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 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 particular 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 truly irksome and injurious to them. These are the hippoboscae 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 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 pupae, of these flies as big as the flies themselves, which he hatched in his own bosom. Any person that will take the troupe to examine the old nests of either species of swallows may find in them the black shining cases of the pupae 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.
