Bats 
269 
or Fruit-eating Bats, distinguished by the possession of a claw 
to the second digit as well as to the pollex, the other, the 
Microchiroptera, containing the other five families. In Colo- 
rado, however, we have representatives of only two families, 
both belonging to the Insect-eating Bats or Microchiroptera. 
Habits of Bats. — Bats are nocturnal and crepusular, ap- 
pearing only towards dusk, and rarely seen flying during the 
day. During the day they hide in caves, crevices in rocks, in 
or about buildings, or in the branches of trees, suspending 
themselves by the hind feet and hanging head downward. 
The Colorado species are insectivorous, but there is a group 
of bats, usually of very large size, which subsists entirely 
or nearly so on fruit. Besides these there are bats which 
have a mixed diet of fruit and insects, and in South America 
are found the noted Vampire Bats, which live by sucking the 
blood of animals, and have their digestive apparatus greatly 
modified, the oesophagus being very narrow, and the stomach 
slender and intestine-like. 
Some species at least of the bats are supposed to migrate 
at the approach of cold weather, while others seem to 
hibernate, but at present but little seems to be known on 
the subject. A. H. Howell, in Proc. Biol. Soc. Wash., xxi., 
p. 35 (1908), speaks of seeing bats flying over a suburb of 
Washington, D. C, Sept. 28, 1907, between 9 and 10 a.m. 
During this time over a hundred bats were noted, all flying 
with the wind, which was southwest. They did not fly in 
flocks but singly. They were at height estimated as varying 
from 150 to 400 feet above the ground, which distance made 
it quite impossible to identify the species, though with a 
field glass it could be seen that there were at least three sizes 
represented. See also beyond under Myotis californicus. 
The flight is usually erratic, the animals twisting and 
turning in every direction in pursuit of their prey, the night- 
flying insects. This peculiarity of flight makes it rather 
