170 INSECTS ON BIRDS. 



mosquitoes, which fill the air, and render those coasts 

 insupportable. It would be worth inquiring, whe- 

 ther any species of hirundines is found in those re- 

 gions. Whoever contemplates the myriads of insects 

 that sport in the sunbeams of a summer evening in 

 this country, will soon be convinced to what a degree 

 our atmosphere would be choked with them were it 

 not for the friendly interposition of the swallow 

 tribe. 



Many species of birds have their peculiar lice; 

 but the hirundines alone seem to be annoyed with 

 dipterous insects, which infest every species, and 

 are so large, in proportion to themselves, that they 

 must be extremely irksome and injurious to them. 

 These are the hippoboscce hirundinis, 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-fly, and, 

 to some, of side-fly, 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 pupa, 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 

 pupte of these insects; but, for other particulars, 

 too long for this place, we refer the reader to 

 L'Histoire d'Insectes of that admirable entomologist. 

 Tom. iv. pi. 11. 



