New York AGRICULTURAL EXPERIMENT STATION. 401 
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of the worms until considerable damage has been done. In other 
words, no insecticide is applied until fall, and then not until after 
the worms are nearly one-half grown, with the result that never 
more than one-half of them are destroyed. A third reason, and 
one on which the preceding partially depends, lies in the habits of 
the cabbage worm and its butterfly and of the cabbage looper and 
its moth. ‘To show these the life history of each must be briefly 
reviewed. 
CABBAGE WORM. 
(Pieris rapae. ) 
LIFE HISTORY AND HABITS. 
Worms of the last fall brood pass the winter in the chrysalid 
or pupal form. ‘These chrysalids are attached to the under side 
of rails, sticks and dry weeds, and also to the sides of buildings or ~ 
any place where they can obtain some protection from excessive 
moisture. 
The white butterflies issue from the chrysalids the latter part 
of April and during May. They sometimes appear early in April, 
if the weather is warm for several days. After pairing, the 
female butterflies lay their eggs on whatever suitable plants can 
be found at that season of the year, on old stumps of cabbage grow- 
ing in neglected fields, cabbage set out for seed purposes, Early 
_ Wakefield cabbage, Siberian kale (“ sprouts”) and on such weeds 
as wild radish, mustard and cresses. Probably, on Long Island, 
the latter plants, especially wild radish, are the principal ones on 
which the worms of the first spring brood exist. The eggs of the 
butterflies are usually deposited singly on the lower and outer 
surface of the leaf, each female butterfly laying from 
100 to 300 eggs. The egg laying of the first brood ex- 
tends over a period of about 8 weeks. From 5 to 10 
days are required for the eggs to hatch. After hatching from 
the egg the worms feed for a period of about 10 or 12 days. 
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