The pallid bat is probably the most common and characteristic bat of the citrus belt at the Pacific base of the mountains. Only once, on May 4, 1951, was this bat taken in the mountains. On that night two individuals were collected at 2800 feet in San Antonio Canyon. All of the other specimens and observations were from colonies in old barns and outbuildings in the citrus belt where these bats are found in spring, summer, and fall.
The impression gained by examining many mixed colonies of Antrozous and Tadarida was that the former greatly outnumbered the latter. For example, a small colony of bats in an old barn near San Dimas Wash consisted of about thirty pallid bats and five freetails.
Large numbers of wings of moths of the family Sphingidae, and legs and parts of the heads of Jerusalem crickets (Stenopelmatus fuscus) were beneath an Antrozous night-roosting place in a barn near Upland.
Pallid bats were collected in 1951, from April 16 to October 17 but probably were active in the area into November.
Each of two pregnant females taken two miles northeast of San Dimas on April 20, 1951, carried two embryos 4 millimeters long.
Specimens examined.—Total, 6, distributed as follows: Los Angeles County: 2 mi. NE San Dimas, 1200 ft., 2 (1PC); Ontario, 1100 ft., 4 (3PC).
Family MOLOSSIDAE
Tadarida mexicana (Saussure)
Mexican Free-tailed Bat
This bat, regularly met with in the citrus belt at the coastal base of the range, occurred in small numbers with colonies of Antrozous, and was once found with a colony of Eptesicus near Covina. None of the females taken in April 1951 was pregnant.