6 Farmers’ Bulletin 1258. 
structive work not only in the spring when conditions are favorable 
for grass growth, but throughout the whole summer and even during 
the fall. Different species or additional generations of the same 
species follow one another so that at any time throughout the growing 
season these pests may be found actively at work. Especially in times 
of drought and when plant food is insufficient to permit rapid, thrifty 
growth, the sod webworms may consume practically all the growth as 
fast as it appears, thus leaving nothing for the owner of the land. In 
fact, there are on record several well-authenticated instances where the 
worms have stripped whole pastures and hay fields absolutely bare; 
in one instance, occurring in New York State, farmers of several 
counties found it necessary to dispose of their cattle because of the 
shortage of feed which resulted from the work of these insects. That 
such serious injury does not occur more often is due only to a com- 
bination of natural influences which prevents these worms reaching 
devastating numbers, and if at any time one or more of-such forces 
fail to act, destruction and loss are likely to result. 
WEBWORMS AND PARENT MOTHS. 
Webworms are the caterpillars or young of certain small whitish 
moths or millers which are readily to be observed in meadows or 
pastures, particularly toward dusk. They are quite conspicuous 
when flying; but because of their peculiar habit of folding their 
wings closely about their bodies when at rest, they are often very 
difficult to see after they have alighted on a grass stem or leaf. There 
are many sorts of webworms, some 60 or 80 kinds being found in the 
entire United States, all of which are very much alike in both larva 
and moth stages. Practically all of these insects feed on grasses, but 
less than a dozen of them are of agricultural interest, as the others 
either attack unimportant wild grasses or are so rare that they are of no 
economic importance. All of them have the same stages in their life 
history but vary considerably in their seasonal history, and a knowl- 
edge of these differences is sometimes essential in planning control 
measures. 
GENERAL LIFE HISTORY. 
The eggs (fig. 4) are very small and are dropped indiscriminately 
by the female moths as they fly about over the grass at dusk and dur- 
ing the early hours of the night. Being dry, these eggs fall down 
among the grass stems and are therefore difficult to find. They hatch 
in a week or 10 days, and the young worms at once begin to feed on 
the grass leaves about them, cutting small pits in their surfaces. 
They immediately start the formation of the protective silken net 
within which they remain during their whole larval life. As they 
