CULTURAL DIRECTIONS 285 



upper surfaces. To accomplish this thoroughly seems 

 almost impossible with a power machine. 



365. The imported cabbage worm (Pontia rapae) is 

 generally recognized to be the most important insect 

 enemy of cabbage and several closely related crops. The 

 pest was first seen in North America in i860 at Quebec, 

 five years later in Maine. Now it is distributed through- 

 out the United States. The butterfly is familiar to all 

 garden makers. It is white, with a wing expanse of 

 nearly 2 inches. There are two conspicuous black spots 

 on each fore-wing of the female and only one on the 

 fore-wings of the male. The full grown larva is over an 

 inch long. It is nearly green and finely dotted with small 

 black spots. A faint yellow stripe marks the middle 

 of the back with a row of yellow spots on each side in 

 line with the spiracles. The pale yellowish eggs are de- 

 posited singly, and usually on the underside of the leaves. 



The butterflies appear early in spring, and in a few 

 days begin laying eggs, -which hatch in four to eight days, 

 the larvae attaining full maturity in from ten days to two 

 weeks. The chrysalis stage during the summer months 

 lasts from one to two weeks. The insect' also passes the 

 winter in the chrysalis form. There are three broods 

 in the North in one season. 



Several natural enemies of this pest assist the grower 

 in controlling it, but it is often necessary to use insecti- 

 cides. All points considered, arsenate of lead is proba- 

 bly the most effective poison in destroying cabbage 

 worms. Other remedies are hot water, kerosene emul- 

 sion, and pyrethrum. 



366. Other insect enemies. — ^The southern cabbage 

 butterfly (Pontia protodice), the cross-striped cabbage 

 worm (Evergestis rimosalis), the common cabbage looper 

 (Autographa brassicae), the imported cabbage web-worm, 

 the harlequin cabbage bug (Murgantia histrionica) , cut- 

 worms, flea-beetles and leaf-beetles. 



