322 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



to New England, reached New York in 1868, Cleveland, Ohio, by 

 1875, and the Gulf States by 1880, and has since spread to all parts 

 of the country. 



The butterflies are among the first to emerge in early spring. 

 They are white, marked with black near the tip of the fore-wings, 

 which expand nearly 2 inches. The female bears two black spots 

 on each fore-wing, while the male has only one, and both sexes have 

 a black spot on the anterior margin of the hind-wings. 



Life History. The butterflies soon commence to lay their eggs 

 on whatever food-plant is available. The larvae feed on all of the 

 common cultivated crucifers as well as many wild sorts, so that the 

 species is never without food. The small yellowish, oval eggs are 



FIG. 271. Pteromalus puparum, a chalcis-fly which parasitizes the cabbage 

 worm and many other injurious insects, male and female greatly enlarged 

 hair line shows natural size. (After Chittenden, U. S. Dept. Agr.) 



laid on end .on the foliage, and are marked with prominent longi- 

 tudinal ridges. They hatch in from four to eight days. The larvse 

 grow very rapidly, gorging themselves on the foliage, which they 

 skeletonize in their well-known manner, and become full grown in 

 from ten days to two weeks. The mature cabbage worm is about 

 li inches long, of a velvety green color, very similar to the foliage, 

 with a faint yellow stripe down the middle of the back and a row 

 of yellow spots on each side. The surface, when seen under a 

 lens, is finely roughened and dotted with small black specks. The 

 chrysalis is attached to the foliage by a strand of silk around the 

 thorax and is first greenish and later light brown in color. The 

 butterflies emerge in from one to two weeks in the summer, but 

 the chrysalides of the last generation in fall hibernate over winter 

 among the old stalks and rubbish on the fields. Thus the whole 

 life cycle in summer requires from three to five weeks. In New 



