26 



INSECTS AND HUMAN WELFARE 



more remote. As is well known, sleeping sickness depends 

 for its spread entirely upon certain biting flies known as 



Fig. 11. T.set.se-flies. Above, 67ox«i«a pa/pah's, the carrier of human sleeping sick- 

 ness; below another species of Glossina with a more enlarged view of the head and 

 blood-sucking mouth parts. 



tsetse-flies belonging to the same family as our common house- 

 fly and stable-fly. The genus Glossina (Fig. 11) in which 



