LEPIDOPTERA 



741 



The ground color of the wings is black, which 

 is usually marked with yellow, and often 

 with metallic blue or green. The larvae of 

 our swallow-tails are never furnished with 

 spines, but are either naked or clothed with 

 a few fine hairs. In a single species that is 

 widely distributed in the United States, 

 Laertias philenor (Fig. 946) and in the genus 

 Ithobalus, which is represented in our fauna 

 only in the extreme South, the body of the 

 larva bears fleshy filaments. An osmeterium 

 is always present; this is bright colored, 

 forked, and is thrust out from the upper part 

 of the prothorax when the caterpillar is dis- 

 turbed. It diffuses a disagreeable odor. 

 See page loi. 



The chrysalids are thickened in the 

 middle and taper considerably at each end; 

 they are more or less angulated, and always 

 have two prominent projections at the an- 

 terior end. They are suspended by the tail 

 and by a loose girth around the middle (Fig. 



947)- 



There are about twenty species of swal- 

 low-tails in America north of Mexico. The 

 following well-known species will serve as 

 illustrations. 



The black swallow-tail, PapUio polyxenes. — The larva of this 

 swallow-tail (Fig. 948) is well-known to most country children. It is 

 the green worm, ringed with black and spotted with yellow, that eats 

 the leaves of caraway in the back yards of country houses. It feeds 

 also on parsnips and other imibelliferous plants. The first instar of 

 this larva is black, banded about the middle and caudal end with 

 white. There are two generations an- 

 nually in the North and at least three 

 in the South. 



In the adult the wings are black, 

 crossed with two rows of yellow spots, 

 and with marginal lunules of the same 

 color. The two rows of spots are much 

 more distinct in the male than in the female, the inner row on the 

 hind wing forming a continuous band crossed with black lines on the 

 veins. Between the two rows of spots on the hind wings there are 

 many blue scales; these are more abundant in the female. Near the 

 anal angle of the hind wing there is an orange spot with a black center. 

 On the lower surface of the wings the yellow markings become 

 mostly orange and are heavier. 



This species is foimd throughout the United States and in 

 the southern parts of Canada. In California the black swallow- 



Fig. 946. — Lcerttas phile- 

 nor, larva. (Fiom Ri- 



ley.) 



Fig. 947. — Chrysalis of Papilio. 



