THE CANADIAN ENTOMOLOGIST. 235 



the result, from the view that the inclination to revert is great, that even 

 with the first summer generation, which were the longest exposed to the 

 summer climate, always a portion of the pupae, without artificial means, 

 emerged telamonides, but another portion marcellus. This last will now 

 become telamonides by the application of cold ; the first, on the contrary, 

 will wholly or in part revert to the original form Walshii. One would 

 expect that the second and third generations would revert still more 

 easily, and in greater percentage than the first, because these last had 

 first taken the new form marcellus, but from the experiments so far made 

 can no other conclusion be drawn. To be sure, of the first summer 

 generation, only seven pupae out of sixty-seven over-wintered and 

 emerged telamon 'ides ; while of the second generation forty out of seventy- 

 six over-wintered ; of the third twenty-nine out of forty-two. But for 

 closer conclusions more extended experiments will be necessary. 



After the experiments so far had, one might still incline to the suppo- 

 sition that through seasonal-dimorphism the outside influences working 

 directly upon single individuals would force upon them one or the other 

 form. But this is not tenable. That cold does not bring one and heat 

 the other form follows from this, that with ajax each generation produces 

 both forms. Further, the author often reared the last, or over-wintering 

 generation of levana in the warmth of a room, and yet always got the 

 winter form. The length of the pupa period does not determine in 

 individual cases the form of the butterfly, or consequently determine 

 whether the winter or summer form shall emerge, but the length of the 

 pupa period is dependent upon the tendency which the growing butterfly 

 has taken in the pupa. As a rule, the two winter generations of ajax 

 emerge only after a pupa period lasting from 150 to 270 days, but single 

 cases occur in which the period is no longer than with the summer form 

 (14 days). With levana, too, occurs a similar phenomenon, for not only 

 was the winter form forced to a certain degree by artificial warmth during 

 the pupa period, but the summer generation produced many reverting 

 forms without the period having been at all protracted. The half way 

 reverting form porima was known long before any one thought of pro- 

 ducing it artificially by the influence of cold. It appears in midsummer 

 on the wing occasionally. * * * If the explanation, 



then, is correct, the winter form is the primary and the summer form the 

 secondary, and such individuals as embrace either naturally or artificially 

 the winter form are to be considered as examples of atavism. It appears 

 also that the individuals of a species are influenced by climatic change to 



