302 



THE INSECTS 



The horsefly (Haematobia irritans) rarely bites man. In these the palpi are much 

 longer than in Stomoxys, being as long as proboscis. These palps are also thick 

 and spatulate. 



Glossina palpalis. This is the tsetse fly that is responsible for the 

 transmission of human trypanosomiasis (sleeping sickness). 



The tsetse fly is a small brownish fly about 1/3 of an inch long. The pro- 

 boscis extends vertically and has a bulb at its base. The arista is plumose 

 only on the upper side and the individual hairs are themselves feathered. 

 The wings are carried flat, closed over one another like the blades of a pair of scissors 



FIG. 86. Insects in which the adult stage is important, (i) Stomoxys cal- 

 citrans; (2) S. calcitrans, larva; (3) Tabanus bovinus; (4) Tabanus larva; (5) Glossina 

 palpalis; (6) G. palpalis, side view; (7) G. palpalis pupa; (8) Glossina palps and arista. 



and project beyond the abdomen. The most characteristic feature of the tsetse 

 fly is the way the fourth longitudinal vein bends up abruptly to meet the mid cross 

 vein and then curves downward to run parallel with the third longitudinal vein. 

 In Stomoxys, the wings separate; in Haematopota they just meet, and in Glossina 

 they cross. Glossinae bite chiefly in the daytime. 



The tsetse fly does not lay eggs, but gives birth to a single full-grown larva 

 almost as large as the mother which immediately bores its way into the soil and 

 becomes a pupa. 



The pupal stage is about a month and the larval stage in the mother about two 

 weeks. G. palpalis bites in the day time. Both males and females bite. Glossina 



