290 J. A. G. REHN 



ated at different periods from the line represented by G. campodei- 

 formis (the genotype), which ranges in the Cordilleran region from 

 as far north as Jasper Park, Alberta, to the Yellowstone National 

 Park. The fact that the Cascadan and Sierran species are more 

 divergent from campodeiformis, would indicate to me that these 

 more southern representatives have been established as divergent 

 entities for a longer time. The greatest known specific differenti- 

 ation in the family has taken place in North America, and it is fair 

 to assume that the family had its beginnings in western North 

 America, and that ancestral lines probably traveled eastward over a 

 Bering Sea land bridge well in the past. We have parallel cases in 

 the Orthoptera, such as the decticid genus Atlanticus and the 

 acrid id Zubovskya. 



Superfamily Phasmatoidea 



(Cheleutoptera of some authors) 



The Phasmatoidea, or "walking-stick insects," are a very dis- 

 tinctive assemblage, much more diversely developed in the number 

 of genera and species in certain tropical areas than in more temperate 

 ones. The areas of optimum differentiation are the Neotropical, 

 the Indo-Malayan, and the Australian. Africa has in proportion a 

 relatively smaller representation, even its great forested area 

 having a much less marked diversity than similar regions in the 

 Neotropical and Indo-Malayan regions. 



In North America we find representations of four entities of 

 higher rank (variously regarded as families or subfamilies), one of 

 which, elsewhere entirely Neotropical, occurs in the southeastern 

 and central United States but does not enter more western territory. 

 One very distinctive line, which is almost universally regarded as a 

 family, the Timemidae, with the single genus Timema, is as far as 

 known restricted to certain areas of the western United States. 

 Timema possesses a number of unusual, possibly primitive, char- 

 acters, and its six species are known from well-separated areas in the 

 mountainous areas of California and of extreme southeastern 

 Arizona. The species are, as far as known, tree or bush dwelling. 

 The family is clearly an autochthon of the general area where it is 

 now found, and it shows a pattern of distribution essentially 

 parallel to that of the three genera composing the Morseinae of the 

 Eumastacidae. Perhaps as our knowledge becomes more compre- 



