DERMAPTERA AND ORTHOPTERA 285 



of species in North America south only to northern Mexico, and 

 they are considered to have had as their main centers of differentia- 

 tion (a) the Eastern Deciduous Forest, {b) the Sonoran region, and 

 (c) the northern Great Basin. In the more arid regions of western 

 North America specific Hnes of Ceuthophilus appear Hmited to 

 mountain areas, probably as hot lower levels are less favorable for 

 their existence. It is very probably that the tribe had a broader and 

 less localized range in western North America in the moister and 

 cooler Pleistocene, and that present distributional patterns, as for 

 many other groups, reflect an average greater aridity in Recent 

 times. 



Superfaniily Gryllodea 



The second superfamily of the existing suborder Ensifera, the 

 Gryllodea, has, in a conservative evaluation of its component 

 major groups, three families in our fauna, the Gryllotalpidae, or 

 mole crickets, the Tridactylidae, or pygmy crickets, and the 

 Gryllidae, to which belong the true crickets. 



The oldest fossil of an undoubted mole cricket, from the Upper 

 Miocene of Germany, is considered to represent an existing genus, 

 Gryllotalpa, and to be closely related to the existing European 

 G. gryllotalpa. Zeuner believes that both the Gryllotalpidae and the 

 Gryllidae have developed independently from the Liassic Proto- 

 gryllinae, and that the Gryllotalpidae have not evolved through 

 the medium of the Gryllidae. In western North America we find 

 but one genus of the Gryllotalpidae, which is variously referred to 

 as generically identical with Gryllotalpa of the Old World, or 

 representative of a New World genus Neocurtilla. It is clearly evi- 

 dent, however, that the two distinct species of this genus in North 

 America are of Neotropical derivation, as one, found broadly over 

 the United States west to the Rockies, is also widely spread over 

 eastern South America, and the other, the sole species occurring 

 very locally and infrequently from Texas to California, is closely 

 related. 



The position of the Tridactylidae, or pygmy locusts, which were 

 long considered gryllids, is now regarded broadly as with the 

 acridids. I mention the group here, as this is the position given in 

 most past literature. Their ancestral stock is now known from the 

 Tertiary, but the single genus found broadly in North America 



