CHAPTER XXVII 

 SUBTERRANEAN ANIMAL LIFE 



The environment to which animals of subterranean spaces are 

 exposed is also highly peculiar, and does not fit into the schematic 

 summary of animal communities given at the opening of the preceding 

 chapter. Such spaces include not only caves with their waters, but also 

 crevices and holes in rock, mine galleries, cellars, catacombs, aqueducts, 

 ground waters, and deep springs. It is from these varied sources, some 

 of them inaccessible to investigation, that the faunae of the larger caves 

 are in some measure derived. Limestone mountains, especially like the 

 Karst or Alb of Europe or like the Ozarks in North America, are 

 riddled with cavities and channels, in which run a whole system of 

 small and large watercourses, which may finally emerge as large 

 springs. These spaces harbor a fauna characterized by a number of 

 parallel or convergent correlations which fit their peculiar habitat. 



The cave animals are not all equally bound to a subterranean life. 

 They may be divided into three groups: exclusively subterranean 

 forms, confined to such situations, and found elsewhere only when 

 carried out by accident or force, so-called troglobic forms ; occasional 

 cave inhabitants, which also occur on the surface, but are less regu- 

 larly to be found in caves; and accidental cave dwellers. 



Examples of the accidental appearance of the first group at the 

 surface are the occurrence of the olm {Proteus) in the Zirknitz Lake, 

 or the appearance of the cave amphipod Niphargus 1 or the cave snail 

 Lartetia 2 in springs. The second group is a varied one ; many are wide- 

 spread forms, "ubiquists," which also enter caves; thus the five most 

 common cave copepods* are among the most widely distributed species 

 of the genus, and occur also in the depths of lakes. 3 Other forms which 

 are able to live both above and below ground may be much more 

 abundant in caves than elsewhere, like the mite Linopodes longipes, 

 the opilionid Nemastoma lugubre, and the springtail Macrotoma viri- 

 descens. 4 Such forms exhibit a transition toward confinement to cave 

 life. Other species may be rare in caves, like the planarian PL montene- 

 grina which is everywhere found in brooks and more rarely in subter- 



* Cyclops viridis, strenuus, serrulatus, fimbriatus, and bicuspidatus. 



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