280 J. A. G. REHN 



North America occur west of the Continental Divide. Two of the 

 three subgenera of Conocephalus known from North America are 

 almost entirely confined to the eastern and central parts of the 

 continent. We doubtless received the ancestral stock of these lines 

 from the Neotropical Region well before the Pleistocene, and they 

 probably evolved almost entirely in the southeastern United States 

 between their advent there and the present. It is also quite probable 

 that the two forms of the genus peculiar to the western United 

 States have evolved from eastern species, while the other two there 

 present are relatively localized western extensions of broadly 

 dominant eastern species. 



Until very recently the subfamily Listroscelinae was not con- 

 sidered to be present in North America or even in Mexico. Recent 

 work has shown that the genus Rehnia, which occurs from Kansas 

 to the Rio Grande and southward into northern Mexico, and there 

 westward to Sinaloa, is a member of the Listroscelinae, a subfamily 

 chiefly of pantropical distribution, with a number of most distinc- 

 tive genera in South America. Apparently Rehnia is a bush- and 

 tree-loving Sonoran development from a line of the subfamily, 

 the entry of which into our general region from a Neotropical stem 

 probably dates back a considerable time. Another genus of the 

 same subfamily Neobarrettia is an inhabitant of the very hot Rio 

 Balsas Valley of Guerrero, Mexico, while the remainder of the 

 Neogaeic genera of the subfamily occur almost exclusively in South 

 America and more southern Central America. 



The subfamily Decticinae is made up of a very extensive array of 

 genera occurring almost entirely in the Nearctic and Palearctic re- 

 gions. A very few narrowly extend southward and several isolated 

 genera are known from South America. A large percentage of the 

 members of the subfamily are bush- or thicket-loving species, 

 but some are grassland types, and others live entirely on the ground 

 in forested areas; a very few, such as the Mormon cricket {Anabrus) 

 and the coulee cricket (Peranabrus) are often economic problems, 

 and these latter, although flightless, have well-developed migratory 

 instincts when in search of food. In North America only one genus 

 {Atlanticus) is limited to its eastern part, while twenty-one genera 

 are known from, and all but one are peculiar to, the western part of 

 our continent. One interesting peculiarity is that the one eastern 

 genus, Atlanticus, is the only one having its greatest diversity in 



