60 
PAPERS ON INSECTS AFFECTING VEGETABLES. 
winter. It will thus be seen that about half the webworms of the 
second generation and all of those of the third generation, which 
have not been destro}^ed by parasites or through artificial or natural 
agencies, live through the winter in their tubes in the soil. These 
u worms " pupate late in the spring and the moths which issue deposit 
eggs for the first generation. 
The moths when depositing eggs are often to be found in the beet 
fields in enormous numbers, and when disturbed may be seen flying 
close above the beet leaves in " clouds." When such numbers of moths 
are observed in a beet field they should serve as a warning to the 
fig. 11. 
-A medium sized sugar-beet plant defoliated by the sugar-beet webworm in July. 
(Original. I 
grower that a " crop " of webworms may be expected within the next 
week or 10 days. 
As a rule the first and second generations are the most destructive, 
the third generation, which is actually only a partial one, rarely 
causing serious damage. It seldom happens that the "worms" of 
successive generations infest the same patch of beets to a serious ex- 
tent. Thus a certain field ma} T be infested by the webworms of the 
first generation, while the moths which develop from them may drift 
to adjoining fields to deposit eggs for the next generation. 
The webworms often appear very suddenly and apparently with- 
out warning in certain fields, and it is not uncommon for the growers 
to express the idea that they have migrated from adjoining fields. 
