MacLeay.
| Mandibulata. | Haustellata. |
| Trichoptera | Lepidoptera |
| Hymenoptera | Diptera |
| Coleoptera | Aptera |
| Orthoptera | Hemiptera |
| Neuroptera | Homoptera. |
| K. and S. | |
| Coleoptera | Hemiptera Leach |
| Orthoptera | Homoptera Leach |
| Neuroptera | Lepidoptera |
| Hymenoptera | Diptera. |
In these two last columns, you see, I differ little from M. Savigny: I merely exclude the Aphaniptera as forming an osculant Order, and I have added the Coleoptera and Heteropterous Hemiptera for reasons I shall soon assign. From Mr. MacLeay I differ more widely, which has resulted from our different ideas as to the mode of tracing analogies; his theory leading him to the metamorphosis, and mine leading me[1293] to the perfect insect, for the foundation of our several systems. It remains that I show how each of the pairs in my columns represent each other: but I must observe, that the analogies exhibited by insects in the corresponding Orders of these columns are not equally striking in all their respective members; but only in certain individual species or genera, more or less numerous, by which the nearest approach is made to the contrasted forms.
To begin with the Coleoptera and Heteropterous Hemiptera.—Both are distinguished by having an ample prothorax, a conspicuous scutellum, the neuration of their wings, the substance of the hard part of their hemelytra, which, as in Coleoptera, sometimes imitates horn and sometimes leather, and is occasionally, like elytra, lined with a hypoderma[1294]; the articulation of the head with the trunk is likewise the same in both[1295]: and some Heteropterous species so strikingly resemble beetles (Lygæus, brevipennis &c.), having little or no membrane at the end of their hemelytra, that they might easily be mistaken for them. These circumstances prove, I think, that this suborder is more analogous to the Coleoptera than to the Orthoptera, with which it agrees in scarcely any respect but its metamorphosis. The counterparts of this last Order indeed, instead of the Heteropterous, are to be sought for amongst the Homopterous Hemiptera, various species of which exhibit a most marked and multifarious analogy with numerous Orthoptera. Many of both Orders (Cicada, Locusta), as you have heard long since, are signalized by possessing the same powers of song, and produced by an analogous organ[1296]: a large proportion also of both are endued with wonderful saltatorious powers, and their posterior tibiæ are similarly armed; their legs in general likewise are longitudinally angular, and the head in both articulates with the trunk in the same manner[1297]. In both Orders too, the upper organs of flight are most commonly tegmina, but sometimes in both they are nearly membranous, like wings. In Centrotus and Acrydium, the one Homopterous and the other Orthopterous, the front is bilobed, the eyes are small; there are only two stemmata between the eyes; the prothorax is conspicuous, and behind is producted into a long scutelliform process, under which all the parts also are analogous; the abdomen articulates with the trunk in the same way, is similar in shape in both, and consists of short inosculating segments. Some Fulgoridæ and Truxalides agree also in their producted front. Other analogous characters might be named between these tribes, but these are sufficient to confirm M. Savigny's opinion. That the Neuroptera present analogies to the Lepidoptera, though they differ so widely from them in their metamorphosis and habits, is evident from the instance lately adduced of Ascalaphus italicus, which was described as a butterfly by Scopoli[1298]; and many of the Libellulina, by their wings, partly transparent and partly opaque, and by the shape of those organs and of their bodies, imitate the Heliconian butterflies: and this resemblance is much more striking than any that occurs between the perfect insects in the Neuroptera and Homopterous Hemiptera. With regard to the Hymenoptera and Diptera the analogy is undisputed, and must strike every beholder; and one would almost say it was a real affinity, were it not that the resemblance is not only general between Order and Order, but that almost every Hymenopterous tribe has its counterpart amongst the Diptera; the saw-flies[1299] for instance, the ichneumons, the various false-wasps[1300], the false-bees[1301], the bees, the humble-bees, the ants, &c., severally find there a representative that wears its livery and general aspect: a circumstance which evidently proves that it was part of the plan of the Creator to place them in contrast with each other. Were I to pursue this subject further, it might not be difficult to show that were the tribes of Mandibulata or of Haustellata also arranged in columns, analogies would be discoverable between their corresponding points: this seems to be Mr. MacLeay's opinion[1302]; and it is worth your pursuing the subject further, which cannot but prove very interesting.
