Corn Earworm as an Enemy of Vetch. 9 
lapping of the generations makes it possible to find all stages of the 
insect at any time during the summer and fall months. 
LIFE CYCLE. 
The corn earworm in its life history passes through four distinct 
stages: First, the egg (fig. 5); second, the larva or caterpillar (fig. 
6); third, the pupa or resting stage (figs. 7 and 8); and, finally, 
the moth or mature insect (figs. 2 and 9). 
THE EGG. 
The egg (fig. 5) of thevcorn earworm moth is hemispherical in out- 
line and somewhat smaller than a pinhead. It is a uniform light 
yellow when just de- 
posited, but towards 
the end of the incuba- 
tion period it becomes 
mottled with reddish 
brown. The duration 
of the incubation pe- 
riod varies from 3 
days in summer to 
from 5 to 8 days in 
early spring or late 
fall. There is also a 
great variation in the 
Fic. 6.—Three corn earworm lary, seen from the side, 
number of eggs de- showing color types: Upper larva, green; middle one, 
posited. A moth de- rose colored; lower one, dark brown. Twice natural 
size. (Quaintance and Brues.) 
posits on an average 
about 800 eggs during her lifetime and about 300 during an evening. 
She may deposit as many as 500 eggs in one evening, however, and 
over 2,500 during her lifetime. The eggs are deposited singly, just 
before dusk, on various parts of plants upon which the caterpillars 
feed. 
THE LARVA OR CATERPILLAR. 
The caterpillar or larva (fig. 6) is the stage in which the insect 
attacks and destroys the plant. The newly-hatched caterpillar is 
pale yellowish white with a pitch-black head. It walks with a loop- 
ing motion somewhat similar to that of a “measuring worm.” This 
is due to the second and third pairs of legs being shorter than the 
first in the young larve. In the full-grown individuals they are 
all equal in length. 
The body of the caterpillar is covered with numerous wartlike 
humps of a dark color, each one of which bears a short hair. These 
39672°—21—Bull. 1206 
9 
