~Webworms Injurious to Cereal and Forage Crops. 7 
grow larger they are soon able to eat the entire leaf, and when they 
become too large to be concealed within the fold of a leaf, descend 
and construct in the earth a burrow lined with silk, with an opening 
at the surface and sometimes continued upward along the grass stem 
in the form of a tube 
made of silk and bits 
of grass. From this 
time on the worms 
cut off the blades of 
grass entirely and 
drag them down into 
the burrow, where 
they feed in safety 
and at leisure. Often 
one finds a blade of 
grass projecting from 
the entrance of such 
a burrow while its 
motion and gradual disappearance indicate that down below the busy 
harvester is turning grass into worm as fast as possible. 
In order to allow for its rapidly increasing size the larva molts 
or sheds its skin several times until it reaches a length of half an inch 
or more, depending on the species (fig. 5). When its appetite is 
finally satisfied the webworm deserts the old burrow and in the earth 
near by constructs its cocoon (fig. 6), a neat little chamber with stiff 
walls of silk and earth, the whole about the size and shape of a peanut 
meat, although this often has a short neck or tube at one end opening 
: at the surface of the 
ground. In this co- 
coon the worm awaits 
the change that shall 
transform it to the 
pupa or chrysalis (fig. 
Oe This perio or 
waiting may vary in 
length from a few days 
to several months, de- 
pending on the par- 
ticular species. The 
chrysalis is reddish- 
brown, helpless, and immovable except for the pointed abdomen, 
which can be rapidly rotated when it is disturbed. 
After a period of from 10 days to 2 weeks in the chrysalis stage, 
the moth (fig. 8) emerges from the chrysalis and forces her way 
out through the silken tube to the open air above, where, after a few 
Fig. 4.—Egegs of a webworm moth. Much enlarged. 
Fic. 5.—Caterpillar of the black-headed sod webworm. 
About three and a half times natural size. 
