AMERICAN BATS — ^HANDLEY 173 



and other animals might account for such a loss and thus would be 

 the primary limiting factor. Rice (1957, p. 30) postulated that 

 predation by rat and corn snakes, opossums, owls, and cockroaches 

 was the most important mortality factor among populations of 

 My Otis austroriparius in Florida. 



The possibility of antisocial tendencies and consequent need of 

 some degree of privacy from other species of bats might be a limiting 

 factor for P. townsendii where roosting places are not abundant. 

 Pearson, etal. (1952, p. 317) believed it most likely that the popula- 

 tion level of this species in California depended upon the number 

 of suitable winter roosting sites and the number of summer roosting 

 sites surrounded by adequate feeding territory. Their data indicated 

 that disease, predation, and amount of food and water probably did 

 not limit the Californian populations. They observed that colonies 

 remained static in size, year after year, and believed that a species 

 population increase might depend on establishment of new nursery 

 colonies. 



How new nursery colonies become established is not known. 

 Pearson, et al. (1952, p. 317) determined that when a satisfactory 

 nursery site becomes available near an already-established colony, 

 the colony does not divide to make use of both sites, but uses either 

 one or the other, or alternates between the two. Consequently, they 

 thought, for a new nursery colony to become established, some 

 females either through chance, faulty navigation, or some inner 

 drive must find a suitable roosting place outside of the range of an 

 existing colony. Furthermore, they believed it necessary for several 

 females to arrive at this place almost simultaneously if gestation 

 were to proceed normally, since females are gregarious and may 

 depend upon clustering to keep their body temperatures high. 



These hypotheses might serve to explain the evident slowness of 

 Plecotus in reoccupying apparently suitable territory to the north 

 of their present geographic range since the retreat of the Wisconsin 

 glaciers. 



Parasites and disease: No ticks, lice, fleas, or bedbugs have 

 been reported on P. townsendii, and this bat is not particularly noted 

 for heavy infestations of other ectoparasites. 



Winged parasitic flies of the family Streblidae (Trichobius cory- 

 norhini Cockerell and Trichobius quadrisetosus Kessel) appear to be 

 encountered most often. I have noted flies of this family on specimens 

 of Plecotus from Veracruz and West Virginia. Others have reported 

 them as follows: Sprague (1938, p. 500) an infestation in Oklahoma, 

 Wilson (1946, p. 86) in West Virginia, Dalquest (1947, p. 30) no 

 more than one per bat in California, Krutzsch (1955, p. 458) up to 

 three or four per bat on fur and membranes of specimens from "western 



