THE CANADIAN ENTOMOLOGIST. 221 



A SUMMER WITH CHRYSOPHANUS DORCAS, KIRBY. 



BY WILLIAM W. NEWCOMB, M. D., DETROIT, MICH. 



Chrysophanus dorcas is a very interesting little butteifly for several 

 reasons : its boreal origin, in southern Michigan, confined as it is to 

 .certain detached islands or areas of decided northern character, wherein its 

 food-plant occurs, its unworked life-history, its supposed rarity and little 

 known distribution, all have made it an attractive field for investigation. 

 It is also worth while to note the confusion which attaches to its identity, 

 two other distinct species, efiixanthe and helfoides, having been mistaken 

 for it. 



Scattered throughout Southern Michigan, along the borders of 

 streams, in the vicinity of lakes and in other low wet places, are numerous 

 peat bogs, in which the vegetation is of a different type from the 

 surrounding growth. I can here simply call attention to the existence of 

 these northern bog areas in a region of more pronounced southern aspect. 

 Certain boreal insects, among them Chrysophanus dorcas, occur in this 

 latitude only in these peculiar bog habitats.* 



Oakland county, one of the counties of south-eastern Michigan, is full 

 of little lakes ranging in size from an acre or two to several square miles. 

 It is particularly rich in the number and variety of the bog areas which it 

 contains, and consequently many of the bog plants of the north occur 

 abundantly. Among them there is one, the shrubby cinquefoil (Dasiphora 

 fruticosa), with which we are particularly concerned. Doubtless the 

 conditions necessary for the continued existence of this plant in this 

 latitude are unusually favourable in the bogs of this county. Invariably 

 around the pretty yellow flowers of the cinquefoil bushes at the proper 

 time of the year, July, are to be found the little butterflies of dorcas. 



The particular place where most of the observations upon this insect 

 were made was in the Bloomfield Hills region, about twenty-four miles 

 from Detroit. It was chosen because it was the nearest spot to the city 

 where a goodly amount of the cinquefoil grew, and because of its accessi- 

 bility. The country about is diversified by low hills and little valleys, and 

 a small stream, a branch of the River Rouge, arising in the lakes to thei 

 westward, flows through the locality. There is considerable low, wet 

 ground about the borders of the stream, and within half a mile to the 



*See Edgar N. Transeau : The Bogs and Bog Flora of the Huron River 

 Valley: Botanical Gazette, 40: 351-375, 418-448, and 41: 17-42. On the 

 Geographic Distribution and Ecological Relations of the Bog Plant Societies of 

 North America : Bot. Gaz., 36 : 401-420, 

 July. 1909 



