_Under Side._ The anterior wings, next the body, are of a faint dark red, with many spots and marks of a dirty olive, differently shaped, margined with white. An orange margin runs along the exterior edge, intersected by the blue tendons; and above it are several triangular marks of a faint orange, on a blueish hazel ground, which deadens as it approaches the margin. The posterior wings have on each a white band, running transversely, and meeting just below the extremity of the body; within which, and including the anal groove, are many round, oval, and other shaped marks of chocolate and dark olive; verged with white. A scolloped margin, of a deep lemon colour, runs along the posterior edges, verged with dirty green, and separated from the white band by a bar of hazel colour, and some large brown reddish spots and marks. Two blue spots are placed just above the two longest tails, with several lesser ones, just above the lemon-coloured margin. I have thought it more in accordance with the principles which are now almost universally adopted, in regulating specific nomenclature, to revert to the original Linnæan {2}name of Jason in preference to that of Fabricius. This butterfly may be regarded as one of the most splendid of the Lepidoptera of Europe, to the southern portion of which and to the northern shores of Africa it appears to be confined. The strength of its general structure indicates great powers of flight, and we accordingly find that it is able to sustain itself in the air with very little motion of the wings. The female differs from the male only by having the centre of the posterior wings adorned with small blue spots on the upper side. There are two broods in the year, namely in June and September, and, according to M. De Villiers, the insect emits a strong scent of musk. The caterpillar is naked and thickened in the middle of the body; the tail tapering into two short points, the head is also armed with two conical erect horns. In this respect, therefore, this insect very nearly approaches the genus Apatura, of which the purple Emperor, Ap. Iris is the type, thus proving the advantages to be obtained, in studying the natural relations of this difficult order of Annulosa, from an accurate acquaintance with the structure and habits of the early stages of the insect. There are several species, having the same general form as the Jason, including Athamas, pl. 2. fig. 3. 4; Eudoxus, vol. iii. pl. 33. f. 1. 4; Camulus, vol. iii. pl. 30. f. 1. 2. Mr. Swainson has, accordingly, formed them into a distinct group, to which he has given the name of Jasia, in pursuance with his customary, but scarcely correct plan, of raising the specific name of the typical species into a generic name, and then giving a new specific name to such type. M. Boisduval, rejecting this system of nomenclature, has more recently proposed for the same group the name of Charaxes, which I have adopted.