following instance, I cannot help being inclined to think it may conduce towards the explanation of a difficulty that I have mentioned before, with respect to the 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-by 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 phalænæ, 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.
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
