296 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION 
ber extends westward over the plateau to its edge and down the slopes. 
The whole edge of the plateau is covered with forests from the mount- 
ains in New Mexico westward and northward nearly to the Colorado. 
This timber belt is accompanied on its northern side by a strip of vary- 
ing width of pasture land, extending in some places nearly to the Colo- 
rado ( 'lliqllito. 
From the edge of the plateau, the country falls rapidly towards the 
Gila and the deserts of Lower Arizona. About the heads of the Gila 
there are many groups of mountains, most of which are timbered, while 
the valleys and plains are well grassed. All along the slope of the Colorado 
Plateau the country is broken, timber occupying most of the mountains, 
while the valleys are grassy. As the elevation diminishes, the vegeta- 
tion changes and decreases, and when we reach the lower levels, we 
meet with the system of narrow, parallel ranges and valleys, most of 
the former being grass-covered, or possibly crowned with a few scatter- 
ing trees, the latter mainly barren. Of this description is the country 
along the Lower Gila, and it.- branches, the Colorado and Williams Fork. 
The country along the Mexican boundary in Arizona is nearly all of this 
description, though improving to some extent from the longitude of 
Tucson eastward. 
The Great Basin Area and the Wasatch Mountains. 
This region, which finds no outlet save evaporation, comprises por- 
tions of the following States and Territories : Oregou, Nevada, Utah, 
and California — itself one great basin, it comprises a number of smaller 
ones, which may be classified comprehensively into three, namely : that 
of Harvey's Lake, Oregon ; of Salt Lake, Utah, and of Carson-Hum- 
boldt Lakes, Nevada. 
The characteristic surface feature is that of narrow, parallel ranges, 
trending nearly north and south, separated by narrow, partly-filled val- 
leys. 
The most fertile regions of the basin are among the ranges in the 
drainage area of tributaries to Great Salt Lake, in Utah, and in the north- 
ern parts of Utah and Nevada. 
Proceeding now to the drainage area of Bear River, one of the larges 
tributaries of Great Salt Lake, we find that its valleys, with the single 
exception of the upper one of all, that which extends from the base of the 
Uinta Mountains down to the mouth of Smith's Fork, can easily be burned 
over ; that the ranges of hills and low mountains which separate these 
valleys are grass-covered, while the higher ranges, such as the Bear 
River and Wasatch Ranges, are covered with a somewhat sparse growt 
of timber. 
The upper valley of the Bear, extending, as was said above, from the 
base of the Uinta Range northward to the mouth of Smith's Fork, with 
a few minor interruptions, is clothed only with a sparse growth of 
