THE HORSE-RADISH WEBWORM. 



73 



Their most noticeable injury is caused by checking the first growth 

 of the pls^nts early in the spring and destroying the blossom buds. 



The pupse (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 days 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 

 webworm: Pupa. Greatly- 

 enlarged. (Original.) 



Fig. 28. — The horse-radish webworm: Cocoon. Greatly 

 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 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. 



