156 NATURAL HISTORY OF SELBORNE. 
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 iippobosce 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 acrab. 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 cwn 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 Jufe@ 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. 
LOM. IVs; fal. di,” 
