116 
NATURAL HISTOEY OP SELBORNE. 
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, entertaining, 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 sun-beams 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 hippoboscce 
hiTundinis, with narrow subulated 
wings, abounding in every nest ; 
and are hatched by the warmth of 
the bird's own body during incuba- 
tion, and crawl about under its 
feathers. 
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 Eeaumur discovered the large eggs, or rather pupce, 
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 pupce 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." 
* "See Ulloa's Travels." 
t Or Nirmi, now fully described in the ' ' Monographic. Anoplurorum Britannise, ' 
by Henry Denny ; who has also in readiness for publication materials sufficient 
for a volume upon the parasites of exotic species, as well as on those which infect 
many of the foreign mammalia. This volume would be of great interest, and only 
requires sufficient encouragement to be brought out. 
1. HIPPOBOSCA HIEUNDINIS. 
2, NIRMI. 
