238 University of California Publications in Zoology  [Vou.17 
It has been stated to the author that house cats find the bodies of 
bats unpalatable. No opportunity has been found for experimen- 
tation along this line. 
It is clear that the enemies of bats are few; only one seems to 
make more than slight inroads upon their numbers. This enemy is 
man, who is often guilty of wholesale destruction of individuals of 
eregarious species. Where colonies of bats have taken possession of 
attics, barns, or church steeples they are often ruthlessly destroyed 
when once their squeaking, or the disagreeable odor emanating from 
their haunt, has betrayed them. A simple method of disposing of a 
colony of bats which has proved a nuisance is to board up, or sereen 
over, all the entrances to such retreats in the evening when the occu- 
pants are on the wing. 
Economic VALUE OF BATS AND THEIR CONSERVATION 
Many detailed studies have been made and much written to show 
the value of our insectivorous birds. As much more might be written 
to show the economic value of our bats. For the latter are undoubt- 
edly as important in keeping in check crepuscular and nocturnal 
insects as the birds are in destroying day-flying species. Among the 
insects destroyed there are not only many species which are harmful 
to agriculture, but also disease-carrying inseets, such as the mosquito 
hosts of malaria. 
Dr. C. A. R. Campbell (1918, pp. 1175-1181) has estimated that 
at Mitchell’s Lake, Texas, 90 per cent of the food of bats consists of 
malaria-carrying mosquitoes. At this place Dr. Campbell built a 
bat roost in 1911, and during the succeeding two years, when the roost 
had become populously tenanted, he not only found that the number 
of mosquitoes had decreased materially but also that malaria had 
become much less prevalent in the region. In the neighborhood where 
these experiments were carried on not only were the people much 
annoyed by mosquitoes before the erection of the roost, but stock also 
suffered severely, horses and cattle becoming thin and anemic in spite 
of being well fed. Campbell (1918, p. 1176) believes that the bat 
itself is protected against the depredations of the mosquito by the 
peculiar formation of the hairs, which in the bat are not smooth and 
round, but in appearance likened to a number of morning-glory 
flowers strung on a straw (fig. A). 
Campbell suggests the wisdom of erecting roosts, similar to the one 
