The natural order, _Cossi_, of which the larva and pupa have been already described, contains but ten genera, even including those whose claim to a place in the order is somewhat doubtful; and these ten are readily referable to six families. The genus, Stygia, of New Holland, seems from Latreille's description, decidedly to belong to this order. Speaking of Stygia Australis, he says, "_M. Villiers la considère comme intermediare entre les Sesies et les Zygènes; mais elle n'a point de trompe; ses palpes sont ceux de Cossus; ses antennes sont courtes, et nullement en fuse, et plus analogues a celles de certains Bombyx qu'a celles des Sesies et des Zygènes_."[57] Now the fact, as M. Latreille supposes, of having no antlia, argues most forcibly the impossibility of uniting this genus either with Sphinx or Zygæna; for the sub-class Sphinx not only possesses the most elongate and conspicuous antlia of any sub-class, but retains this character to its very circumference, and imparts it to approaching groups, whose types will be found entirely aglossate: its similarity therefore in shape to the Sesiæ, which tribe is generally understood to include the Ægeriæ, is merely that relation of imago which I have before so repeatedly pointed out. The situation, which without this genus must have been vacant, thus filled, gives us a most perfect chain of families throughout the order, except at the point of connexion with Phalæna, a point of no consequence, because it too much favours old theories to be contested. [57] Règne Animal, tom. V. p. 395. It is rather remarkable, that in this order no instance should occur of more than three genera belonging to any one family, a number which I should hardly suppose complete, because a difficulty must always occur in placing, as in discovering the typical genus or species, where the number is confined to three. The introduction of a new generic name, after what has been said on that subject, may appear rather an inconsistency, but I found it indispensable, as the species in question would not bend to either of the established genera, Trochilium or Ægeria; it will, moreover, afford those whose labours in this way I have somewhat deprecated, a fair opportunity for retaliation. The families and their relative situations, as far as my immature and hastily-formed judgment will allow me to decide, I have shown in the annexed diagram: but it is now time for me to describe the species whose situation I am endeavouring to point out. Sub-kingdom, INSECTA. Characters from the imago. The body is divided into three parts, head, thorax, and abdomen; the head has two fixed compound eyes, and two moveable antennæ. Insects have six jointed legs in pairs; they breathe by lateral spiracles. Class, LEPIDOPTERA. Characters from larva, pupa, and imago. Larva polypod, bears no resemblance to the imago; pupa quiescent, bears no resemblance to the imago. Imago has four scaly wings, and the mouth aglossate or antliate.