448 The Moths and Butterflies 



species with more translucent fore wings, is found only on the Pacific coast 

 and in the Wyoming mountains. I have seen P. smintheus in great numbers 

 in the beautiful flower-dotted glacial parks of Colorado from an altitude 

 of 6000 feet upward. The wings are so thinly scaled that they are nearly 

 translucent, and the scales themselves are narrow and club-like, so different 

 indeed from those of other butterflies that they probably have some special 

 function not yet understood. The larvae are "flattened," having a some- 

 what leech-like appearance; they are black or dark brown in color, marked 

 with numerous light spots. The chrysalis is short and rounded at the head, 

 and pupation takes place on the surface of the ground, among leaves and 

 rubbish, a few loose threads of silk being spun about the spot in which trans- 

 formation occurs. 



The swallowtails (Fig. 639), all except five of which belong to the genus 

 Papilio (a name given them a century and a half ago by Linnaeus, the first great 



classifier of animals and plants), are readily 

 distinguished by the longer or shorter "tails," 

 one to three, which project backward from 

 the hind wings. The ground color is black, 

 sometimes suffused with metallic bluish or 

 greenish, and the markings consist of yellow 

 or greenish-white bands and blotches together 

 with a few red, orange, and blue eye-spots on 

 the upper and under sides of the hind wings. 

 The larvae are large, cylindrical, fleshy, naked 



caterpillars usually conspicuously banded or 

 FIG. 640. Chrysabd of a swal- r 



low-tailed butterfly, Papilio sp. spotted with green, black, yellow, orange, 

 (Natural size.) an d white. They are provided with a pair 



of fleshy and flexible colored "horns" (osmateria) which can be protruded 

 from, or withdrawn into, the front thoracic segment and which give off a 

 strong musky scent sufficiently disagreeable to repel many threatening 

 enemies of the caterpillar. The chrysalids (Fig. 640) are naked, sus- 

 pended by the tail from a silken button and supported by a silken girdle 

 or "bridle." They often mimic very closely the coloration and surface 

 configuration of the tree-trunk or other object to which they are attached 

 (Fig. 640). Poulton, an English naturalist, has been able to obtain chrys- 

 alids of a single swallowtail species of many different colors by enclosing 

 the larvae just before pupation in separate boxes lined with paper of different 

 colors. The color-tone of the chrysalid tended strongly toward that of the 

 environing paper. Such a color plasticity is certainly of much advantage 

 to the insect in rendering the exposed and defenceless chrysalid indistin- 

 guishable. (See Chapter XVII for a discussion of "color and its uses.") 

 One of the best-known butterflies of the east is the zebra swallowtail, 



