The genus _Argynnis_ is one of the largest genera of the brush-footed butterflies. It is well represented in Europe and in the temperate regions of Asia, some magnificent species being found in the Himalayas and in China and Japan. It even extends to Australia, and recently two species have been discovered in the vicinity of the great volcanic peak, Kilima-Njaro, in Africa. But it has found its greatest development upon the continent of North America. The species composing this genus are among our most beautiful butterflies. Owing to the fact that there is a great tendency in many of the forms closely to approximate one another, the accurate distinction of many of the species has troubled naturalists, and it is quite probable that some of the so-called species will ultimately be discovered to be merely local races or varietal forms. The species that are found in the eastern part of the United States have been studied very carefully, and their life-history has been worked out so thoroughly that little difficulty is found in accurately determining them. The greatest perplexity occurs in connection with those species which are found in the region of the Rocky Mountains. While silvery spots are characteristic of the under side of most of the fritillaries, in some species the silvery spots are not found; in others they are more or less evanescent, occurring in the case of some individuals, and being absent in the case of others. (1) =Argynnis idalia=, Drury, Plate X, Fig. 3, ♀; Plate V, Fig. 4, _chrysalis_ (The Regal Fritillary). _Butterfly._--The upper side of the fore wings of the male is bright fulvous, marked very much as in other species of the genus. The upper side of the hind wings is black, glossed with blue, having a marginal row of fulvous and a submarginal row of cream-colored spots. On the under side the fore wings are fulvous, with a marginal row of silver crescents, and some silvery spots on and near the costa. The hind wings are dark olive-brown, marked with three rows of large irregular spots of a dull greenish-silvery color. The female is at once distinguished from the male by having the marginal row of spots on the hind wings cream-colored, like the submarginal row, and by the presence of a similar row of light spots on the fore wings. Expanse, 2.75-4.00 inches. _Egg._--The egg in form is like those of other species of _Argynnis_. _Caterpillar._--The caterpillar moults five times before attaining to maturity. When fully developed it is 1.75 inches long, black, banded and striped with ochreous and orange-red, and adorned with six rows of fleshy spines surmounted by several black bristles. The spines composing the two dorsal rows are white, tipped with black; those on the sides black, tinted with orange at the point where they join the body. The caterpillar feeds on violets, and is nocturnal in its habits.