TEE FLY AND ITS ALLIES 65 



A member of the family Muscidse, which is especially 

 destructive in tropical Africa, is the tsetse-fly (Fig. 63). 

 The bite of this fly is so dangerous that horses and dogs 

 cannot penetrate the region infested by it. Even herds of 

 cattle may be killed by this fly. Consequently travellers 

 have been hindered in penetrating into this country, and 

 the opening up of tropical Africa to agriculture and com- 

 merce has been much interfered with. The injurious 



FIG. 63. Glossina moristans, the tsetse-fly. FIG. G4. Syrphus. From 

 From the " Standard Natural History." Packard. 



effect of the bite of this fly is due to a parasite introduced 

 by it into the body of the victim. 



Another destructive family includes the bot-flies ((Estii- 

 dse 1 ), which have a general resemblance to honey-bees or 

 bumblebees. Their larvae are parasitic in mammals. Of 

 this family the bot-fly of the horse, Grastrophilus 2 equif is 

 the most generally known. These flies hover about the 

 legs of horses and lay their eggs upon the horse's hair. 

 The larvaa, irritating the horse's skin, are licked by the 

 horse into its mouth and swallowed. In the stomach or 



, gadfly. 2 yourr-ftp, belly ; 0i\k>, to like. 3 Of the horse. 



