THE FLIES 



47 



solution of the problem probably lies in immunization against the 

 tsetse fly diseases, as to which little progress has yet been made. 



Family V. Hippoboscid^ 



Diptera (p. 23). — The body is flattened. Wings are present or absent. 

 The wing veins are crowded toward the anterior margin. The head is 

 sunk into an emargination of the thorax; the antennae inserted in pits 

 near mouth; mouth parts adapted for piercing and sucking blood. 

 The legs are stout, terminated by strong claws. The abdomen is large 

 and sacular with segments indistinct. 



The Hippoboscidse are pupiparous, the eggs being hatched and 

 nearly the whole of the larval stage passed within the body of the parent. 

 The larvae are extruded only when nearly ready to transform into pupae. 



All are parasitic upon birds and mammals. . Hippobosca equina is a 

 winged species occurring upon the horse, and known in England as the 

 forest fly. 



Melophagus Ovinus 



The sheep "tick." — Hippoboscidae (p. 47). Three-sixteenths to one- 

 quarter of an inch in length. The color reddish or grayish brown. 

 The wings and halteres are ab- 

 sent. The head is small and 

 sunken into the thorax; ab- 

 domen large, sac-like, and 

 covered with short spines 

 (Fig. 25). 



Life History. — Matured lar- 

 vae are extruded from the body 

 of the female and at once enter 

 upon their pupation, the red- 

 dish brown pupae adhering to 

 the wool fibers. The pupal 

 stage occupies three to six 

 weeks according to season and 

 temperature, the shorter period 

 occurring during the summer. 

 At sexual maturity the deposi- 

 tion of pupae begins, each fe- 

 male depositing from eight to 

 ten. Probably the life of the 

 tick will not exceed four to five 

 months. 



Occurrence. — The sheep tick is distributed over all parts of the 

 world where sheep are kept. Its parasitism is continuous, the pupiparous 



Fig. 25. — Melophagus ovinus (from photo- 

 graph of mounted specimen, by Hoedt). 



