FURTHER RESEARCHES ON NORTH AMERICAN ACRIDIIM. 7 



LIFE ZONES OF REGION EXAMINED. 



The region examined lies entirely within the Austral life zones, 

 between the parallels of 29 20' and 36 10'. The highest mountain 

 summits visited Cheaha Mountain, Alabama, 2,400 feet; Magazine 

 Mountain, Arkansas, 2,800 feet; Mount Sheridan, Oklahoma, 2,500 

 feet, and the Great Plains at Amarillo, Texas, 3,600 feet do not 

 reach an altitude sufficiently high to provide boreal conditions, but 

 show traces of a Transition element. The Upper Austral zone was 

 studied on the highlands of northeastern Alabama, western Arkansas, 

 the Wichita Mountains of Oklahoma, and at Amarillo. The Gulf strip 

 of the Lower Austral was touched at three points in southern Missis- 

 sippi and the same number in Louisiana. 



Wichita Falls, Texas; Cache, Oklahoma, and localities west of 

 those points lie in the arid or Sonoran division of the Austral zones. 

 This section is, however, more strictly semi-arid than arid in charac- 

 ter, when compared with the extreme arid region of southwest Texas, 

 New Mexico, Arizona, etc. 



At present it is impossible to state with certainty which species 

 are characteristic of each of these zones and districts. 



HUMID AND ARID FAUNAS, DISPERSAL, BRACHYPTERISM. 



Two of the chief biological points upon which it was desired to 

 secure information in the region visited were in reference to the status 

 of brachypterous species in treeless districts,. and the transition be- 

 tween the faunas of the humid and arid parts of the Austral zones. 

 Based upon the data secured on this trip, it would appear that as a 

 whole the biota of the treeless plains and prairies is characterized by 

 an Acridian fauna richer in number of species than that of the East, 

 and that these are of geophilous and campestrian character in conso- 

 nance with the climate and the habitats represented. While differing 

 much in general facies from that of the Eastern States of the same 

 latitude in these particulars, the transition from humid to arid con- 

 ditions and fauna is gradual rather than abrupt,* the borderland of 

 the two in Texas, Indian Territory, and Oklahoma being peopled by 

 numerous genera and species of very wide, in some cases transconti- 

 nental, distribution, and also by some of more limited range restricted 

 to the district between the Mississippi River and the Rocky Mountains, 

 but occurring both in the humid and arid sections of this region. 



Dispersal of the xerophile, arid-land species is doubtless chiefly 

 effected through the agency of the winds, especially the strong south - 



*Possibly this conclusion may need qualification after more detailed study. 



