90 NATURAL HISTORY 



Though I delight very little in analogous reasoning, 

 knowing how fallacious it is with respect to natural history ; 

 yet, in the following instance, I cannot help being inclined 

 to think it may conduce towards the explanation of a diffi- 

 culty 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 1 (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 highflying gnats, 

 scarabs, or Phalcence, 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 2 clamoured on to 

 October the thirty-first : since which I have not seen or 

 heard any. Swallows were observed on to November the 

 third. 



1 The little bat appears almost every 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 ; are a rare species 

 with us. G. W. 



2 Stone-curlews, (Edicncmus crcpitans. The true curlew, Numenius 

 arcuutus. was not observed at Selborne. ED. 



