The genus to which we have assigned the above name has been hitherto blended with the _Uraniæ_. It is doubtless very closely connected with these insects; but the differences both in the appearance of the perfect insects and the respective caterpillars, render it expedient that they should be separated. The character by which it and _Urania_ are widely separated from all others, is the form of the antennæ, which are filiform nearly to the middle, where they thicken a little, and from that gradually narrow to a point. The palpi are lengthened and slender, having the second joint greatly compressed, the terminal one more slender, nearly cylindrical, and naked. There is no closed discoidal cell in any of the wings, and almost all the nervures diverge from the base. Not many different kinds are known, and, with one exception, they are natives of America and the West Indian Islands. Their splendid tints of golden green arranged in transverse bars, render them perhaps the most chastely beautiful insects that exist, and has caused them to be named Emerald Butterflies in this country. Sometimes also they are called _Pages_. They fly so high in the air and with so much velocity, that it is nearly impossible, Madam Merian informs us, to catch them, and the only way therefore to obtain good specimens, is to feed the caterpillar. “Great numbers of this insect,” says Mr. Swainson, speaking of a species almost the exact counterpart of _U. Leilus_, “were flying during the whole of the morning, past _Aqua Fria_ (Pernambuco) in a direction from north to south: not one deviated from this course, notwithstanding the flowers which were growing around: they flew against the wind, which blew rather strong, and near the ground, but mounted over every tree or other high object which lay in their course; yet their flight was so rapid, that I could not capture a single specimen. They went singly, and near fifty or sixty must have passed the spot opposite the window before mid-day: they continued to pass for three or four days in this manner. 12th June 1817[37].” The present genus differs from Urania in the perfect insect having three distinct tails at the hinder extremity of the posterior wings; neither are these wings so much elongated as in the group just named. The differences between them in their early states will be seen by comparing the following descriptions. [Illustration: PLATE 28. _Lizars sc._ _Thaliura Rhipheus._ Madagascar.] THALIURA RHIPHEUS. PLATE XXVIII. Pap. E. A. Rhipheus, _Fabr._--Pap. Rhipheus, _Cramer_, Pl. 385, fig. A, B.--_Boisduval, Nouvel. Annal. du Museum d’His. Nat._ p. 260, Pl. 8, fig. 1, 2.