282 J. A. C;. REHN 



general territory east to Montana, while the little-known Oreo- 

 pedes and Crytophylliciis are Sierran endemics, occurring respectively 

 on the eastern and western slopes. Only at high elevations in the 

 Sierras, generally above timberline, occurs the flightless Acrodectes, 

 which is known from the summit and vicinity of Mount Whitney, 

 and which also may be found to have Palearctic affinities. Californian 

 endemic decticid genera of lower levels are Idionotus, Decticita, 

 and Clinopleura. The last-named genus apparently developed from 

 the same basic line as the genus Steiroxys, which is chiefly a Cordill- 

 eran and Great Basin type, with, however, a few records from east 

 of the Rockies (its distribution as a whole is at present poorly 

 understood). It is possible that Clinopleura and Steiroxys may be 

 found to have Palearctic affinities. 



It is possible, and even probable, that a comprehensive study, 

 now outlined, may show that the very complex and greatly dif- 

 ferentiated decticid fauna of western North America represents 

 several lines of infiltration of Palearctic elements, and that they 

 have come into our territory long since the sole eastern representa- 

 tive of the subfamily, Atlanticus, either moved into our territory 

 from eastern Asia, or conversely traveled to the latter area from 

 eastern North America, where today it has a number of distinct 

 specific lines. Clearly, however, a number of our genera of western 

 North American Decticinae, such as Aglaothorax, Neduba, Zacy- 

 cloptera, Capnobotes, and Plagiostira, have no approximate counter- 

 parts in the Palearctic region, while others, such as Eremopedes, 

 Pediodectes, Ateloplus, Idiostatus, and Idionotus, exhibit almost as 

 well-marked differences and represent distinct lines from the many 

 Old World genera of the subfamily. Certainly a very considerable 

 period of time, isolation, and evolutionary pressure and oppor- 

 tunity has been required to make evident what we see in our western 

 American Decticinae. 



Family Gryllacrididae. The Gryllacrididae, for which the most 

 generally used vernacular name is "camel crickets," are an ex- 

 tremely complex and difficult group systematically. Their ancestral 

 stock, according to Zeuner, who is probably our most able scholar 

 in this respect, diverged from the Protorthoptera probably in the 

 Mesozoic. What he regards as ancestral stocks have been found in 

 the Upper Jurassic of Solenhafen, although typical Gryllacrididae 

 are not known from earlier than the Tertiary. Several genera from 



