4 Farmers’ Bulletin 1140. 
Immense swarms of grasshoppers are sometimes held on the uncul- 
tivated lands because of the presence of certain weeds which are 
natural food plants. Cutting meadow grasses or alfalfa on severely 
infested fields may cause the grasshoppers to migrate to other fields 
or orchards. A hot wind may cause sudden migration, while cool, 
dark weather frequently results in considerable inactivity on the 
part of these pests. 
FAVORABLE AND UNFAVORABLE CONDITIONS. 
Dry weather favors the development of young grasshoppers, pro- 
vided they have the necessary green food, and the most severe out- 
breaks follow a succession of compara- 
deposit their eggs on knolls, ridges, or 
well-drained hillsides. In the Sacra- 
mento Valley of California grasshoppers 
also hatch in large numbers on grass 
lands which sometimes are flooded by a 
foot or more of water in early spring. 
A similar condition obtains in some of 
the valleys of the Sierra Nevada Moun- 
tains, where the meadows are flooded 
and thawing, or even severe drying after 
an early fall rain, appears to disturb 
many of the egg pods sufiiciently to admit 
moisture and destroy the eggs. A heavy 
frost is fatal to many nymphs. Cloudy 
weather and cool rains are conditions un- 
favorable to their development. 
SOME OF THE COMMON DE- 
STRUCTIVE GRASSHOPPERS. 
ic. 1.—The Gaimorns devastating The California devastating grasshop- 
Saunt ae per’ (fig. 1) is yellowish brown in color, 
and has small dark spots on the wings. 
It measures about 1 inch in length. It breeds mostly on dry lands and 
dry alfalfa fields. The adults of this species are active in flight, and 
are very destructive to orchards, vineyards, alfalfa, gardens, and bean 
fields. 
The differential grasshopper ? (fig. 2) is a large species, measuring 
about 14 inches in length. In color it varies from yellow to rich 
1 Melanoplus devastator Scudder. 2 Melanoplus differentialis Thomas. 
tively dry years. Grasshoppers usually - 
after the snows melt. Alternate freezing . 
1 a a. ee eee ae oe 
