164 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 
INSECTS INJURIOUS TO FOREST RANGE PLANTS 
Grasses, herbage, and browse, which furnish feed to range ani- 
mals, comprise a forest product sometimes of greater economic 
importance or value than the trees that grow on the area. These 
grazing plants may also suffer from insect attack and at times 
are so completely destroyed in certain localities that cattle and 
sheep have to be moved to other ranges. Moreover, the damage 
to browse plants may carry over from year to year and reduce the 
available feed for several years. Fortunately there are compara- 
tively few insects that cause serious damage to range plants. 
The damage which grasshoppers may ‘do to the erazing areas 
is well known to everyone, and the insects themselves are such 
common pests as to require no description. They are often par- 
ticularly abundant in grassy meadows, where the females lay their 
egos in the ground. usually during the fall of Me year, and new 
broods emerge each spring to feed on all kinds of green and dry 
vegetable matter. The nonmigratory grasshoppers remain in a given 
locality and produce a new brood each year, under favorable con- 
ditions becoming excessively abundant and destructive. Others are 
migratory in habit and, after breeding to enormous numbers, and 
having developed ene travel across the country devouring every 
growing thing in their path. 
Much attention has been given to the control of grasshoppers, 
and effective methods have been devised, the most satisfactory con- 
sisting in spreading poisoned baits broadcast over the breeding 
areas at about the time the young hoppers first come out and begin 
feeding. A good bait consists of a mixture of 1 pound | of white 
arsenic, sodium arsenite, or paris green to 25 pounds of bran or 
middlings, 2 quarts of blackstrap, and enough water to make a 
thin mash. 
Periodically armyworms, which are caterpillars of certain noctuid 
moths, appear in countless numbers and advance over grazing areas, 
devouring everything in their path. These also can be controlled 
to some extent by the application of poisoned baits similar to those 
used for grasshoppers, or by plowing trenches in front of the 
traveling army of worms and ‘killing them in the trenches by drag- 
ging a log over them. Fortunately armyworm invasions on forest 
ranges are not of very frequent occurrence. 
The Great Basin tent caterpillar (Malacosoma fragilis Stretch) 
appears from time to time in the Great Basin area between the Rocky 
Mountains and the Cascades and defoliates the bitterbrush (Purshia 
tridentata), which is a most important browse plant for sheep in this 
area. From 1928 to 1930 an invasion of this caterpillar swept over 
the range country of eastern Oregon and northern California and so 
seriously damaged the bitterbr ush that it took several seasons for it 
to recover, and the carrying capacity of the ranges was greatly 
reduced. No practical control for this pest has been suggested, but 
fortunately outbreaks are brought under control by natural enemies 
after a few seasons of heavy feeding. 
The range caterpillar (Hemileuca oliviae Cxkll.) (86) feeds on 
wild grasses and sometimes on cultivated crops, and at intervals of 10 
or 12 years is a serious range pest from Colorado southward into 
