MAMMALS OF PE^fNSYLVANIA AND NEW JERSEY. 209 



lucifugus " exceedingly abundant in a cave near Hillside, Westmoreland Co., 

 Pa,, in February, 1900, roosting in clusters containing hundreds of individu- 

 als." Dr. Abbott states that these bats " appear about the first of May in N. 

 J., and as soon as it is dusk, commence a flight that lasts the greater part of 

 the night, killing in the time an mdescribable number of insects." The insect 

 diet of our bats is a feature quite worthy of consideration, as they are exclu- 

 sively insectivorous, so far as we know. They devour a great quantity of 

 mosquitoes, as 1 have plainly observed before dark while sitting in a swarm of 

 these pestiferous insects, the bats snapped them up within a few feet of my 

 head. Probably nothing comes amiss which can be readily seized, but the 

 relatively small size of the mouth of bat as compared with that of the swifts, 

 swallows and night-hawk would confine it to small species. The finely broken 

 elytra or wing cases of beetles can be found in their excrement. As the bat 

 chews its food before swallowing, it is difficult to identify the contents of its 

 stomach. The flight of the little brown bat is much more rapid than that of 

 Pipisirellus, more erratic than that of the small red bat, and the animal is easily 

 distinguished from the large brown bat by its small size. As compared with 

 the flight of the silver-haired bat I cannot distinguish it. Most of our bats 

 have one or rarely two young. These cling by their mouths to the teats of 

 the mother until large enough to grasp her body. Thus laden, she pursues 

 her nightly avocations until they can be left " hung up" in some secret place 

 till her return. The method of alighting is first by the wing or arm hooks 

 head upward, assisted by the hind feet. As soon as the latter are firmly 

 implanted the bat turns head downward and hangs by the sharply recurved 

 nails of the hind feet. Frosty weather in autumn, or such as makes insects 

 dormant, has the same effect on all our bats in varying degrees. By this time 

 they have become excessively fat, and in this condition go into hibernation in 

 such places as are not subjected to very low winter temperatures, preferably 

 caves. From these they emerge in spring with the reappearance of noctur- 

 nal insect life. Sometimes they come out during a February thaw, and go 

 back again until April. The females are said to become gravid in the fall, 

 and bring forth in the spring, an unusually long period of gestation, if true. 

 A more or less extensive migration of some species of bat from the Canadian 

 zone southward is supposed to occur. Especially is this the case with the 

 genus Lasuirus, including the red and hoary species of our list. The voice 

 of all our bats resembles the combination of hissing sharp squeaks and the 

 clicking or gritting of teeth. They not only utter these when abused, but 

 also in their encounters and gambols in the air, and when a large cluster are 

 dislodged in a cave, these shrill, piercing cries, as they reassemble, are very 

 disagreeable and sometimes painful to the ear. 



Description 0/ species. — See under preceding species, M. lucifugus. 



Specimens examined or recorded. — Allegheny Co., Carnot, " A few speci- 



