NATURAL HISTORY OF SELBORNE 1 29 



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 hippobosccs 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 com- 

 ing 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<z, 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//^ 

 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." 



NOTES 



1 The white owl does hoot, although it is not its most frequent cry. 

 G. C. D. 



2 See Ulloa's "Travels." G. W. 



LETTER XVI 



SELBORNE, Nov. zM, 1773. 



DEAR SIR, In obedience to your injunctions I sit down to 



give you some account of the house-martin, or martlet ; and if 



my monography of this little domestic and familiar bird should 



happen to meet with your approbation, I may probably soon 



10 



