268 J. A. G. REHN 



ably true of the array of distinctive genera found broadly over 

 areas of central and western Texas {Phaedrotettix, Phaiilotettix, 

 Paratdemona, Chloroplus, and Agroecotettix). The genus Aeoloplides 

 is of broad distribution in the Great Plains, the Sonoran deserts of 

 the southwestern United States, the Great Basin, and areas of 

 California, and is probably a relatively old line, very adaptable to 

 the distinctly thamnicolous habitat it prefers. The genus Aidemona 

 is narrowly present in our territory as an intrusive from Mexico and 

 Central America (it ranges southward to Colombia). 



In the Sonoran desert mountains and on the benches of the south- 

 western United States we find a group of genera that probably 

 originated there, or in adjacent northern Mexico, where they also 

 do or may occur. These are Conalcaea, Barytettix, Poecilotettix, 

 and Aztecacris. Another clearly Sonoran type is the genus Hes- 

 perotettix, which is of wide distribution over most of the lower level 

 land areas of the western United States and Canada, where its 

 favorite cover of yellow-flowered composites of several genera 

 ("rabbit weed") occurs. Two lines of the genus undoubtedly entered 

 the southeastern United States from more western territory a 

 considerable period in the past and there developed a subsidiary 

 evolutionary center of the genus, while another line of campestran 

 relationship spread in ecologically suitable areas over much of the 

 eastern states. In many areas of California and of the Great Basin, 

 as well as the Columbia River and Snake River plains, the genus 

 Oedaleonotus has developed a marked radiative speclation. It 

 apparently is an autochthon which has no very close relatives. 



In mountain areas of the western United States and southwestern 

 Canada there have developed a number of apterous, and of course 

 flightless, endemic genera, of which three, Bradynotes, Prumnacris 

 and Buckellacris, are of Canadian and Hudsonian Zone distribution. 

 The most highly specialized is probably Brady?iotes, which occurs in 

 isolated areas of the more northern Rockies in the United States 

 and adjacent Canada, the Cascades, the pumice plains east of the 

 Cascades in Oregon, and in the more northern Sierras. The genus 

 also reaches southward to the Kaibab Plateau of northern Arizona, 

 although in the main Rockies it is not known from south of South 

 Pass, Wyoming. It is possible future work may show that Prumn- 

 acris and Buckellacris, as well as the strange Nisquallia of the 

 Olympic Mountains of Washington, are more nearly related to 



