20 THE COMMONER BUTTERFLIES. 



the male sex, the spring individuals being uniform chrome 

 yellow above, while the October males are of a whitish yel- 

 low and the hind wings are dusted with gray. 



11. Some Remarkable Differences between the 



Sexes. 



Many male butterflies may be readily distinguished by 

 characteristic tufts, rows, or wisps of hairs or patches of 

 special scales or membranous folds generally rendered in 

 some way conspicuous, and which do not occur in the 

 female. Of the first we have a good example in our 

 species of Argynnis, which show a row of long semi-recum- 

 bent hairs on the upper surface of the hind wings between 

 the costal and subcostal nervures; of the second in the 

 mealy-looking margins of the upper surface of the wings 

 of Callidryas, tlie discal patch on the fore wings of many 

 Hair-streaks, the apparently blackened and thickened veins 

 of the fore wings of Argynnis, or the discal streak accom- 

 panied by large tilted scales so common in the Smaller 

 Skippers; of the last in the blackened pocket of the hind 

 wings of Anosia, the plaited fold of the hind wings of 

 Laertias, or the deftly inconspicuous costal fold of the 

 Larger Skippers. 



These very patches or folds usually conceal scales differ- 

 ing to a greater or less extent from the surrounding scales 

 and peculiar to the males, called scent-scales or androconia, 

 i.e., male-scales. They do not, however, always occur in 

 these patches (where they are usually concealed from vicAV 

 to some degree), but may be simply scattered among the 

 other scales and then, being almost invariably much 

 smaller, almost completely concealed from view. 



While the ordinary scales of butterflies, common to both 

 sexes, show very little variety in their structure, being 

 striate, more or less fan-shaped or shingle-shaped lamina? 



