188 The Sugar-Beet in America 
periods. Outbreaks of this pest in the beet fields of the 
western states have at times nearly ruined the crop. With 
the exhaustion of its usual food in years when it is worst, it 
migrates from field to field devouring everything in its 
course as shown in Plate XXI. The larvae which do the 
injury are naked, dull-striped worms resembling cutworms 
and closely related to them. Except when moving in 
armies, the worm is not noticed, because it usually remains 
concealed in the daytime, feeding mainly at night. When 
full grown, the worm is about one and one-half inches 
long, of a dark color except for a yellowish stripe down the 
back and one down each side. The second brood makes 
its appearance in the latter part of the summer; as a 
result, late plantings suffer most. Its normal food plants 
are certain weeds; hence clean culture will prevent a 
number of the pests from developing. Poisoning with 
paris green or arsenate of lead offers much relief when 
there are a great number of the insects. The poison should 
be applied as soon as injury is noticed. 
The common army-worm (Leucania unipuncta Haw). 
This species is similar to the above except that it has 
three yellow stripes instead of one down its back and it 
winters as a half-grown larva in the ground, emerging in 
the spring as a dull brownish moth. It more often at- 
tacks cereals and grasses, but also eats sugar-beets. This 
worm does its injury in early summer, whereas the beet 
army-worm is most troublesome in late summer. This 
insect troubles more crops than the beet army-worm and 
is more widely distributed. Ordinarily, it is held in check 
by its natural enemies, but when it becomes excessively 
