310 University of California Publications in Zoology  [Vou. 17 
At Cushenbury Springs, on the desert slope of the San Bernardino 
Mountains, J. Grinnell (1908, pp. 159-160) found these bats common 
in the early part of August. They appeared at late dusk among the 
cottonwoods and over the pasture, and swarms of them were to be seen 
darting about over the surface of a small pond, frequently dipping 
down and touching the surface of the water as if drinking. The five 
specimens secured at that time and place were very fat. 
In 1908, Grinnell and Swarth (1913, p. 382) found these bats 
abundant along Palm Canon and in the neighborhood of Dos Palmos 
Spring, on the desert slope of the San Jacinto Mountains. Here they 
were found emerging from the crevices of rocks at early dusk. This 
was the only species of bat seen abroad after sunrise and before 
sunset; in fact one individual was seen in flight about 9 a.m. in the 
bright glare of the forenoon sun. 
In the spring of 1910 J. Grinnell (1914, pp. 267-268) found the 
western bat abundant along the Colorado River between Needles and 
Pilot Knob. Here it was noticed that the bats were to be found only 
in the neighborhood of cliffs and rocky hillsides. 
No instances of the occurrence of this bat in or about buildings 
or as hanging up on the foliage of trees, have been recorded. 
Specimens in the Museum of Vertebrate Zoology have been taken 
in all the months from February to August, inclusive, and there is 
also a specimen taken at Palm Springs in December. Winter collect- 
ing would probably reveal the presence of this species throughout 
the year in at least the lowest parts of its range. Stephens (1906, 
pp. 269-270) states that very few western bats remain in California 
in winter. ‘‘The northward migration is at its height about the end 
of March, at which time’’ the bats are abundant about certain springs 
along the western border of the Colorado Desert. 
The number of young and time of breeding are indicated by the 
following data, taken from specimens in the Museum of Vertebrate 
Zoology secured in Kern County in the summer of 1911: no. 16308, 
taken June 18, contained two embryos; no. 16309, taken June 19, 
contained two embryos; no. 16310, taken June 20, contained two em- 
bryos; no. 16312, taken June 23, contained two embryos; no. 16313, 
taken July 1, contained two embryos; no. 16314, taken July 11, 
contained one embryo. 
a aa 
