106 THE BIOLOGICAL REVIEW. 



base line, which lies to the north of the South Saskatchewan, 

 and as far west as the cactus hills, and there can be little 

 doubt that the range of P. Columbia nokomis is coterminous with 

 the range of this food plant E. argentea. 



The food plants of the southern form (P. Columbia) in 

 Ontario, Quebec and in the State of Maine, so far fairly well 

 identified, are Prunus virginiana, Prunus pennsylvanica, Nemo- 

 panthes canadensis, Kalmia augstifolia, Rhodora canadensis, 

 Salix sp., Abies nigra, Larix americana. None of these are allied 

 botanically to E. argentea, but I think it most likely that the 

 larvae would take very kindly to the leaves of our common 

 Shepherdia canadensis. 



On comparing a seiies of specimens of Columbia with 

 Columbia nokomis — the Manitoba form — the difference is very 

 obvious in the brighter colors and more sharply defined color 

 areas. This difference may be in some measure from a differ- 

 ence of food, or from the much longer duration of daylight while 

 the larva? are feeding, or perhaps in part from the lower tem- 

 perature in winter. And perhaps it may yet be shown that the 

 north and north-west territories are the normal habitat and 

 nokomis the normal form of the species, differentiated ages ago 

 from cecropia by climatical and other conditions, and that the 

 now southern form is from degenerate stragglers from the north. 



The following points of difference may be noted between the 

 Columbia nokomis form and the Columbia form, as represented by 

 Ontario specimens, and as compared with Smith's description of 

 Columbia, parts of which are given in brackets. The standard 

 of color is Ridgway's Nomenclature of Colors. 



Antennae, central shaft, bright reddish brown ; pectinations, 

 darker (black) ; palpi, light liver brown (dark maroon brown) ; 

 dorsum of thorax, bright reddish liver brown, with a posterior 

 pure white band (dark maroon with a short, grey band) ; under 

 side of thorax, reddish liver brown (black) ; legs, reddish brown,, 

 pile darker (black, slightly tinged with brownish) ; abdomen, 

 with alternate annulations, bright liver brown and pure white 

 (black and dirty white). 



Primaries, above, with a rather sharply elbowed pure white 



