IMKKIXAK: I'lHHIS llAPAK. 1213 



aoea, in all places except in {hv. Iiill re.nioiis, where cultivation is scarce. 

 The reason for tliis is to he found in |)art, it seeni.s to nw. from the earlier 

 apptaranee of the hrixxls, the eaterpillurs ot' which thus get possession of 

 all th(! hcst fceilinu' iilace;;. 



Dimorphism and variation. As mentioned in the dcseri])tive por- 

 tion, the early hrood of this butte.rHy, from wintering ehrysalids, differs 

 from the later broods. The spring hutterHies are smaller and of a duller 

 white than the t^umnier hutterHies, with broader black markings on the 

 middle and ti|) ot' the wing, and the base sprinkled with black atoms, 

 which are almost entirely wanting in the sununer butterflies ; beneath, 

 where the markings are most conspicuous and varied, there is a j)owdery 

 streak of black scales along the middle of the hind wings of the spring 

 butterflies, which is nuich less conspicuous in the later broods. These 

 differences apjiear ctpially in Kiu'ope and America. Those wishing to 

 investigate the variations of this butterfly geographically will do well to 

 study the observations of Mayer (Stett. ent. zeit., xii : 151), Staudinger 

 (Horae ent. ross., vii:3o) and Speyer (Stett. ent. zeit., xliii:376). 



These same seasonal distinctions also appear in the yellow variety no- 

 vangliae, which was first observed in Canada by Bowles, and mentioned by 

 hiui in his paper published in 1864. Although this variety doubtless occurs 

 in Europe, as shown by Bowles's reference to Curtis's statement in his 

 Farm Insects, afterwards repeated by Fernald (Can. ent., xv : 237), it is 

 undoubtedly of excessive rarity, as it was unknown to Stainton and to 

 Boisduval, neither of whom had seen it until I showed it to them ; nor was 

 it knoAvn to any of the French entomologists present at a meeting of the 

 Paris society where I showed (Bull. soc. ent. Fr. , Apr. 21, 1873) the 

 specimen I afterwards gave to Boisduval, and which is now in Oberthiir's 

 collection. Nor have I seen any subsequent notice of such a form. With 

 us it was estimated to have occurred about once in five hundred cases, 

 which is by no means excessively rare in such a common insect, and half 

 a dozen have been bred from one batch of larvae ; but the interesting 

 thing is that it is now excessively scarce ; the free chance of multiplying 

 and the new order of things which this insect found on its introduction to 

 this country, seem to have given it a chance to develop this variety, 

 merely {)otential in Europe ; but now that parasites have come to the fore, 

 the reaction from the disturbed order of nature has set in, and the 

 creature is held in check as in Europe, with only occasional and local out- 

 bursts, the variety no longer appears except in instances which may bear 

 comparison with the European. Possibly, however, it keeps company 

 with the pioneers. The disappearance of this variety is as interesting as 

 its apparition. I have not heard of it from further west than jNIichigan, 

 and the last specimen seen by me on the wing in New England was in 

 1878. 



