20 MANUAL OF VEGETABLE-GARDEN INSECTS 



f inch in length, bristly, with the body tapering at both ends. 

 The back is purplish brown to dark greenish black. There is a 

 yellow^ stripe running through the spiracles and the underside 

 of the body is dull greenish. The head is black, the cervical 

 shield is black on the sides and the body is marked with numer- 

 ous black tubercles. 



The larv?e become full-grown in a little over a month and 

 construct thin silken cocoons covered with dirt at or just below 

 the surface of the ground. The larvae of the summer brood soon 

 transform to pupae but those of the fall brood remain in the 

 larval condition until the following spring. The pupa is about 

 J inch in length and brownish in color. The moth has an ex- 

 panse of nearly an inch. The front wings are bright straw- 

 yellow crossed with two fine brown lines and the veins are 

 more or less lined with brown. On the outer margin of the 

 wing there is a broad, brown shade inclosing a triangular straw- 

 colored spot. The hind wings are straw-colored, translucent 

 white at the base with brown marginal and submarginal lines, 

 the latter usually incomplete and sometimes lacking. The 

 moth deposits her eggs in small flat masses of three to more than 

 a dozen, the eggs overlapping in the cluster. The egg is ovate 

 and very flat wdien first laid but gradually swells with the 

 development of the embryo. It is brownish yellow in color. 

 The egg hatches in eight days. There are two and possibly 

 three generations annually, the fall brood of caterpillars being 

 the most injurious. 



Fortunately the purple-backed cabbage worm rarely becomes 

 sufficiently abundant to require remedial treatment. Spray- 

 ing with arsenate of lead (paste), 2 pounds in 50 gallons of 

 water, should give satisfactory results. 



References 



Buckler, Ent. Mo. Mag. 19, pp. 126-130. 1882. 

 Fletcher, Rept. Ent. Canada for 1904, pp. 231-232. 



