264 NATURAL HISTORY 



annoyed with dipterous insects, which infest 

 every species, and are so large, in propor- 

 tion to themselves, that they must be ex- 

 tremely irksome and injurious to them. 

 These are the hippohoscce hirundines, with 

 narrow subulated wings, abounding in 

 every nest ; and are hatched by the warmth 

 of the bird's own body during incubation, 

 and crawl about under its feathers. 



A species of them is familiar to horsemen 

 in the south of England under the name of 

 forest'fiy ; and to some of side-jiy, from its 

 running sideways like a crab. It creeps 

 under the tails, and about the groins, of 

 horses, which, at their first coming out of 

 the north, are rendered half frantic by the 

 tickling sensation ; while our own breed 

 little regards them. 



The curious Reaumur discovered the large 

 eggs, or rather pwpce, of these flies as big 

 as the flies themselves, which he hatched in 

 his own bosom. Any person that will take 

 the trouble to examine the old nests of 

 either species of swallows may find in them 

 the black shining cases or skins of the pupm 



