1628 THE BUTTERFLIES OF NEW ENGLAND. 



tioned wlictlier seasonal diniorpliisin should not have been discussed first, 

 and wlietlier it may not be tlie primal form of dimorphism in general, 

 for I believe there is not a single instance in our fauna where dimorphism of 

 any kind (excepting antigenic) occurs in a monogoneutic butterfly. 



But however this may be, we have in not a few of our butterflies in- 

 stances of seasonal dimorphism ; indeed the successive broods of the same 

 b Litterfly which appear in a single season almost always differ from each 

 other ; often so incredibly as to be mistaken for distinct species. 



The imported cabbage butterfly is a case in point ; tiie spring butter- 

 flies are smaller and of a duller white than the later broods, with broader 

 black markings on the middle and tip of the wing, and the base sprinkled 

 with black atoms, which are almost entirely wanting in the other broods ; 

 beneath, where the markings in this genus are most conspicuous and 

 varied, there is a powdery streak of black scales along the middle of the 

 hind wings, which, in the later broods, is much less conspicuous. 



A somewhat similar distinction occurs in its near ally, the Gray-veined 

 White. Tlie summer brood of this species is almost pure white, while the 

 spring brood, besides being smaller, has the under sui'face of the hind 

 wings and of the tip of the fore wings heavily washed with yellow, and all 

 the veins in the same area broadly sprinkled with dark scales. Moreover, 

 in all the whites, the hind wings of the second generation are longer than 

 those of the first. 



In the American Copper, spring individuals are of a more fiery red, and 

 the orange band of the under surface of the hind wings is broader ; while 

 in later broods the markings are less vivid and less distinctly marked, and 

 there is a longer tooth on the margin of the hind wings. 



In our Pearl Crescent, according to the discovei'ies of Mr. Edwards, the 

 spring type (which he formerly considered a species distinct from the 

 summer type, but wliich he has since bred from the latter) is characterized 

 by the purple or pearly hue of the under surface of the hind wings, and by 

 heavier markings on the same wings ; especially by the presence of great 

 patches of ferruginous or dusky color at the outer margin ; markings which 

 usually are only indicated in the summer broods, wliere the color is deli- 

 cately traced with feiTuginous lines ; in the spring butterflies the black 

 markings of the upper surface are also heavier and more diflTuse than in the 

 later broods. 



A further instance, perhaps the most striking that we have, is in the 

 often quoted case of Iphiclides ajax, whose changes have been so thoroughly 

 worked out by Mr. Edwards. Here each form appears at a different 

 season of the year ; marcellus is the early spring type, telamonides the 

 late spring, and ajax the summer and autumn type. Nearly all the butter- 

 flies which, in West Virginia, emerge from the chrysalis before the middle 

 of April are marcellus; between that and the end of May, telamonides; 



