210 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



water to make a moist, crumbly mash. Aldrin dusts or sprays are 

 highly effective. 



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 dragging a log over them. Fortunately 

 armyworm invasions on forest ranges are not of very frequent 

 occurrence. 



The Great Basin tent caterpillar (Malacosoma fragilis Stretch) 

 (figs. 37, 101) (see p. 95) appears from time to time in the 

 Great Basin area between the Rocky Mountains and the Cascades 

 and defoliates 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 bitterbrush that it took several seasons for it to recover, and 

 the carrying capacity of the ranges was greatly reduced. Epi- 

 demics could probably be controlled by aerial applications of DDT 

 in fuel oil, provided a cost of $1 per acre is justified. After a few 

 seasons of heavy feeding, often with serious injury to the older 

 plants, outbreaks are brought under control by natural enemies. 



The range caterpillar (Hemileuca oliviae Ckll.) (160) 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 Mexico. The adults are large moths with reddish, brown, or 

 black bodies and buff or clay-colored wings. The caterpillars are 

 yellow, gray, or black and have numerous coarse, poisonous spines. 



The California tortoise-shell butterfly (Xijmphalis calif ornica 

 (Bdv.) (fig. 102) is found throughout all the Western States and 

 often appears in such numbers as to attract public attention. 

 The caterpillars feed on different species of Ceanotkus, and dur- 

 ing severe epidemics other shrubs and trees may be attacked. 

 The adults are medium-sized butterflies with a wing expanse of 

 2 to 2 L 4 inches. The wings are brown, with orange above, marked 

 with black spots and black borders, with a single black spot and 

 a marginal row of purple spots on the hind wings. The caterpillars 

 are 1 to l 1 ^ inches in length, black with fine-branched spines on 

 each segment, the middle row being bright yellow. The adults 

 are in flight during midsummer. 



The peppergrass beetle (Galeruca externa Say) is a black oval 

 beetle about y 4 inch long, with a narrow yellow border on the 

 elytra, which feeds on lupine in the Great Basin area. In 1934 it 

 destroyed the lupines over hundreds of acres in eastern Oregon 

 and also fed on the grasses. 



The range crane fly (Tipula simplex Doane) (128) at intervals 

 is very destructive to grasslands in California. It is also a serious 

 pest of grains, barley, and alfalfa. The adults are grayish brown, 

 long-legged flies about y 2 to % inch long. The females are wing- 

 less. The larvae, which are pale brown and somewhat roughened, 



