120 ANIMAL LIFE OF CARLSBAD CAVERN 



groups of mammals on earth, and perhaps are among 

 the oldest. In North America there are approximately 

 eight families, seventy-three genera, and two hundred 

 and fifty species of bats. The number of individuals is 

 enormous, corresponding well with the numbers of 

 birds, and these are scattered over the continent partly 

 in accordance with the insect population, or with certain 

 groups of insects, on which they largely subsist. 

 Naturally the number of species and individuals is 

 greater in the south than in the north. 



All of our North American bats, north of the tropics, 

 are entirely insectivorous, feeding on nocturnal insects 

 and to an important degree controlling their abundance, 

 just as many birds do the diurnal insects. It is con- 

 ceivable that without bats many kinds of vegetation 

 would be wholly devoured by insect pests, just as with- 

 out the birds our crops and forests would suffer. It 

 seems not unreasonable to credit bats with an economic 

 value to man approximately equal to that of the birds. 



The guano bats belong to a southern group, with 

 tails extending about an inch beyond the membrane, 

 with short, wide ears, close, oily fur of a sooty color, 

 and with a strong odor that is unmistakable. They 

 are of medium size, spreading about twelve inches 

 across the wings. 



JACK-RABBIT BAT 



Corynorhinus macrotis pallescens (Figs. 1^3 and 44) 



These long-eared bats were found in the McKittrick 

 Cave, twenty miles west of Carlsbad, on April 15, still 

 hibernating, hanging cold and torpid to the roof of the 



