300 I? E PORT UNITED STATES ENTOMOLOGICAL COMMISSION. 
with stunted sage, or are barren. It is unnecessary to go into details 
regarding them, as the accompanying map expresses them better than 
any description could do it. 
There is ;i plainly marked gradation southward in the vegetation. 
Of the Mojave I >esei t, of Southeastern < 'alifornia, Little Deed be said, 
save that it is almost without vegetation, excepting at a few isolated 
spots, where springs break through to the surface, forming small oases, 
and the narrow belt along the Mojave River. On the borders of the 
San Bernardino Range, however, there is a narrow belt of grass, while 
the higher portion oft he range is well timbered. 
PREVENTIVE MEASURES IN THE PLAINS AREA. 
From the foregoing account of the topographical and botanical char- 
acteristics of the different areas in the Permanent Region, taken in con- 
nection with what we have said both in this and our previous report, it 
is obvious that the plains area transcends in importance all the other 
areas here considered, from the locust point of view. 
The surface conditions under which Caloptenus upretus breeds in the 
greatest abundance are a loose, warm, gravelly soil covered by a tolerably 
luxuriant growth of grasses, such as are found in most river bottoms; 
in the northern part of the plains of British America, along the bases of 
the mountain ranges, and in the high mountain valleys. Such areas are 
of greater extent in the northern portion of the region which we have 
described, becoming very much more limited in the Southern States and 
Territories. 
While it is quite possible that the insects may breed anywhere on the 
plains, it is certain that, as shown in our first report, the more fertile 
portions of this area, and especially that great fertile belt between the 
two Saskatchewan, in British America, is the principal source of the 
swarms which at times sweep down upon the prairies. The extent of 
these breeding grounds in British America may be approximately esti- 
mated at about 100,000 square miles. 
In Montana there is a broad belt at the eastern base of the Missouri 
Range, extending down the branches of the Missouri River for long 
distances. The country about Sun and Teton Rivers is very luxuriant, 
even as far as their mouths. The Gallatin Valley is luxuriantly grassed. 
The lower slopes of the Judith and other neighboring groups of mount- 
ains, the country about the base of the Yellowstone Range, the valleys 
of the Jefferson and its branches, with the hills in their neighborhood, 
may also be looked upon as breeding places of the pest. On the west- 
ern or Pacific Slope, the valleys of the Deer Lodge, Bitterroot, and Hell- 
gate, and of several of their branches, fall into the same category, as 
also the valleys of the Kootenai, and of Flathead Lake. 
The bottom lauds of many of the streams of the plains, though com- 
paratively narrow, afford probable breeding grounds. Those of the 
Missouri are quite narrow, but on the Yellowstone they have an average 
