298 



APPLIED ENTOMOLOGY 



spread within certain limits, but only within these, and this applies to 

 other animals and to plants as well. 



Family Papilionidae (The Swallow-tails). The butterflies of this 

 group are nearly all large, and with a backward-projecting lobe or 

 tail on the hind wing. One species or another may be seen in almost 

 every part of the country but they rarely do much injury, feeding for the 

 most part on plants of little importance. The Black Swallow-tail 

 Butterfly (Papilio polyxenes Fab.) is probably the most important species, 

 as it occurs all over the United States and feeds on celery, carrots, par- 

 snips and other plants. 



FIG. 317. Celery Butterfly (Papilio polyxenes Fab.): a, full-grown caterpillar; b, 

 head of same showing osmaterium extended; c, male butterfly; d, outline of egg; e, young 

 larva; /, chrysalis. All about natural size except d, which is much enlarged. (From U. 

 S. D. A. Farm. Bull 856.) 



The butterfly (Fig. 317c) spreads between three and four inches, and 

 its wings are black with two rows of yellow spots crossing each wing, with 

 blue shadings between the two rows on the hind pair. There is also a 

 black spot surrounded by orange on the outer part of the hinder margin 

 of the hind pair. In the male the inner row of yellow spots becomes a 

 band on the hind wing. 



In the South the butterflies winter over, but in the North this period is 

 spent as the pupa. Eggs are laid singly on the leaves of the food plants, 

 and hatch in about 10 days. The caterpillars feed for from 10 days to 

 several weeks, then form their chrysalids (pupae) on some part of the plant 

 (Fig. 317f) and in from ten days to 2 weeks more the adult butterflies 

 emerge. There are two generations in the North and more in the South. 



