232 University of California Publications in Zoology  [Vou. 17 
Hasirs or Bars 
The habits of our California bats are, unfortunately, but little 
known. The time and extent of the breeding season, migration and 
hibernation, the choice of diurnal retreats, and favorite feeding- 
erounds, the methods of securing and devouring prey, the nature of 
the food, the economic value of bats—these are only a few of the many 
points on which data are as yet almost wholly lacking. 
The seanty material which the writer has been able to gather 
regarding the habits of our bats is given in the succeeding pages under 
the subheading Natural History, at the close of the description of each 
species. However, certain general topics, such as migration, are sep- 
arately discussed in the paragraphs immediately following. 
Migration.—Recorded observations concerning the migration of 
bats are few, and in California the study of bat migration has not 
progressed beyond the observation that some species which are com- 
mon in fall and winter are not to be seen during the summer months, 
while others known to oceur during the summer are apparently absent 
during fall and winter. 
Among the bats of California are found three species which occur 
in suitable localities throughout the whole United States and in British 
Columbia. These are the Silvery-haired Bat (Lasionycteris noctiva- 
gans), the Hoary Bat (Nycteris cinercus), and the Red Bat (Nycteris 
borealis), of which latter species several races occur. These three 
bats are known to be migratory in at least portions of their ranges. 
and some of the facts relating to their migration are of general 
interest. 
As Dr. C. Hart Merriam (1887, p. 85) points out, all North Amer- 
ican bats, except in those places where their habits have been modified 
by proximity to man, may be classed either as cave-dwelling or as 
tree-dwelling, according to the places in which they spend the day. 
As a rule, the cave-dwelling species live in large colonies, while the 
tree-dwelling species live singly or in but small companies. Now it 
is well known that the temperature in caves is little affected by the 
condition of the atmosphere outside, while the temperature of holes 
in trees and recesses in the foliage is about the same as that of the 
surrounding air. ‘These three migratory bats are here in California 
foliage-dwellers, exposed as directly as are birds to changes in atmos- 
pheric temperature. 
Merriam gives no details of the extent or exact northward and 
