872 THE BUTTERFLIES OF NEW ENGLAND. 



The eo-o-8 are of a depressed echinoid shape, covered with strong and 

 rather coarse prominences and ridges, arranged with a certain degree of 

 regularity. 



The caterpillars are somewhat elliptic as viewed from above, pretty 

 regularly arched, but highest in front ; they are generally green with a 

 darker dorsal stripe and a lateral series of darker, slender, oblique stripes 

 or streaks. 



The chrysalids are about twice as long as broad, well rounded and 

 arched, the surface covered with a delicate lace-work of raised lines ; they 

 are usually dark, dull brown. 



EXCURSUS XXXI.— SEXUAL DIVERSITY IN LEGS, WINGS 

 AND SCALE ARRANGEMENT. 



Eftsoones that Damzell, by her heavenly might, 

 She tuni'd into a winged Butterflie. 

 In the wide aire to make her waudring flight ; 

 And all those flowres, with which so prentiouslie 

 Her lap she filled had, that bred her spight, 

 She placed in her wings, for memorie 

 Of her pretended crime, though crime none were : 

 Since which that Flie them in her wings doth beare. 

 Spenser.— JtfaiopoJjnos. 



In a previous excursus on antigeny* we called attention to some of the 

 differences between the sexes as seen at first glance in the color or color 

 pattern of the wings. Antigeny, however, does not confine itself to such 

 superficial appearances. It is seen quite as much in the more essential 

 features of the structure, in the wings, the legs, and occasionally e-\'eu in 

 the antennae. 



Sometimes it affects the contour of the wings. Indeed, it is a very 

 common thing to see such differences as appear in Chlorippe, illustrated 

 on pi. 16, fig. 7, where, besides minor differences, the hind wings of the 

 female are full and rounded, while those of the male are angulate, the 

 outer margin being nearly straight. The hind wings of our species of 

 Pieris also differ considerably, those of the male being more prominent at 

 the extremity of the subcostal nervules while those of the female are more 

 regularly rounded . But the most conspicuous case among our own but- 

 terflies is in Strymon titus, where the fore wdngs of the male have 

 a pointed tip, and the hind wings have the inner angle sharply defined ; 

 while in the female both the tip of the fore wings and the inner angle of 

 the hind wings are broadly rounded. 



So, too, sexual dimorphism may affect the direction of the veins of the 

 wings ; usually the difference between the sexes is slight and concerns the 

 point of origin of one or two of the upper branches of the subcostal vein 



» See p. 531. 



