THE HORSE-RADISH WEBWORM. 
73 
Their most noticeable injury is caused by checking the first growth 
of the plants early in the spring and destroying the blossom buds. 
The pupae (fig. 27) are pale yellow marked with brown and are 
inclosed in cocoons. The cocoons (fig. 28) are placed on leaf petioles 
or among dead leaves and are exquisitely beautiful, silver-gray, lace- 
like, cigar-shaped objects. 
LIFE HISTORY. 
There are four generations each year and activity is continuous from 
the last da}^s of March until well into October. A few of the larvae 
of the fourth generation mature and produce moths in late September 
or October, but the majority live through the winter among dead 
leaves or in cracks in the soil and develop into moths the following 
April. The hibernating larvae may vary from 
very small to nearly mature specimens. The 
moths are remarkably long lived and egg-laying 
extends over a considerable period. The genera- 
Fig. 27.— The horse-radish 
we b worm: Pupa. Greatly Fig. 28.— The horse-radish webworm: Cocoon. Greatly 
enlarged. ' (Original.) enlarged. (Original.) 
tions overlap to such an extent that it is practically impossible to 
separate them in the field. The details of the generations and stages 
are given in the rearing records which follow. 
REARING RECORDS. 
On April 3 several overwintered larvae were collected from horse- 
radish and placed in a cage. The record is as follows: 
Apr. 3 Larvae collected. 
Apr. 4 i First cocoons formed. 
Apr. 6 First larvae pupated. 
Apr. 23 First adults issued. 
On April 24 a pair of these moths mated and were placed in a 
separate cage containing horse-radish leaves and diluted honey. The 
record is as follows : 
First generation. 
Apr. 24 Moths mated. 
Apr. 25 First eggs deposited. 
May 3 First eggs hatched. 
May 25 First cocoons formed. 
May 26 First larvae pupated. 
June 3 First adults issued. 
