Again, on the subjects of orders, a term I have already been induced to use now and then, I am quite aware that I here am guilty of another misdemeanour, and more especially as I call them natural orders, meaning thereby orders among the contents of which nature has established the similarity; and to the formation of which "the cunningly devised fables" of man have contributed but very little; and meaning also that nature has implanted in us all, more or less, the power of distinguishing such orders by a mere glance, and without any reference to our books.
Furthermore, the naming of orders which I have been obliged to mention by name, in the unscientific way which I have adopted, merely making them plurals of established names, of large and overgrown genera, I acknowledge to be a confession of ignorance not usual in this our day, especially as these old genera have almost in every instance the disadvantage of being euphonious, easily pronounced, expressive, and universally understood; and an opportunity once missed of coining names for three hundred new orders, (and each might have been a combination of consonants which no one could spell, or speak, or read, or understand,) alas! alas! may never occur again.
To return; I suppose the sub-class Phalæna to contain seven natural orders, a number precisely similar to that discovered from observations made on the larva by that most accurate and indefatigable naturalist, Dr. Horsfield;[43] and I may add, my own divisions are derived from the same source, together with the pupa and whole habit: the perfect insect has no characters, hitherto discovered, by which we can ascertain either sub-class or order, and from this circumstance I am compelled to omit those genera of whose larvæ I am ignorant,[44] and even to leave those as doubtful, of which I possess but a partial knowledge of that state.
Natural Order—Bombyces. Has an elongate cylindrical downy larva, which rolls itself into a ring when touched; the pupa changes in a close gummy oval cocoon, remarkably small for the size of the imago. Among the exotic species of Lasciocampa, we find in the males particularly slender bodies, expansive wings, the inferior grooved to receive the abdomen, and diurnal flight, all of them characters so indicative of an approach to Papilio, that we scarcely hesitate a moment in assigning it the approaching station, not but I expect fully that time will eventually furnish us with a connexion on each side yet more conclusive.[45] The second genus of Bombyces is probably Odenestis, and the third Gastropacha, whose prominent and elongated palpi appear to point out an approach toward a tribe of insects with the same peculiarity, of which there are several to be found in the following order:
Natural Order—Cossi. The larva is depressed; naked, except a very few scattered hairs; has sixteen feet; lives through one or more winters; never rolls itself in a ring when touched; feeds on the solid interior woody parts of vegetables. The pupa generally changes in a tough oval cocoon, interwoven with particles of its food. It has a double ring of raised denticulations of each segment of the abdomen, by means of which it is endowed with a considerable power of locomotion. The genus Zeuzera is very near the point of contact with the Bombyces. In Zeuzera there is much resemblance to the antennæ of Gastropacha. One genus, or group of genera, I expect will prove to be Stygia, a native of New-Holland. A second, at the point of contact with Sesia in Sphinx, must be Ægeria; thus retaining its place among British insects, immediately between Sesia and Cossus.[46] This is the first of a series of the most beautiful instances of approach, or rather, of what ought to be termed relations of analogy, that any system has ever previously disclosed. As a few words will again be necessary on this subject, I refrain from any further observation here, than merely requesting the reader to examine how minutely the Sphinx characters are appropriated by a true lignivorous Phalæna, which cannot be said, in any of its prior and principal states, to have the most distant approach to Sphinx. A third genus is, probably, the strange and paradoxical exotic Oiketicos, which has been minutely described in the Linnæan Transactions; and a fourth is Hepialus.[47] This genus has some slight points in which it differs from the others of the order already known, the larva being radicivorous only, seldom or never ascending internally the stems of plants: it changes in the earth.
