DERMAPTERA AND ORTHOPTERA 297 



family in North America and in Mexico. The North American 

 species represent two quite distinct genera, one of which, Arenivaga, 

 is now considered by Russian colleagues also to include certain 

 Central Asian species. Of Arenivaga seven species are now recognized 

 in North America, all but one of which are found within the territory 

 covered by this symposium. Several also occur in northern Mexico. 

 The one exception is known only from Florida, but it clearly has 

 been derived from the Sonoran area where the other species have 

 developed. The forms of Arenivaga in our territory range from 

 east-central Texas west to southern California, and north as far as 

 Monterey, California, St. George, Utah, and Oklahoma. The other 

 genus Eremoblatta, is more exclusively a desert type. Its distribution 

 extends from eastern New Mexico and extreme western Texas to 

 the Mohave and Colorado deserts of California, north to Kern 

 County, California, and to Las Vegas. Nevada. 



The last genus of the Blattodea to be considered is in some 

 respects one of the most interesting of our North American blattids. 

 This one, Cryptocercus, is the sole member of the subfamily Panes- 

 thiinae in the New World. Like many of the other species of the 

 subfamily it lives in dead wood, can digest cellulose, bores channels 

 in dead logs, preferably of fir or chestnut, and is also wingless. In 

 North America the genus, and its single American species, is dis- 

 continuously distributed. It is found in the eastern Appalachians 

 and the Appalachian Plateau from New York to Kentucky and 

 Georgia, and again is present in western Washington, the Cascades 

 of Oregon, and possibly the Sierras of California. It is absent from 

 virtually all the Middle West, the Great Plains, the Rockies, and 

 the intervening basins, even where these are heavily timbered. 

 Apparently the separation of the two distinct areas of the distribu- 

 tion of the species has been due to the southward advance of the 

 lobes of the various Glacial ice sheets, which severed previously 

 connected areas and isolated the two elements of the species, in the 

 same way the two segments of the acridoid genus Zubovskya were 

 developed (but in that case specific entities were established). 

 The particularly interesting feature in connection with Crypto- 

 cercus is that it, with several distinct species, also occurs in eastern 

 Asia. Clearly we have here a case basically parallel to those of the 

 acridid Zubovskya and the decticid Atlanticus, although the ex- 

 planations for each may not be identical, but in their patterns they 



