196 DIVERSITY OF THE SEXES 



scales covering veins and membrane indiscrimi- 

 nately, but usually, and in our native butterflies 

 always, occupying the middle of the front wing 

 and crossing the median veins obliquely near their 

 base [Fig. 163]. This dash is variously formed, 

 but the scales which compose it are usually much 

 larger than the ordinary scales, are black and 

 often partially erect ; they may also differ in vam 

 ous parts of the patch itself and alter their char- 

 acter abruptly ; for instance, some comparatively 

 huge and brilliant scales may occupy the middle 



line and be buttressed by 

 a multitude of minute 

 crowded, lustreless 

 FIG. i63.-ForewingofThymeii- scales ; or there may be 



cus Aetna, showing the oblique , , /. 



patch or stigma peculiar to the at One point a SOrt OI 

 males, X 2. . . 



whirlpool of large parti- 

 colored scales, set at all angles ; next it similar 

 scales, imbricated in the most regular fashion, like 

 the normal scales ; and beyond them again a multi- 

 tude of the minute, crowded, lustreless scales ; 

 these peculiarities, however, must be studied 

 with a glass ; the naked eye may indeed discover 

 that the patch differs in different insects, but the 

 general effect, in all alike, is a variably formed 

 velvety patch or oblique streak of black. 



Before leaving the wings, I will call attention 

 to one striking fact. Wherever antigeny, colora- 

 tioual or structural, manifests itself in the wings 



