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 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.
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