92 ECOLOGICAL FOUNDATIONS OF ZOOGEOGRAPHY 



in underground waters and reach the surface in springs, in part as 

 empty shells, in part also alive. With great constancy of generic 

 characters, they are very variable (Fig. 8), and the species form 

 geographical groups, each type of Lartetia corresponding to a special 

 type of spring. 73 Of the pulmonate snails the genus Zospeum is widely 

 distributed in caves, and is broken up into 30 or 40 species. 



Beautiful examples of the effect of isolation in caves are presented 

 by the cave beetles in the limestone caves of middle and south Europe. 

 The carabid genus Anophthalmia, a subgenus of Trechus, is repre- 

 sented by numerous species in caves, and these form subspecies con- 

 fined to a single or to a few neighboring caves. The silphids of caves, 

 subfamily Leptoderinae, are so split up that almost every cave has 

 its special species, while these represent a number of genera, though 

 the latter form a continuous series, and are not sharply differentiated. 74 



p IG . 8. — Various species of Lartetia, from left to right: L. pellucida, photophila, 



putei, and acicula. After Brauer. 



Widespread species form local races and subspecies without special 

 isolation. Thus the lions, zebras, antelopes, and giraffes are split into 

 a number of geographic races, which are in part sharply defined and 

 in part connected by transitional forms. The butterflies of Celebes 

 are spread throughout the island, but each of the four peninsulas has 

 its own local forms. 75 An endless series of geographic races is present 

 in the Apollo butterfly (Parnassius apollo) , which ranges from Syria 

 to Finland and from Austria to beyond Lake Baikal. The geographic 

 variation in this butterfly is favored by an extraordinary individual 

 variability. The situation is similar with the goat chafer Dorcadion. 

 Lack of wings and slowness of motion hinder its migration, so that 

 numerous local races have arisen; ten varieties of D. fuliginator are 

 listed in central Europe. 76 The South American butterflies of the 

 family Erycinidae are. extremely restricted to their places of origin 

 by a tendency to avoid flight. The specimens of a given locality re- 

 semble each other like coins from the mint, but even the most 