Natural Order—Notodontæ. The larva is naked, has sixteen feet, and is, in different genera, furnished with excrescences, and apparent distortions in various parts of the body. The eighth or last pair of feet, and three last segments of the abdomen, are elevated; when the insect is at rest, the head and first segment are raised in a similar manner. In one genus (containing Camelina) the head and extremity of the abdomen nearly meet over the back, when raised in this singular manner. The posterior feet are frequently useless in walking; in some genera, entirely obsolete. The pupa is smooth, in a cocoon, mostly among dead leaves on the surface of the ground: sometimes it is glutinous, and interspersed with fragments of wood, like the last. I confess I am exceedingly puzzled both with the contents and extent of this order; but this arises from my having seen so few of the species in the larva state. Ptilophora plumigera, figured by Mr. Curtis,[48] I had always considered a Notodonta; but the larva evidently excludes it from the order, and, I should imagine, places it among the Noctuæ; where among them I know not, for I have not the slightest idea of any congeners, either of the larva or imago. The larva from which a collector of Lepidoptera could expect to obtain such an imago would be unicolourous, stouter in the middle, elevated in the penultimate segment, and more attenuated towards the head.[49] Pygæra appears doubtful at first, but when observed quite at rest, and in a perfectly natural position, elevates the head and tail, though in a much less degree than the typical genus. Mr. Curtis's genus Notodonta contains several good species, which may be considered as typing the order, as Ziczac, Tremula, and Dictæoides. The first species, Trepida (the Peridea serrata of Mr. Stephens,) seems more nearly related to Endromis. Both these may, however, probably belong to the order Notodontæ, and be situate near the approach to the central order Phalænæ. Petasia cassinea and Episema cærleocephala appear to be genuine Noctuæ, and very near Chareas graminis, and Rusina ferruginea, as far as my very imperfect knowledge of these four species will allow me to judge. Clostera is another departure from the type; but this may be accounted for, in some degree, by its close proximity to Hepialus, from which genus it borrows its remarkably short antennæ, and other peculiarities. It seems a strange perversion of judgment to place Platypteryx at the end of or among the Geometræ; but Linnæus did so, and that is enough. Hubner, Haworth, and a few others, positively ventured, in this glaring instance, to refer this genus to the Bombyces; but their ideas were thought to be wrong, and their judgment was, nem. con. reversed. I have elsewhere expressed a wish that my readers should convince themselves, and the frequent occurrence of the larvæ of Platypteryx and Cerura would afford any naturalist abundant opportunity of ascertaining, that they can be referred to but one order. The approach of Platypteryx and Cilix to the Pyralides, in assuming so much of their characters, is very interesting, and is a most striking departure from the typical form. These genera also approach the Lithosiæ, but not so nearly as some exotics.
Natural Order—Lithosiæ. The difference between Lithosiæ and Arctiæ is rather difficult to point out; yet a difference exists, which it is perfectly impossible not to detect. The larva of Lithosiæ has sixteen feet, is very active, is moderately hairy, does not readily roll itself in ring, but occasionally assumes that attitude. The pupa is smooth, changes in a slight web, in which the hairs are intermixed. The approach of Lithosia[50] to the genus Yponomeuta, in Tinea, scarcely need be pointed out. It will be observed, that Mr. Samouelle[51] was aware of this approach, and placed the genera Lithosia and Yponomeuta following each other. The splendid Callimorpha dominula, although, to all appearance, a real Arctia, must be included in this order, and placed in contact with the following one.
Natural Order—Arctiæ. Larva, with sixteen feet, generally very hairy, bear-like; rolls itself in a ring when touched; pupa smooth, in a slight web. Whether the whole of Mr. Curtis's genus Acronycta must be included in this order, I am not able positively to say: the genus Apatela of Mr. Stephens certainly must, and until I have obtained sufficient information to decide on Acronycta, we must bring Mr. Stephens's genus only into the order, leaving the remainder of the species undisposed of. The development of the antlia in Acronycta discovers as near an approach to Noctua, as Lithosia does to Tinea; but the bear-like, cocoon-spinning larva place these insects in close alliance with the true Arctiæ.
Natural Order—Lariæ. Larva, with sixteen feet, and furnished with various brushes, or fascicles of hair, on different parts of the body, but mostly on the anterior dorsal segments; it rolls itself in a ring when touched. The genus Porthesia of Mr. Stephens may be considered a near approach to Eriogaster, in the following order, Bombyces, in many of its peculiarities, as the abdominal hair with which it covers its eggs, in its antennæ, &c. Orgyia antiqua, on the other hand, is in habit, expansion of wing, slender body, and apterous female, a close approach to the Geometræ, near the genera Hybernia and Nyssia; in fact, were it not for the larva, that is, were the larva unknown, we should have no hesitation about placing this insect with the Geometræ.
Natural Order—Phalænæ. Larva, with sixteen feet; it has a circle of wart-like protuberances on each segment, from each of which spring a few strong bristles; pupa, smooth, with a few bristles at the tail; changes in a cocoon, which is singularly left partly open at one end. We have but one species of this order in Britain, Saturnia carpini;[52] but among exotics there is a great variety, some remarkable for the immense expanse of their wings.[53] Probably Phalæna Atlas of Linnæus is the centre of the group, and, if so, the centre and type of the class Lepidoptera.