But though the general analogy of these columns is that of Order to Order, yet individual species in each Order sometimes find their representatives in a different one from that with which they generally are contrasted;—thus some Diptera, as Culex, by the scales on the veins and other parts of their wings, are analogous to Lepidoptera rather than Hymenoptera[1303]; as is also the genus Psychoda by its form.
We come now to the consideration of a question not easy to be decided,—I mean, which Order of insects is to have the precedency, and which is the connecting link that unites them to Vertebrate animals.
Linné (and Mr. MacLeay seems in this to coincide with him) considered the Coleoptera as at the head of the Class of insects; De Geer thought the Lepidoptera entitled to that honour; Latreille and Cuvier begin with the Aptera: Marcel de Serres favours the Orthoptera[1304]; and others, on account of their admirable economy, have made the Hymenoptera the princes of the insect world[1305]. If the claim to priority was to be decided by the exquisiteness of instincts and the benefits conferred upon the human race, doubtless it would be in favour of the last-mentioned insects. If the power to do mischief carried it, and to lay waste the earth, the Orthoptera would be entitled as much as any to the bad pre-eminence. If beauty, and grace, and gaiety, and splendour of colours were the great requisite, and the law enjoined, Detur pulchriori,—the Lepidoptera would doubtless win the throne. But if perfection and solidity of structure, as they ought, are to regulate this point; we must, I think, with the illustrious Swede, assign the palm to the Coleoptera. If we consider these in all their parts, the organs for flight only excepted, they seem more perfectly formed and finished than the insects of any other order. But which of the Coleopterous tribes are entitled to the precedency? Linné placed the Lamellicorn beetles at the head of the order, beginning with the Dynastidæ, probably led by some characters which seem to connect these with the Branchiostegous fishes. In this he was followed by Fabricius. But Latreille and most modern Entomologists have begun with Cicindela and the other Predaceous beetles. I am not certain what are Mr. MacLeay's sentiments on this subject; but from what he says in the Annulosa Javanica[1306], it does not appear that he is a convert to the latter opinion. Bulk and strength seem the most striking characteristics of the former tribe, which represent the cattle or ruminants amongst Vertebrate animals.—Strength united with agility and a considerable portion of grace and symmetry evidently confers a degree of pre-eminence upon the latter, symbolizing the feline race, which seems to throw no small weight into their scale.
There are two Classes of Vertebrate animals with which insects may appear to claim kindred. The fishes, and the reptiles. Fishes in their fins exhibit no small resemblance to insects; the pectoral and ventral ones representing their arms and legs, and the dorsal ones their wings: Pegasus Draco in this last respect is not unlike a butterfly[1307]. In some genera (Ostracion, Pegasus, &c.), like insects the animal is covered with a hard shell or crust, formed by the union of its scales. The oral cirrhi of many fishes seem analogous to the palpi of insects; and in some a pair longer than the rest represent their antennæ[1308]. Another circumstance in which insects and fishes correspond, is the wonderful variety of forms, often in the greatest degree eccentric, that occurs in both Classes. Some of the cyclostomous fishes, as Ammocœtus, Gastrobranchus, are supposed to connect the fishes with the Annulosa, by means of the Annelida as an osculant Class[1309], which Mr. MacLeay regards as the passage to the Chilopoda[1310]: his Mandibulata he considers as passing into the Anoplura by means of some osculant Order as yet unknown[1311]. But I must confess I can see no good ground for this last transition:—the Anoplura appear much more nearly related to the Psocidæ, especially by the apterous Atropos pulsatoria[1312] than to any Coleopterous insect. But having stated these opinions, I shall leave you to draw your own conclusions, as the question is still perplexed with many difficulties. I am ready to admit that some Vertebrates approach near to the Annelida; but that it is through them alone that they are connected with insects, is not at present clear.
With regard to reptiles, they seem to be connected with insects by several characters. In the Chelonians, the skeleton merges in the external carapace or shell; the Ophidians change their skin like larvæ; the Batrachians undergo metamorphoses; some of the Saurians also have their changes: and the Draco volans has wings somewhat analogous to those of insects[1313]. Were I to be asked what Order of insects could connect with reptiles, I should point to the Orthoptera, especially Gryllus L., which by their noise and saltatorious powers not a little resemble frogs; and the larvæ of some strikingly imitate their form[1314]: and of others even that of a lizard[1315]. But these resemblances, after all, may only indicate analogies.