CHIONOBAS 1. 
to whose zeal and skill lepidopterists owe the discovery of several new species 
of Californian butterflies, and a better acquaintance with many rare ones. Mr. 
Behrens wrote, 26th June, 1873: “I caught seven of the large Chionobas in 
Mendocino County. It seems to be a very local species, and confined to high 
ridges in the depth of the red-wood forest. They would alight on a hot, sandy 
spot, or on a fallen tree, or on the fresh leaves of young oak trees, always in the 
heat of the sun. Fallen trees and dense thicket make the chase for them difficult. 
They are very vigilant and shy, but will return to a spot they have once visited, 
though for a short hour of the day only, either earlier or later, according to the 
state of the atmosphere and wind, and when tired from their usual high, rapid 
flight. Water and moisture do not seem to attract them. They should be 
looked for in the month of May, as soon after they become shattered. It is 
almost impossible to obtain a perfect specimen later.” 
Iduna is one of the largest known species of Chionobas, rather surpassing even 
Gigas, Butler. These two form a sub-group, separated by no wide interval from 
Nemdensis , Felder, and Californica, Boisduval. The several species of this 
genus are mostly alpine or boreal, Iduna and Gigas apparently being the excep¬ 
tions, the former living upon ridges of moderate elevation, and Gigas being 
taken at quite low levels. Three other species, Chryxus, Uhleri, and Semidea , 
inhabit the mountains of Colorado, and of these Chryxus is taken in California 
and at Hudson’s Bay ( Calais , Scudder, proving to be the female of this species), 
and Semidea abundantly on the summits of the White Mountains, New Hamp¬ 
shire. Over the most northern portions of the Continent still other species of 
Chionobas are found, and of these all seem to inhabit corresponding parts of 
Europe and Asia. 
Iduna may readily be distinguished from Gigas. It has less curvature of 
costal margin of primaries, and much less rounded hind margin ; the same wing is 
also more produced, or pointed apically; the ocelli are differently arranged, those 
of Iduna being set in a straight line, of Gigas irregularly, the small ocellus of 
first median interspace lying outside a straight line connecting the larger. This 
peculiarity is observable in the two females in my own collection, and also in the 
unique male in British Museum collection, as mentioned by Mr. Butler, who first 
directed my attention to this peculiarity of the species. On the under side, the 
outer edge of the discal band in Gigas is scolloped from margin to margin ; in 
Iduna it is not scolloped, but irregular. These differences may be seen by refer¬ 
ence to the Plate, and they are constant in all the individuals of either species 
at present known in collections. 
