1918 | Grinnell: A Synopsis of the Bats of California 369 
I found just one species, Nyctinomus mexicanus, though Mr. Herron declares 
there are at least three kinds present, at different seasons of the year. I went 
all through the attic and all I saw distinctly, flying or in different ‘‘colonies,’’ 
were of the above species. There are now at least 1000 bats, clinging together 
in patches in the peak of the roof, or crowded into crevices between the ridgepole 
and the shingles. Along the floor is a longitudinal heap of guano 6 inches to 
1% feet high. Herron says that he has taken out five grain sacks of the 
guano at one time, and used it about the garden as fertilizer. The bats ‘‘chuckle’’ 
continually, a subdued chorus of talking sounds. There are very few of the 
shrill squeaks. The animals crawl, back upwards, as far as they can get. The 
lower ones crowd against the upper ones, the latter squeezing farther into the 
crevices, the whole mass in continual agitation. When thoroughly disturbed 
many took flight, and the fluttering wings and occasional collisions with me (or 
attempts to alight) gave a weird impression. 
Mr. Herron thinks these bats migrate—they seem to be entirely gone for three 
or four months, in cold weather, and then all at once they come in. ‘‘In summer 
time there are three kinds, a big broad-winged one, a little narrow-winged one, 
and this one.’’ 
Sun sets at 4:57. Perfectly clear weather. First bat out at 5.04. At 5:07, 
27 had come out. At 5:10, 95 more had come out. At 5:15, 120 more had 
come out. At 5:30, when it had gotten too dark for me to count longer, 1367 
more had come out. Total counted, 1609. 
Although there were three gable ends, each with a small slatted ventilator 
window, all the bats came out of the west-facing one. Mr. Herron says the 
first usually comes out just before the sun sets, and all are out in about half an 
hour. He thinks there are as many as 5000 there in midsummer. Just before 
they came out, in little squads of 10 to 50, I heard a low chuckling chorus at 
the grating; then the crowd began to pour out. 
Two female Mexican free-tailed bats taken by Ferris and Storer 
7 
at Coulterville, Mariposa County, June 7, 1915, each contained one 
large embryo. 
Twelve specimens of Nyctinomus mexicanus secured by Mr. Joseph 
Dixon at Limekiln, Eldorado County, between August 3 and 6, 1916, 
were females and varied in weight from 11 to 15 grams. Dixon states 
(MS) that the mammary glands of these bats were full of milk, 
although the glands of adult individuals of Eptesicus and Myotis 
taken at the same time were undeveloped. 
Genus Eumops Miller 
Ears very large, rounded or squarish in outline, joined across 
forehead, usually extending shghtly beyond nostril when laid forward, 
the anterior margin without horny processes; antitragus distinet but 
not thickened, keel greatly developed, flattened and expanded at edge ; 
tragus small, flat, its upper edge truncate or rounded. Lips full and 
expanded, not conspicuously wrinkled. Muzzle pad well developed, 
deeply emarginate above, its upper edge and median ridge with 
minute horny processes and small spoon hairs. Wings, feet and tail 
as given for the family. 
