The present generic group was first separated from Papilio by Dr. Boisduval. None of its characters, taken singly, are very strongly marked, but their aggregate importance is sufficiently considerable to authorise its adoption. As in Papilio the antennÆ form an elongate club, having the extremity slightly curved upwards, the palpi are longer than in the genus just named, but they never rise above the forehead. The prothorax is much developed anteriorly, and forms a pretty distinct neck. The abdomen is long and robust, that of the male deeply grooved on the under side, and provided at the anal extremity with two large rounded valves. The wings are large, of a strong texture, and furnished with salient nervures; the anterior pair elongate; the posterior with wide shallow indentations, and never prolonged into a tail.

We are very imperfectly acquainted with the natural history of the insects of this group in their early stages. Their remote localities, and the rarity of most of the species, have, for the most part, prevented them from falling under the notice of competent observers. The caterpillar and metamorphoses of one of them (O. Heliacon), however, have been described by Dr. Horsfield. Like the caterpillars of Papilio, it is furnished with two retractile tentacula; the body is large and thick, and bears eight rows of rather long fleshy prominences, of a conical shape. The chrysalis into which it is transformed is somewhat curved, having the head obtuse, and a few projecting points above the middle. It is suspended by the tail, and a transverse band, which, however, does not encompass the body, but is inserted on each side. (See Fig.)

This group is but of limited extent, but it comprehends some of the largest and most beautiful lepidoptera yet known to us. With one exception, which extends over a portion of the Indian continent, they are confined to the Mollucca, Philippine, and others of the numerous and extensive islands of the Indian Archipelago. The species figured, which is the most beautiful of the whole, and to which LinnÆus applies the epithet of august, has been long known and highly prized by collectors. It is named

ORNITHOPTERA PRIAMUS.
PLATE 1. Fig. 1.

Such a remarkable discrepancy exists in the appearance of the sexes, that they were always regarded as separate species till lately, when their proper relationship to each other happened to be ascertained. The anterior wings of the male are deep velvety black, with two broad longitudinal stripes of rich silky green, curved, and narrowing at both extremities; between these stripes there is a large brownish spot disposed longitudinally. The hinder wings are silky green, with the posterior margin, and a series of four pretty large circular spots, velvet-black; between the black spots and posterior border are two orange spots, and another of larger size towards the base of the wing. On the under side, the anterior wings have a macular band of gilded green, formed of contiguous wedge-shaped spots, an irregular patch towards the centre, and two streaks near the apex. The under side of the hinder wings corresponds to the surface, but the green is of a more golden hue, and the circular spots larger, and seven in number. The antennÆ, head, and thorax, black—the latter with a central line and two posterior spots of golden green; breast spotted with red on the sides; abdomen bright yellow.

The female is considerably larger, frequently measuring nearly eight inches between the tips of the wings. The prevailing colour is dark brown, deepening towards the extremities of the wings; the upper pair traversed by a macular band of impure white, the spots unequal and generally interrupted or notched; the hinder pair having a curved row of six large wedge-shaped spots behind, of a whitish colour powdered with black, the base tinged with yellow, and each with an orbicular black spot in the centre. Head and thorax entirely black, the abdomen whitish yellow above and deep yellow beneath.

Varieties of both sexes have occurred, for there seems little reason to doubt that the insect figured by Guerin (Voyage de la Coquille, Ins., pl. 13, fig. 1 and 2) under the name of P. urvillianus, is a variety of the male, while a female variety is described by Boisduval28. In the former, the green of the superior wings is replaced by violet-blue of a very brilliant tint, and in the hinder part that colour runs in a broad stripe along the nervures, dilating considerably towards the posterior margin. This example was found at Offack.

The Priam butterfly is found in the islands of Amboina, Rawack, and Ceram. It has been observed to hover about the Mangifera Indica in preference to other trees, and it has hence been conjectured that it deposits its eggs on the leaves, and that they constitute the food of the caterpillar. It never occurs in large numbers, and is hence somewhat rare in collections. Specimens of both sexes are preserved in the valuable collection of insects belonging to the Edinburgh University Museum.

ORNITHOPTERA REMUS.
PLATE 1. Fig. 2.

One of the largest species, the expansion of the wings sometimes measuring nearly eight inches. The superior pair are black, with a slight greenish reflection, and having a broad greyish-white stripe running along each side of the secondary nervures. The inferior wings are dark grey on the surface, and of a shining white on the under side, the latter having a black sinuated border interrupted by seven irregular spots of golden-yellow diminishing in size as they approach the abdominal margin. In the female, which is the sex represented on the adjoining plate, the golden-yellow spots are much larger, somewhat wedge-shaped, and each of them, except the outermost, marked with a large oval black spot. The abdomen is bright yellow above, paler on the under side, and irregularly spotted with black; the head, thorax, breast, and antennÆ entirely of the latter colour.

The native country of this elegant species is the island of Amboina.