THE INSECT WORLD. 



369 



A louse-fly, Olfersia species. 



be aired until no trace of odor remains before fires are again 

 introduced. 



The last family in the Diptera to which we need call attention 

 are the "louse-flies," or Hippoboscidcs, frequently separated as 

 a sub-order under the term Pupipara, the latter being applied 

 because of the curious method of reproduction. The flies are 

 parasites, living largely upon birds, but sometimes upon animals, 

 and the egg not only 



develops within the Fig. 424. 



body of the female, but 

 the larva becomes nearly 

 full-grown in the same 

 position, and practically 

 attains the pupa state 

 before it is extruded. 

 In these species the ab- 

 domen is somew^hat flat- 

 tened and oval in form, 

 of a thick, leathery con- 

 sistency, with a very 



large anal opening, and from the circumstances of the case only 

 one larva at a time is produced, so that the flies produce young 

 only at considerable intervals. The whole body is depressed or 

 flattened, and birds of prey are most usually affected. It is rare 

 to find a hawk, eagle, or owl upon which several specimens of 

 these peculiar flies cannot be found. They 

 move about rapidly, and their first impulse is 

 always to seek shelter when driven from their 

 original host. Thus, in handling hawks that 

 have just been shot, the flies frequently dart 

 upon the hunter and make their way under his 

 clothing and to his body. 



A few species are wingless, and among them 

 is the so-called "sheep-tick," Melophagus 

 ovinus, which is usually looked upon as a 

 louse, and resembles one in the prominent 

 proboscis, the lack of wings, and the strongly developed legs, 

 on which the claws are very prominent. This "sheep-tick" is 

 the only troublesome species, and it can best be kept in check 



24 



Fig. 425. 



Sheep-tick, Melopha- 

 gus ovinus. 



