On the Seasonal Dimorphism of Butter flies. 33 



generally only reaching the intermediate form 

 known as Porima. Now it would, at all events, 

 be astonishing if with P. Ajax the reversion were 

 always complete, as it is precisely in this case that 

 the tendency to individual reversion is so variable. 

 I might, for this reason, suppose that one of the 

 two winter forms, viz. the vax.Walshii, is nothing 

 else than an incomplete reversion-form, corre- 

 sponding to Porima in the case of A. Levana. 

 Then Telamonides only would be the original 

 form of the butterfly, and this would agree with 

 the fact that this variety appears later in the 

 spring than Walshii. Experiments ought to be 

 able to decide this. 20 The pupae of the first 



80 [Eng. ed. Edwards has since proved experimentally that 

 by the application of ice a large proportion of the pupae do 

 indeed give rise to the var. Telamonides. He bred from eggs 

 of Telamonides 122 pupae, which, under natural conditions, 

 would nearly all have given the var. Marcellus. After two months' 

 exposure to the low temperature there emerged, from August 24th 

 to October i6th, fifty butterflies, viz. twenty-two Telamonides, 

 one intermediate form between Telamonides and Walshii, eight 

 intermediate forms between Telamonides and Marcellus more 

 nearly related to the former, stx intermediate forms between 

 Telamonides and Marcellus, but more closely resembling the 

 latter, and thirteen Marcellus. Through various mishaps the 

 action of the ice was not complete and equal. See the 

 "Canadian Entomologist," 1875, p. 228. In the newly dis- 

 covered case of Phyciodes Tharos also, Edwards has succeeded 

 in causing the brood from the winter form to revert, by the 

 application of ice to this same form. See Appendix II. for 

 a resume of Edwards' experiments upon both Papilio Ajax and 

 Phyciodes Tharos. R,M.] 



D 



