20 FURTHER RESEARCHES ON NORTH AMERICAN ACRIDIID^. 



The eastern part of the Territory and northeast Texas are similar 

 in topography, habitats, and fauna to western Arkansas, and the same 

 species are met with under the same conditions. As one proceeds 

 west from Arkansas through the Territory and Oklahoma, or through 

 Texas, a decrease takes place in the number of eastern, hygrophilous 

 and sylvan species met with, and at the same time a much greater 

 increase occurs in the number of species characteristic of the prairies 

 and plains, xerophile and campestrian in habits and Sonoran in affini- 

 ties. This may be seen at Caddo and Denison by comparison of the 

 fauna of the wooded strips and of the prairies near these localities. 



Among the earliest species to diminish in number and disappear 

 are Dichromorpha viridis, Orphulella pelidna, Spharagemon bolli, Mela- 

 noplus robustus and keeleri. Among those that appear earliest in travel- 

 ing westward in addition to those already mentioned as occurring in 

 Arkansas are Phoetaliotes nebrascensis and Melanoplus plebejus in moist, 

 grassy field-thickets ; Arphia luteola and simplex, and Encoptolophus 

 patvus in drier fields ; Ageneotettix deorum and Hadrotettix trifasciatus 

 on bare, stony, or sandy areas; Hypochlora alba occurs locally on white 

 sage (Artemisia spp. ; pi. i, fig. i) ; Opeia obscura lurks in the dense 

 cover of the mesquite grass, together with increasing numbers of 

 Trachyrhachis fuscifrons and Orphulella picturata ; Mermiria neo- 

 mexicana appears and with bivittatus inhabits the taller bunch-grasses 

 {Andropogon, Chr^sopogon, etc.). Especially characteristic of loose 

 sand, such as occurs at Bonita, in the Upper Cross Timbers, and 

 locally everywhere, are Spharagemon cristatum and Psinidia fenestralis. 



The locust fauna of the dry prairies and lower plains, the ' ' prairie- 

 plains ' ' or semi-arid portion of the Texas region , was studied at 

 Wichita Falls, Quanah, and Clarendon, Texas, and Mountain Park 

 and Cache, Oklahoma. The list of species taken at these localities 

 between August 15 and 25 is as follows: 



Paratettix cucullatus. Boopedon nubilum. 



Mermiria bivittata. Arphia xanthoptera. 



Mermiria neo-mexicana. Arphia nietana. 



Syrbula admirabilis. Arphia luteola. 



Eritettix sp. Chortophaga viridifasciata. 



Opeia obscura. Encoptolophus costalis. 



Amphitornus bicolor. Encoptolophus parvus. 



Phlibostroma quadrimaculatum. Hippiscus corallipes. 



Orphulella decora. Hippiscus immaculatus. 



Orphulella picturata. Hippiscus rugosus. 



Ageneotettix deorum. Hippiscus saussurei. 



Aulocara elliotti. Leprus wheeleri. 



Aulocara femoratum. Dissosteira Carolina. 



