84 NATURAL HISTORY OF SELBORNE. 
there; or is it the constant practice of the aquatic-rat to forsake 
the neighbourhood of the water in the colder months ? 
Though I dehght very Httle in analogous 
reasoning, knowing how fallacious it is with 
respect to natural history ; yet, in the fol- 
lowing instance, I cannot help being in- 
clined to think it may conduce towards the 
explanation of a difficulty that I have men- 
tioned 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 common Swift 
beginning of August. 
The great large bat* (which by the bye is at present a non- 
descript in England, and what I have never been able yet to 
procure) retires or migrates very early 
m 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 phalcencB, 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 curlewsf clamoured on to Octo- 
ber the thirty-first ; since which I have not seen or heard any. 
Swallows were observed on to November the third. 
* The little bat appears almost ever}' month in the year ; but I have never seen the large ones 
till the end of April, nor after July. They are most common in June, but never in any plenty, 
being a rare species with us. The pipistrel bat {V. pipistrella) is the species seen on the wing 
at all seasons. — Ed. 
t Thicknees {cediaiemus Eiu-opoeus) are of course here intended, the curlew genus {numenius) 
being very distinct. — En. 
