40 



Routes from the Sea 



porary residents and some of the less highly specialized cave in- 

 habitants are widely distributed and usually apparently cave forms 

 of long standing. . . . The nearest relatives of cave animals are 

 nocturnal, or are dark or shade-loving species. Accidents play no 

 part, or at most a very small part, in the origin of cave inhabitants. 

 Animals have reached caves by active migration into places where 

 they find conditions suitable for their existence. Cave species are 



BATS 



INSECTS 



MITES 



MILLIPEDES 



ARACHNIDS 



ISOPODS 



EARTHWORMS 



FUNGI 



Fig. 7. A cross-section of a cave in Yucatan showing the affinities of 

 the cave animals. 



fitted for cave life before entering caves. Cave species may arise 

 from highly modified animals living outside of caves going direct- 

 ly into the deeper parts of caves, or they may arise gradually by 

 the collecting about the mouths of caves of forms slightly modified" 

 (Banta, 1907). Concerning a recent survey of 41 caves in West 



