368 University of California Publications in Zoology (Vou. 17 
P 
(MS), when encamped in April, 1912, near Marysville Buttes, Sutter 
County, noted bats of this species flying down the cafion each even- 
ing. They appeared shortly after 6:45 p.w. OC. H. Richardson (MS) 
took six male N. mexicanus from spaces between the sheathing and 
shakes on a barn beside a slough near Los Banos, Merced County, 
on March 25, 1911. He writes: ‘‘This was evidently an old roost, 
for the dung lay thick upon the floor. There were many bats present, 
to judge from the amount of squeaking and the odor.”’ 
Several specimens of this bat have been sent to the Museum of 
Vertebrate Zoology from the attic of a schoolhouse at Fresno. 
Heller (in Elhot, 1904a, p. 320) found Nyctinomus mexicanus 
common in the spring of 1902 in Palm Canon, near Palm Springs, 
Riverside County. He also found several hundred living in the 
garret of one of the old buildings at Fort Tejon, Kern County. 
Specimens secured during November and December from the attic 
of a blacksmith shop at Concord, Contra Costa County, and sent to 
the Museum of Vertebrate Zoology, were excessively fat. The males 
examined had very small testes. Specimens secured from the same 
colony January 31 were very thin. In one of the males examined the 
testes were shghtly enlarged, indicating the possibility of spring 
mating in this species. The stomachs of four specimens were 
crammed with the remains of insects, flies and small beetles, too finely 
triturated for identification. I do not think that these bats had 
hibernated but that the loss of fat was due to the seareity of food, 
caused by the frosty weather of December and January. 
Along the Colorado River between Needles and Yuma, in the 
spring of 1910, Museum collectors found the species not uncommon. 
In the neighborhood of Mecca, Riverside County, the species was 
found during the spring of 1908, and one specimen was collected from 
a colony found in a cave on Echo Island in Salton Sea. 
On the evening of January 1, 1915, J. Grinnell (MS) noted several 
bats flying at El Portal, Mariposa County, 2000 feet altitude. One 
of the two examples shot proved to be Nyctinomus mexicanus. This 
specimen, a female, weighed 11.5 grams. Specimens and records at 
hand establish the presence of the Mexican free-tailed bat in the same 
general areas of the state throughout the year. It is therefore safe 
to infer that this species is but slightly or not at all migratory. 
On October 27, 1916, J. R. Pemberton and J. Grinnell investigated 
a colony of bats (pl. 14, fig. 2) oceupying the attie of a brick house 
at San Bernardino, the home of R. B. Herron. Dr. Grinnell records 
(MS) his observations as follows: 
