286 J. A. G. REHN 



is the almost cosmopolitan Tridactyliis, one of the very few genera 

 of these strangely specialized orthopterons. 



Passing to the true Gryllidae, of which a number of subfamilies 

 are generally recognized, the Myrmecophilinae, composed of ant 

 inquilines, is represented in our fauna by the single widely spread 

 genus Myrmecophila. While members of the genus occur in certain 

 tropical countries, most of our knowledge of the group has been 

 drawn from representatives found in more temperate regions. At 

 least four species occur in western North America. No fossil forms 

 are known and any postulate as to centers of origin seems at present 

 unwarranted. 



The subfamily Mogoplistinae, of which also no fossil forms are 

 known, is represented in western North America by two genera, one 

 of which, Cydoptiliim, is distributed broadly over the southeastern 

 United States, narrowly enters the Campestran region, extends 

 from Texas to coastal southern California, and is intrusive in the 

 Colorado- Virgin rivers area to southeastern Utah. Cydoptiliim is 

 broadly distributed in tropical regions, even occurring in Polynesian 

 islands, but it apparently developed certain centers of evolution or 

 radiation, where a number of distinct species occur, one in the south- 

 eastern United States, and another in its southwestern section, 

 Baja California and apparently extreme northern Mexico. The 

 second genus, Hoplosphyrum, is peculiar to the Sonoran region of 

 North America, Baja California, and mainland Mexico, with one 

 species in each of these areas, but it does not, as far as we know, 

 extend greatly to the southward. 



The single genus of the subfamily Nemobiinae in western North 

 America is virtually cosmopolitan in distribution. The subfamily 

 is known fossil only from the Oligocene, in Prussian amber and 

 Isle of Wight deposits. The dominant and widely distributed genus 

 Nemobius clearly developed an evolutionary center in the eastern 

 and central United States, where a number of endemic species occur. 

 Six species and subspecies of the genus occur in western North 

 America which the genus appears to have entered by this group 

 from both Mexico and the eastern United States. Several species 

 are but narrowly present in the southwestern United States. Another 

 is a Campestran subspecies of an eastern species and reaches the 

 foot of the Rockies in eastern Colorado. Of two subspecies of a dom- 

 inant and widely spread eastern species, N. fasciatus, one reaches 



