NATURAL HISTORY OF SELBORNE. 155 
[It will be proper to premise here that the sixteenth, eighteenth, 
twentieth, and twenty-first 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, 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 
1. HIPPOBOSCA HIRUNDINIS. 2. NIRMI. 
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 peculiar lice; but the 
* “See Ulloa’s Travels.” 
t+ Or Nirmi, now fully described in the ‘‘Monographia Anoplurorum Britanniz,’’ 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 infest many of the foreign 
mammalia. This volume would be of great interest, and only requires sufficient excourage- 
ment to be brought out. 
