DERMAPTERA AND ORTHOPTERA 291 



henslve we may find that this, and similar correlations, indicate 

 parallel spreads of widely distinct entities, but of similar faunistic 

 histories. While it is purely a postulate, it is my belief that the 

 distributional evidence here reflects Pleistocene conditions, and 

 heavier precipitation and lower temperatures then over extensive 

 areas now largely desert or semi-desert, and that the genesis of the 

 Timemidae probably took place in California very much before 

 the Pleistocene. 



The subfamily Pachymorphinae, a group widely spread over the 

 world is represented in much of the western half of North America 

 by the genus Parabacillus. Its range extends northward over the 

 Great Plains to the Dakotas and elsewhere into New Mexico, Ari- 

 zona, southern Nevada, and southern California. While it also ex- 

 tends a considerable distance into Mexico, its greatest distribution 

 is northward over the Great Plains, and I would regard it as Cam- 

 pestran in origin, with closest relationship probably to certain rather 

 poorly known Asiatic genera. 



The subfamily Heteronemiinae is entirely one of Neogaea, with 

 representatives distributed from Canada to at least Paraguay. 

 Five genera have been reported from western North America, and 

 all but one of these I would regard as of Sonoran development. 

 The exception is Sermyle, which is clearly a Mexican and Central 

 American Neotropical type, with a single species found in southern 

 Texas. Of the other four genera, Megaphasma is an endemic usually 

 infrequent in forest, generally bottom, land of eastern Texas, Okla- 

 homa, Louisiana, and other Mississippi valley areas, but narrowly 

 entering the territory we are considering. Two of the three remain- 

 ing genera, Rhabdoceratiies and Psendo sermyle, are limited to west- 

 ern North America, except for narrowly reaching into Sonoran 

 sections of Mexico. They doubtless have developed in the great 

 Sonoran area, where Pseiidosermyle in particular is a dominant 

 type. The remaining genus, Diapheromera, is probably also a Sonoran 

 derivative, for several of its species are limited to that area. One 

 species of the genus, however, has spread more broadly eastward 

 over most of eastern North America, and there also has developed a 

 very distinctive species in the southern Appalachians. The south- 

 eastern and central United States apparently have served as a 

 secondary developmental center for the Heteronemiinae, not only 

 for Diapheromera, but also in producing there an endemic genus 



