EUEOPEAN ANTS IN CALIFORNIA 217 



species must have been established in America for long periods 

 past, as their range extends inland in a north-eastward direc- 

 tion beyond the Rocky Mountains. 



Instances of specific identity in the two widely separated 

 regions of California and southern Europe are to be found 

 in .several groups. Professor Kraepelin * reports, for example, 

 that the scolopendrid Theatops erythrocephalus is such a 

 case. From California it has spread as far as Oregon. 

 In southern Europe it is known from Portugal, Italy, 

 Dalmatia and Hungary. The genus Theak>ps is confined to 

 North America, including the Sandwich islands, and southern 

 Europe. 



A member of the order Palpigradi, a minute creature 

 somewhat resembling a scorpion in shape, has been observed 

 in Texas and named Koenenia wheeleri after Professor 

 Wheeler. Two other members of the genus are known from 

 South America, one from Chile, the other from Paraguay. 

 But the nearest relations of the North American form ar,e evi- 

 dently Koenenia mirabilis of Sicily and Tunis, and K. draco of 

 the Balearic islands. The only two other species live in Siam.f 

 We thus have in this ancient group again the same intimate 

 affinity between southern Europe and south-western North 

 America as in some ants, beetles and butterflies, showing 

 clearly that the same potent cause, which is certainly not acci- 

 dental distribution, has contributed to bring it about. In 

 order, however, to make quite sure that these are genuine 

 instances of migration on a land surface, and not due to 

 occasional or accidental transport, let us now examine care- 

 fully the range of a large fresh-water form and endeavour to 

 trace its origin. 



Fresh-water crayfishes, as Dr. Ortmann remarks in his 



excellent account of them, do not possess any exceptional 



means of dispersal. They are restricted to fresh water and 



cannot exist out of it, neither in salt water nor on land. 



Moreover, they do not possess, during any stage of their life 



history, means or devices which might favour their passive 



transport from one fresh -water system to another. The whole 



character of their range is opposed to the assumption that 



* Kraepelin, K., " Revision der Scolopendriden," pp. 6466. 



t Hansen, H. J., "On Koenenia." 



