IN COLORING AND STRUCTURE. 193 



other birds, and, in direct opposition to the feat- 

 ures we have been discussing, they are wholly 

 confined to the males. 



In butterflies structural antigeny is mostly con- 

 fined to the wings and the legs. Sometimes it 

 affects the contour of the wings ; one of the most 

 conspicuous cases among our own butterflies is in 

 the Coral Hair-streak (Strymon Titus), where the 

 front wings of the male have a pointed tip, and 

 the hind wings have the inner angle sharply de- 

 fined ; while in the female both the tip of the 

 front wings and the inner 

 angles of the hind wings 

 are rounded. Another 

 maybe seen in the two FIG. m-veins of fore wing of 



Thecla Calanus ; a, male ; 6, fe- 



emperor butterflies rep- male ? nat. size. 

 resented in Figs. 182 and 184, 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. 

 Or it 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 

 of the front wings ; but occasionally it is very 

 marked, as in many of the hair-streaks [Fig. 

 160], where the branches of the subcostal vein 

 near the end of the cell are thrown far out of 

 place to accommodate a patch of peculiar crowded 



