316 THE BUTTERFLIES OF NEW ENfJLANI). 



EXCURSUS IX.— DIMORPHISM AND POLYMORPHISM. 



Who loves not the gay butterfly, whieh flits 



Before him in the ardent noon array'd 



In crimson, azure, emerald, and gold; 



With more magnificence upon his wing — 



His little wing — tnan ever graced the rol)e 



Gorgeous of royalty, is like the kine 



That wanders mid the flowers that gem the mead, 



Unconscious of their beauty. 



Carrington. 



Amoxg the subjects of general philosophical interest which the study 

 of animals during the Darwinian epoch has brought to notice, few have 

 excited more attention and interest than the existence in a vast number 

 of animals of two or more distinct forms in the same species. That 

 this is very commonly true of the two sexes goes without saying ; but 

 besides this it often happens that one sex may appear under two distinct 

 guises, or that alternate broods of the same animals may differ so much 

 from each other as in many cases to deceive the most acute naturalist into 

 the very reasonable belief that they are distinct species. Much attention 

 has been given to this subject among the butterflies, and we have in our 

 native species a considerable niunber of instances in illustration. A large 

 proportion of them show, in some peculiarities of the scales of the male 

 sex and their arrangement into special patches, a ready distinction from 

 the opposite sex, which is to be compared with such characteristics among 

 birds as the special plumage assumed by the cock in his comb, wattles, 

 arching tail and spurs. But just as the cock frequently differs further from 

 the hen in the character of the plumage covering the whole body, so there are 

 a very large number of butterflies which also differ from the opposite sex 

 in the general color or pattern of the upper or lower surface of the wings. 

 Curiously enough, Avhen we consider how very generally the under surface 

 of the hind wing is variegated in butterflies, we rarely find in this place 

 any distinction between the sexes. It is largely confined, at any rate with 

 the butterflies of the temperate zone, to the massive coloring of the upper 

 surface, and here, whenever one of the sexes departs from the typical 

 coloring of the group to which it belongs, in order to assume a livery 

 distinct from its mate, it is almost always the female, at least among 

 our own butterflies, which is thus distinguished. We have indeed but a 

 single example, that of Cyaniris pseudargiolus, in which the opposite is 

 true. 



But besides that form of dimorphism which simply intensifies the distinctions 

 between the sexes, we have in some cases a double dimorphism, so to speak, 

 which not only distinguishes one sex from the other, but divides the mem- 

 bers of one of the sexes into two distinct groups, one of which more nearly 

 resembles the male, while the other may depart widely from it. We 

 find several such instances among the lihodoceridi. There are cases, 



