32 Canadian Record of Science. 



All these butterflies have at least two broods in the 

 .season, otherwise dimorphism could never develop, and 

 in the allied species, such, as Gracilis and Faunus, which 

 .are single brooded or monogoneutic, it does not occur. 



These forms were all formerly thought to be distinct 

 species and were so named, and it was only by careful 

 observations and breeding from the egg that their inter- 

 esting relationship was discovered. 



Among this group, the most curious case is that of 

 Orapta Interrogationis, as it not only differs in colour but 

 also in the shape of the wings, and even in certain 

 structural features. 



In most of these cases the dimorphism is largely 

 seasonal, one form being the autumnal form, which 

 hibernates and appears again in the spring, and the other 

 tbe summer form produced from the hibernators, but the 

 separation is not complete, as a few of the summer brood 

 .are of the autumnal type. 



But by far the most startling instance of dimorphism, 

 on this continent at least, if not in the world, is that 

 which has been recently worked out by Mr. David Bruce 

 .and Mr. W. H. Edwards, to the latter of whom we owe 

 most of our knowledge not only of the dimorphism and 

 polymorphism of our butterflies but also of their prepara- 

 tory stages, and who stands at the head of North American 

 Lepidopterists. 



The case to which I refer, is the discovery that Papilio 

 Oregonia, a form of yellow swallowtail, and Papilio Bairdii, 

 a form of black swallowtail, are merely dimorphic forms 

 oi one species, in spite of belonging to two distinct sub- 

 groups of the genus Papilio. 



So incredible did this seem that some of us found fault 

 with Mr. Edwards for his first announcement, as we 

 (thought the evidence not perfectly conclusive, so Mr. 

 Edwards, thougli a man of 72 years of age, went out to 



