OF SELBORNE 155 



[It will be proper to premise here that the sixteenth, eighteenth, 

 twentieth, and twenty-flrst letters have been published already in 

 the Philosophical Transactions : but as nicer observation has 

 furnished several corrections and additions, it is hoped that the 

 republication of them will not give offence ; especially as these 

 sheets would be very imperfect without them, and as they will be 

 new to many readers who had no opportunity of seeing them when 

 they made their first appearance.] 



The hirundines are a most inoffensive, harmless, enter- 

 taining, social, and useful tribe of birds : they touch no 

 fruit in our gardens ; delight, all except one species, in 

 attaching themselves to our houses ; amuse us with their 

 migrations, songs, and marvellous agility ; and clear 

 our outlets from the annoyances of gnats and other 

 troublesome insects. Some districts in the south seas, 

 near Guiaquil,* are 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 particular 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 truly irksome 

 and injurious to them. These are the hippoboscx hirun- 

 dinis 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, 



* See UUoa's Travels. 



