INJURIOUS TO CABBAGE AND RELATED CROPS 13 



j^A'T 



are dull gray. When at rest the moth has the wings slightly 

 turned up at the tip and the antennae are held extended forward. 

 The female moth deposits her minute whitish or yeflowish eggs, 

 Yt inch in diameter, singly or in groups of two or three, usually 

 on the leaves. Each 

 moth is capable of lay- 

 ing on an average 

 nearly 300 eggs during 

 a period of one to two 

 weeks. They hatch in 

 three to six days and 

 the young caterpillars 

 first eat holes in the 

 leaf from beneath but 

 do not cut through to 

 the upper surface. Later the upper epidermis dies, turns brown 

 and drops out leaving the leaf riddled with holes. Sometimes 

 in cool weather the young larvae live as miners in the leaf for 

 two to four days. The caterpillars are very active when dis- 

 turbed, wriggle from the leaf and suspend themselves by a thread 

 till the danger has passed. The larva reaches maturity in nine 



to twenty-eight days. 



ti\ 



Fig. 14. — The diamond-back moth, male 

 (X3|). 



Fig. 15. — Cocoon of the diamond-back moth 

 showing the larva within ( X 4) . 



It is then only about 

 f inch in length, pale 

 green in color and 

 sparsely clothed with 

 small, erect black hairs ; 

 the head is brownish 

 yellow mottled with 

 black. The larvae be- 

 month and spin their beautiful open- 

 so loosely woven that the pupa can 

 on the underside of the leaves. In 



come mature in about a 

 work cocoons (Fig. 15), 

 be plainly seen within, 

 the summer from four to thirteen days are spent in the pupal 



