228 THE CANADIAN ENTOMOLOGIST. 



AN ABSTRACT OF DR. AUG. WEISMANN'S PAPER ON "THE 

 SEASONAL-DIMORPHISM OF BUTTERFLIES." 



[LEIPZIG, 1875, PUBLISHED BY W. ENGELMANN.] 



To which is Appended a Statement of Some Experiments made upon 



Papilio Ajax. 



BY W. H. EDWARDS, COALBURGH, \V. VA. 



Dr. Weismann has lately published an account of certain experiments 

 made by him during a course of years with a view to determine the facts 

 relating to seasonal-dimorphism, and from them to deduce the reasons for 

 the phenomena. As several North American butterflies are thus 

 dimorphic, I have thought that the substance of Dr. Weismann's paper 

 would be interesting to the readers of the Entomologist, it being too 

 long to print in full. I have therefore written out the following abstract, 

 following as closely as possible the language of the author. I have added 

 a statement of my own experiments with Papilio ajax, the results of which 

 confirm the theory advanced by Dr. Weismann as to the causes of the 

 phenomena in question. 



The phenomena of seasonal-dimorphism had been known for a long 

 time, and had been established in the case of Vanessa prorsa and levana 

 early in this century, prorsa being the summer, Iroana the winter form. 

 Prof. Zeller ascertained that Lycaena amyniula and L. polyspcrchon were 

 summer and winter forms of one species. Dr. Staudinger found Antho- 

 charis belia and ausonia to have the same relationship. On his interest 

 being excited by these cases, the author instituted experiments. At first 

 he supposed that the difference in the butterflies might be of a secondary 

 nature, having its foundation in the difference of the larvae, which might 

 be owing to the difference in the food plants of the winter and summer 

 broods. But the most strongly dimorphic butterfly, levana, feeds on one 

 plant only, Urtica major, and although the larvae show a pronounced 

 dimorphism, the two forms do not alternate with each other, but make 

 their appearance in every generation. He then experimented on the 

 indirect influence of the seasons, but concluded that the cause of the 

 phenomena did not lie here. It must then lie in the direct influence of 

 changing outward conditions of life, those in the winter generation being 

 undoubtedly different from those of the summer generation. There are 



