168 The Rev. L. Jenyns on the Common Bat of Pennant. 
stances; but these, after having once withdrawn, are not gene- 
rally seen again till the ensuing season*. Most probably their 
continuance abroad is regulated by the supply of food, which 
itself must depend in some measure upon the state of the 
weather: and from the circumstance of our common Bat being 
so much on wing in the dead season of the year, it seems likely 
that the prey of this species may consist chiefly of gnats and 
small Tipulide, which do not appear to be affected like other 
insects by the cold of winter. 
I have only to add in conclusion, that if I am right in my 
remarks upon the identity of our Common Bat with the Pipis- 
trelle of French authors, the true Vespertilio murinus must neces- 
sarily be suppressed as a British species, at least till further 
observation shall have detected it in this country. 
* The early retreat of the Noctule was particularly noticed by White, who in his 
Natural History of Selborne (p. 76.) hints at the possibility of its migration. The 
same idea seems to be entertained by Dr. Fleming (Phil. Zool. ii. 99.) ; but as I have 
had this species brought to me from the hollows of trees late in the autumn, and in a 
very reduced state, I cannot assent to this myself, Pennant also (Hist. Quad. ii. $17.) 
mentions one that was taken during winter in Flintshire. Moreover, it may be added, 
that the Bat, though capable of supporting itself in the air for a considerable time by 
means of its flying membranes, seems on the whole but ill calculated for performing 
XVL De- 
