412 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



wanting, and the hind-wings are covered with pale-blue scales 

 on the posterior half. There is considerable variation, however 

 in the color of both sexes. 



Life History. In the North the winter is passed in the chrysalis 

 stage and the butterflies appear in May in New England, while in 

 the far South the butterflies hibernate over winter and appear in 

 March or April. The eggs are laid on the foliage and are of globu- 

 lar form, about one-twenty-fifth inch in diameter, at first 

 pale honey-yellow, but later reddish-brown. The eggs hatch in 

 from four to nine days. The young larva? are quite dissimilar 

 from the older stages, being nearly black with a white band around 

 the middle of the body (Fig. 297, e) . The larva; feed exclusively 

 on umbelliferous plants, including besides those mentioned, cara- 

 way, fennel, parsnip, dill, wild carrot, wild parsnip, and other 

 weeds of this family. The full-grown larva is shown, natural 

 size, in Fig. 297, a. It is bright green, sometimes yellowish, and 

 marked with rings and spots of velvety black as illustrated. Just 

 back of the prothorax is a pair of membranous yellow horns called 

 osmateria, which give off a peculiar pungent odor, which is quite 

 disagreeable and evidently aids in frightening away enemies. 

 These osmateria are soft, retractile organs, Avhich are drawn back 

 between the segments and are extruded only when the larva is 

 disturbed. 



In the far South the larva will become grown in ten days, but 

 in the Xorth it requires three to four weeks. The caterpillar 

 then attaches itself to some part of the plant by the anal prolegs, 

 and fastens a strong loop of silk around the thorax, and sheds its 

 skin, leaving the chrysalis or pupa firmly attached to the leaf or 

 stem as shown in Fig. 297, /. The chrysalis is a dull gray color 

 marked with black and brown and about 1^ inches long. In from 

 ten days to two weeks the butterfly emerges from the chrysalis. 

 Thus the complete life cycle may be passed in twenty-two days in 

 the South to eight weeks in the North. In the North there are 

 but two generations a year, while in the South there are probably 

 three or four. 



Control. The caterpillars are so readily seen, and if not seen 



