230 THE CANADIAN ENTOMOLOGIST. 



If there was no error in getting the eggs, such as overlooking eggs 

 that had been laid on the plant before the female was tied to it, then there 

 could be no question of dimorphism, for the eggs that I received were 

 mailed the day they were laid, so that there was no opportunity for any 

 mixing up of larvse. As Mr, Bruce is an entomologist of many years' 

 experience, and had, as he assured me, taken the utmost care in these 

 experiments, knowing their importance, the flicts showed dimorphism, and 

 of a remarkable sort. There was nothing like it in the North American 

 butterfly fauna. 



Mr. Bruce's visits to Glenwood Springs began in i8S8, and from the 

 first he had noticed that Bairdii and Oregonia were always associated, 

 and in about equal numbers. But it was a long time before he discovered 

 the food plant. Some one brought him a green, black-striped caterpillar, 

 taken on Artemisia dracunculoides, which looked like an Asterias in its 

 last stage. From the pupa produced came a Bairdii imago. Then he 

 began to get eggs by confining the females over the Artemisia. It seems 

 a strange food for one of the Asterias or Machaon groups; all the known 

 species, except P. Indra (that is to say, all the species whose larvte are 

 known), feeding on Umbellifene, fennel, carrots, and the like. Artemisia 

 belongs to the Composite. It is true the larvae of the Papilios I am treat- 

 ing of will eat carrot, parsnip and fennel in confinement, but not willingly, 

 and both Mr. Bruce and myself, also Mrs. Peart, have found the mortality 

 excessive when feeding on those plants. There were large fields of carrots 

 about the Springs, and we inquired of several of the owners if they had 

 ever noticed the green caterpillars, but found no one who had done so. 

 The Artemisia grows everywhere in the valley of Grand River and its 

 tributaries, and often covers the ground over large areas. It stands about 

 three feet high : a loose, open-growing plant, with many long stems 

 shooting up from the base, or branching at a small angle from the main 

 stem, and these bear very small leaves. One can look through a large 

 clump of it and a caterpillar of the Papilios could not easily escape obser- 

 vation. The yellow eggs, too, are in strong contrast with the peculiar 

 gray-green of the leaves, and would easily be seen. 



Mr. Bruce has never caught the two forms in copulation, though he 

 seemed to miss it more than once by a very little. He had written me 

 that on one occasion he saw an Oregonia ? pursued by two males same, 

 and also by three males Bairdii, rolling through the air like a ball, and so 

 low down that he made effort to catch them all with a throw of his net ; 



