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APPLIED ENTOMOLOGY 



The insect passes the winter as a pale brown chrysahs (Fig. 313d) 

 about three-quarters of an inch long, attached in some protected place. 

 The adults emerge in the spring and lay their eggs singly (Fig. 3136) 

 on the leaves of cabbage, cauliflower, mustard, nasturtium and other 

 plants of the family Cruciferse, and about a week later the caterpillar 

 hatches and begins to feed. At first it is pale green, but when full- 

 grown, after about 2 or 3 weeks, is a soft, velvety-green, and about an 

 inch long (Fig. 313c). At first it feeds on the under surface of the 



Fig. 313. — Cabbage Butterfly {Pontia rapce L.) : a, adult, slightly enlarged; b, egg, 

 from side and from above, considerably enlarged; c, caterpillar, somewhat enlarged; d, 

 chrysalis, somewhat enlarged. (From U. S. D. A. Farm. Bull. 856.) 



leaf, but after growing, eats holes through and may leave only the veins. 

 It often bores into the forming heads also, in search of more tender food. 

 It feeds for from 2 to 3 weeks, then pupates for a rather shorter period, 

 at the end of which time the adult emerges and lays eggs for a second 

 generation. There are usually two or three generations in the Northern 

 States and as many as five or six in the South. 



Where these insects are abundant they cause considerable injury, 

 not only to the leaves but by boring into the heads, reducing their value. 



Control. — Spraying with a stomach poison, preferably arsenate of 

 lead, a little stronger than the standard formula, as soon as the cater- 

 pillars appear in the spring, is a successful treatment, but as the spray 

 tends to run off the smooth leaves of the plants, the addition of a little 

 soap as a "sticker" is desirable. If the larvae of the first generation 

 are killed for the most part by this, later applications will generally prove 

 unnecessary. In some cases the poison is dusted on instead of sprayed. 



