6 FARMERS’ BULLETIN 1752. 
and a fresh outbreak begins, and the female moths developing from 
the larve again fly northward before depositing their eggs. In this 
manner the fall army worm during favorable summers manages to 
spread over the entire eastern portion of the United States, even 
reaching southern Canada before the severe frosts of autumn inter- 
vene and halt its northward flight. 
WHEN INVASIONS MAY BE EXPECTED. 
General invasions of the fall army worm occur almost invariably 
following cold, wet springs. In some parts of the Mississippi Val- 
ley the pest is known as the 
“overflow worm,” since the 
farmers attribute outbreaks 
of the insect directly to the 
overflowing of the great 
river, and it should be stated 
that there is evidence which 
appears to support this be- 
hef. The effects of cold and 
dampness on the insect ene- 
mies that ordinarily control 
the fall army worm are ap- 
parently disastrous, while 
such conditions have little 
or no ill effect on the 
ce ailill caterpillars of the pest. It 
| may be for this reason 
a that local outbreaks occur 
VAN iil nearly every year in the 
Fie. 3.—Eggs of the fall army worm: Egg mass South in scattered localities 
at left about twice natural size; a, highly mag- gfter periods of heavy, lo- 
nified egg, side view ; 0b, same, view from above ; . 5 . 
c, greatly enlarged egg about ready to hatch, calized rainfall and humid 
larva showing through the shell. (Original.) weather. 
LIFE HISTORY. 
The fall army worm, in common with many other insects, passes 
through four stages in its development: First, the egg; then the 
larva, or caterpillar, which is the stage of growth and injury to 
crops; then the pupa, or resting stage; and, finally, the stage of the 
moth, or mature insect. 
THE EGG STAGE. 
The eggs (fig. 3) are laid by the moths at night in clusters of 
from 50 to several hundreds, preferably on grass blades. Low-lying 
fields thickly covered with grass or small grains are often chosen 
{ 
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