste of life to allow every cage kept beyond the 30th day to infect a clean animal. Late cages were usually fed on cock’s blood after the 24th day. A small proportion were actually tested and an infection was invariably produced if the box contained flies showing trypanosomes.