The presence in salivary secretions of Glossina morsitans of stages of Trypanosoma (Trypanozoon) brucei other than those occurring in the salivary glands.

Using the bat wing membrane technique to study salivary secretions of Glossina morsitans infected with Trypanosoma (Trypanozoon) brucei, it was shown that flies extrude infected salivary secretions as early as day six after an infective blood meal. The non-salivary-gland stages of T. (T.) brucei were extruded intermittently and flies infected with such trypanosomes were not all destined to develop metacyclic infections. Once the salivary glands were involved, the trypanosomes appeared in the secretions each time the flies were tested. Some of the flies with gut infections, but no demonstrable salivary gland involvement, transmitted T. brucei to mice and it is suggested that these infections were intiated by some of the proventricular trypanosomes secreted with saliva.