In this arrangement of the tribes, as he calls them, of Mandibulata, Mr. MacLeay sets out from the Coleoptera, which he distributes, according to the supposed typical forms of their larvæ, into five minor groups, sufficiently noticed on a former occasion[1447]. From this tribe or Order he proposes to pass by Atractocerus to the osculant Order Strepsiptera, and from thence by Myrmecodes and the Ants to the Hymenoptera. From hence he next proceeds to his Trichoptera; in which, as we have seen[1447], he places not only Phryganea L., but also Tenthredo L. and Perla Geoffr., making his transit by Sirex L.; forming an osculant Order which he denominates Bomboptera. From this his way to the Neuroptera is by the Perlides, with Sialis as an osculant Order under the name of Megaloptera: he enters by Chauliodes, and leaves it by Panorpa or Raphidia by means of Boreus, forming also an osculant Order (Raphioptera) for the Orthoptera; which he enters by Phasma, Mantis, &c., and leaves by Gryllus, entering the Coleoptera again by the osculant Order Dermaptera formed of Forficula L.: and thus returning to the point from which he set out[1448]. He has not, however, made this return of the series into itself so clear in each order, excepting in the Orthoptera, as he has done in the whole Class or Sub-class. Thus in the Coleoptera there appears no particular affinity between the Predaceous and Vesicant beetles, his first and fifth forms[1449], or his Chilopodimorphous Coleoptera, and his Thysanurimorphous.
To enter fully into his doctrine of Analogies would lead us into a very wide field, and occupy a larger space than I can afford; I must therefore refer you to his work for more particular and detailed information on that subject. With regard to the analogy between opposite points of contiguous circles, you may get a very good idea of it from his diagram of Saprophagous and Thalerophagous Petalocerous beetles, which I here subjoin.
It is a very singular circumstance that in these two circles we have two sets of insects,—one impure in its habits and feeding upon putrescent food, and the other clean and nourished by food that has suffered no decay,—set in contrast with each other, and that in each of the opposite groups, the one has its counterpart in some respect in the other. In none is this more striking than the Scarabæidæ and Cetoniadæ, both remarkable for having soft membranous mandibles unfit for mastication, and both living upon juices, the one in a putrescent and the other in an undecayed state[1450]. Our learned author in subsequent works has stated every circle to be resolvable into two superior groups, which he denominates normal or typical, and three inferior ones, which he calls aberrant or annectent[1451].
Before I conclude this account of the various general systems that have distinguished the different entomological eras, i must say a few words on those partial ones which have been founded on the neuration of the wings of insects. Frisch, who died in 1743, attempted something in this way[1452]: Harris, in his Exposition of English Insects published in 1782, had arranged his Hymenoptera and Diptera according to characters derived from this same circumstance[1453]: Mr. Jones in the Linnean Transactions had made good use of it in dividing the Diurnal Lepidoptera into groups[1454]: and in the Monographia Apum Angliæ, the characters exhibited by the various groups into which Linné's genus Apis was resolvable, as to the neuration of their wings, were described[1455]. But M. Jurine was the first Entomologist who made that circumstance the keystone of a system; which indeed he restricted to Hymenopterous and Dipterous insects, but which might be extended much further. As this system has been before sufficiently enlarged upon[1456], I need here only mention it.
To particularize the various entomological works in every department of the science, that have appeared since the commencement of the era of Fabricius, would require a volume. Such was its progress and spread, that in every corner of Europe the pens and pencils of able and eminent men, whose works have almost all been quoted in the course of our correspondence, have been employed to illustrate it[1457]. I may observe, however, that the Internal Anatomy of Insects, a branch of Entomology which on account of its difficulty, from the extreme nicety required in dissecting them, had before been cultivated by scarcely more than a single student in an age, has now attracted numerous votaries. In Germany—Carus, Gaede, Herold, Posselt, Ramdohr, Rifferschweils, Sprengel, and others, have distinguished themselves in this arena: and in France, besides the illustrious Baron Cuvier (himself a host), Marcel de Serres, Leon Dufour, and very recently, by his elaborate essays On the Flight of Insects and its wonderful apparatus, one of the most acute of anatomical physiologists, M. Chabrier,—have all contributed greatly to the elucidation of this interesting part of the science. In our own country very little has hitherto been effected in this line; but a learned Oxford Professor (Kidd) has presented to the Royal Society an account of the anatomy of the Mole-cricket, which entitles him to an eminent station amongst the above worthies.
I may likewise further observe, that the pictorial department of Entomology was, during the period I am speaking of, carried to its greatest perfection. Painters of insects formerly were satisfied with giving a representation generally correct, without attempting a faithful delineation of all the minor parts, particularly as to number;—for instance, the joints of the antennæ and tarsi, the areolets of the wings, &c.: but now no one gives satisfaction as an entomological artist unless he is accurate in these respects.