214 The Natural History of Selborne 



desolated, it seems, by the infinite swarms of venomous mosquitoes, 

 which fill the air, and render those coasts insupportable. It would 

 be worth inquiring whether any species of hirundines is found in 

 those regions. 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 was 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 hippo- 

 boscte hirundinis t 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 pup<e, 

 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 pup# 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. ii. 



