invariable early retreat of the _hirundo apus_, or swift,
so many weeks before its congeners; and that not only with us, but also
in Andalusia, where they also begin to retire about the beginning of
August.

The great large bat (which, by-the-bye, is at present a nondescript in
England, and what I have never been able yet to procure) retires or
migrates very early in the summer. It also ranges very high for its
food, feeding in a different region of the air, and that is the reason I
never could procure one. Now this is exactly the case with the swifts;
for they take their food in a more exalted region than the other species,
and are very seldom seen hawking for flies near the ground, or over the
surface of the water. From hence I would conclude that these
_hirundines_ and the larger bats are supported by some sorts of
high-flying gnats, scarabs, or _phaloenae_, that are of short
continuance, and that the short stay of these strangers is regulated by
the defect of their food.

By my journal it appears that curlews clamoured on to October 31st, since
which I have not seen nor heard any. Swallows were observed on to
November 3rd.

LETTER XXVII.

SELBORNE, _Feb. 22nd_, 1770.

Dear Sir,--Hedgehogs abound in my gardens and fields. The manner in
which they eat the roots of the plantain in my grass-walks is very
curious; with their upper mandible, which is much longer than their
lower, they bore under the plant, and so eat the root off upwards,
leaving the tuft of leaves untouched. In this respect they are
serviceable, as they destroy a very troublesome weed; but they deface the
walks in some measure by digging little round holes. It appears, by the
dung that they drop upon the turf, that beetles are no inconsiderable
part of their food. In June last I procured a litter of four or five
young hedgehogs, which appeared to be about five or six days old: they, I
find, like puppies, are born blind, and could not see when they came to
my hands. No doubt their spines are soft and flexible at the time of
their birth, or else the poor dam would have but a bad time of it in the
critical moment of parturition, but it is plain they soon harden; for
these little pigs had such stiff prickles on their backs and sides as
would easily have fetched blood, had they not been handled with caution.
Their spines are quite white at this age; and they have little hanging
ears, which I d