NATURAL HISTORY 
GukquW, are defolated, it feems, by the infinite fwarms of venom- 
ous mofquitoes, which fill the air, and render thofe coafts infup- 
portable. It would be worth inquiring whether any fpecies of 
hirimdines is found in thofe regions. Whoever contemplates the 
myriads of infefts that fport in the fun-beams of a fummer evening 
in this country, will foon be convinced to what a degree our 
atmofphere would be choaked with them was it not for the friendly 
interpofition of the fwallow tribe. 
Many fpecies of birds have their peculiar lice ; but the hirundines 
alone feem to be annoyed with dipterous infedls, which infeft every 
fpecies, and are fo large, in proportion to themfelves, that they muft 
be extremely irkfome and injurious to them. Thefe are the 
hippobofca hirundinis, with narrow fubulated wings, abounding in 
every neft; and are hatched by the warmth of the bird's own body 
during incubation, and crawl about under it's feathers. 
A fpecies of them is familiar to horfemen in the fouth of England 
vmder the name of forejl-fy ; and to fome of fide-fiy^ from it's run- 
ing fideways like a crab. It creeps under the tails, and about the 
groins, of horfes, which, at their fii-ft coming out of the north, are 
rendered half frantic by the tickling fenfationj while our own 
breed little regards them. 
The curious Reaumur difcovered the large eggs, or rather 
of thefe flies as big as the flies themfelves, which he hatched in 
his own bofom. Any perfon that will take the trouble to examine 
the old nefts of either fpecies of fwallows may find in them the 
black fliining cafes or ikins of the pupa of thefe infeds : but for 
other particulars, too long for this place, we refer the reader to 
V Hi^oire d'lnfe^es of that admirable entomologift. Tom. iv, pi. 1 1. 
« See Ulloai Travels. 
LETTER 
