According to the manner in which they have been respectively constituted, _Callidryas_ therefore is best distinguished from Colias by the antennæ, which in the latter terminate in an obconical club; and from _Rhodocera_ (including _Gonopteryx_ of Dr. Leach), which has these organs likewise truncated, by the shape of the wings, which never present acute angular projections. The prevailing colour of the species is yellow, from deep orange to the palest sulphur yellow. The females are usually of a paler hue than the males, and the sexual differences are strongly marked in other particulars. On the under side of the wings there are almost invariably one or two small spots, near the middle, of a silvery or rusty-brown hue; these are either wanting or very minute in the males, while they are distinctly marked in the females. The former sex, in the majority of species, presents a very peculiar character in having the anterior edge of the under wings provided with a kind of pulverulent glandular sac, which varies much in size and colour in different species. A great similarity prevails among the different species of _Callidryas_, and they are consequently difficult to determine. They inhabit the intertropical regions of the two continents. CALLIDRYAS EUBULE. PLATE VIII. Fig. 1. Pap. Eubule, _Linn. Cramer_, Pl. 120, F, C.--Caterpillar, _Stoll’s Supp. to Cramer_, Pl. 3, fig. 1, A.--Callidryas Eubule, _Boisd. Species general_, i. 613. This insect so closely resembles _C. Marcellina_ that it is possible they would still have continued to be confounded, as they were by the earlier entomologists, had not the different appearance of the caterpillar indicated their essential distinction. In the male the surface of the wings is a fine citron-yellow, with a narrow border of a deeper hue; the fringe of all the wings marked at remote intervals with small rust-coloured spots. Beneath the colour is red, or brownish-yellow; the upper wings with a double ferruginous spot at the extremity of the discoidal cell, and a brownish zig-zag ray towards the outer margin; the under wings likewise with two rounded discoidal spots, silvery in the centre, and surrounded by a rust-coloured ring; there are likewise several undulating brown lines running across the surface more or less distinctly defined. The female is bright yellow inclining to orange, the inferior wings much rounded, and having an orange-coloured fringe interrupted with transverse brown stripes. The position and appearance of the discoidal spots similar to what has been described in the male: the under side deep ochre yellow. Body yellow, with greenish hairs on the thorax; antennæ, and terminal joint of the palpi, rose-colour mixed with brown. [Illustration: PLATE 8. 1. _Callidryus Eubule with Cater. & Chrysalis._ Brazil. 4. _Terias Mexico._ Mexico. _Lizars sc._]