172 ANIMAL LIFE OF CARLSBAD CAVERN 



derived from the bat guano, dead bats and other 

 animals, and such dead vegetable matter as is washed 

 in through the two natural openings. 



During the twenty-year period when the guano was 

 being removed from the cave, many workmen with food 

 and clothing, lumber, machinery, and sacks were em- 

 ployed in the upper level of the cave, and some of the 

 materialsleft at that time, 1901 to 1921, and other refuse 

 left by visitors since, may have attracted some of the 

 insects and spiders. Most of the species collected, how- 

 ever, seem to be the more ancient inhabitants of the 

 cave. 



When logs, stones, or boards are moved from the 

 surface of the ground, insects and other small creeping 

 things, beetles, spiders, bugs, centipedes and millipedes 

 are often seen scurrying here and there in a frantic 

 endeavor to find some dark retreat where they can hide 

 away from the fight. The longer the log, stone, or 

 board has lain, the more numerous will be the small 

 things living under it, if moisture and food conditions 

 are favorable. Likewise in old abandoned burrows of 

 mammals, in hollow banks, or in cellars, it is the rule 

 and not the exception to find an abundance of insects 

 and other small life hiding away from the light. Some 

 of these are merely nocturnal species, which roam over 

 the surface of the ground at night and take refuge by 

 day in dark, moist cavities, while others more or less 

 permanently inhabit such places, finding both food and 

 lodging as well as protection from a host of natural 

 enemies. While other insects may be diurnal and 

 terrestrial, arboreal, arid or aquatic, according as each 



