194 The Sugar-Beet in America 
and attack sugar-beets only incidentally. Grasshopper 
injury varies greatly from year to year, usually increasing 
gradually up to a climax year and then dropping off sud- 
denly to begin the gradual ascension again. At least a 
dozen species are known to attack sugar-beets. 
Grasshoppers are commonly kept within normal num- 
bers by natural enemies, among which are birds, fungous 
diseases, and other insects. Mechanical means of coping 
with them, such as that shown in Plate XXI, are also used. 
Plowing under the eggs before they have had time to 
hatch is probably the most effective means of controlling 
them when the breeding grounds can be handled in this 
way. Several types of catchers are also used with success. 
Arsenic-bran mash is the most economical and effective 
poison. 
Beet-root aphis (Pemphigus betae Doane). 
Within the last few years the beet-root aphis has spread 
rapidly over the beet-growing sections of the United 
States. Attention was first called to it in 1896. It is 
similar in appearance to its relative, the woolly aphis of 
the apple. The insect lives on the small roots of the beet, 
sucking juice from it and thereby dwarfing the plant. It 
protects itself by means of its woolly covering and is 
consequently not injured by irrigation water. At inter- 
vals a generation of winged individuals appears; these 
fly to other fields, where they settle down and begin a 
new colony. In the fall, winged females fly to cotton- 
woods and lay eggs on the trunks. These hatch in the 
spring and migrate to leaves, where they pass one or more 
generations before going to the beet fields. In Colorado, 
