180 
NATURAL HISTORY 
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 in- 
sects, which infest every species, and are so large, in pro- 
portion to themselves, that they must be extremely irksome 
and injurious to them. These are the Hippohoscce hirun- 
dinis,^ 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 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 
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 des 
Insectes^' of that admirable entomologist, tom. iv. pi. 11. 
^ Craterina hirundinis, Olfeks. 
^ In the ISTew Forest, whence its name of forest fly, the Hinpohosca 
equina, Linn., abounds in such profusion that Mr. Samouelle states, in 
his "Entomologist's Useful Compendium," that he has obtained from 
the flanks of one horse six handfuls, which consisted of upwards of a 
hundred specimens. He adds, " Mr. Bentley informs me, from obser- 
vations he made in the summer of 1818, while in Hampshire, that the 
Hippohoscce are found in a considerably greater abundance on white 
and light-coloured horses than on those of a black and dark colour ; 
and this observation was confirmed by the stable-keepers in the vicinity 
of the Forest."— Ed. 
