DERMAPTERA AND ORTHOPTERA 275 



border, on arid rocky hills and in brush land, while another, definite- 

 ly a Campestran (Great Plains) type, narrowly extends into Mexico. 

 Pseudopomala, a near relative of Mermiria, is widely distributed 

 over the more northern section of the United States, occurring 

 sparingly in restricted environments. At least some of its present 

 spotty distribution probably can be explained as a subsequent 

 readjustment to Glacial displacement, but on this point more 

 study is needed. 



The highly specialized genus Radinotatum is largely limited to 

 the southeastern United States, but includes a quite distinct species 

 in southern Texas. Its nearest relative is apparently Achurutn, 

 which is Mexican in origin, although found within our limits in 

 southern Arizona. The genus Prorocorypha is of localized occurrence 

 in certain mountains of extreme southern Arizona. Its nearest rela- 

 tive is the rather broadly distributed and highly specialized, equally 

 graminicolous Sonoran genus Paropomala. The genera Acantherus 

 and Horesidotes are apparently endemic generic types of the Sonoran 

 Mexican border country in Texas, New Mexico, Arizona, and 

 California. The same is true of the strictly thamnophilous genera 

 Ligurotettix and Goniatron, the former of which does not occur east 

 of the Continental Divide and extends northward as far as west- 

 central Nevada, while Goniatron lives almost entirely east of the 

 Continental Divide in the Chihuahuan Desert area and is much 

 more limited in its north and south distribution, but with its range 

 definitely known to extend a considerable distance into northern 

 Mexico. In habitat Goniatron is restricted to "black brush" (Flour- 

 ensia), while Ligurotettix is found on more than one species of 

 shrub, but often on creosote bush (Covillea). 



The genus Pedioscirtetes comprises two lines of development, one 

 of which occurs in the Mexican border territory from western 

 Texas to southern Arizona, as well as some distance southward into 

 Mexico; the other is known only from very limited, distinctly more 

 elevated areas in northern Arizona, Nevada, Utah, and southern 

 Idaho. It appears to me that the genus originally developed in our 

 older plateau areas adjacent to the Cordilleran mass, and that one 

 element moved southward, perhaps in Pleistocene times, while the 

 other remained, survived lower temperatures, and has even extended 

 its range northward. The genus Bootettix is always associated with 

 the Lower Sonoran creosote bush {Covillea), and is almost never 



