But it is not in the mere division of Insects into families and tribes that the philosophic naturalist meets with the greatest difficulty, but in assigning the situation which the whole class ought to occupy in the animal kingdom, both in regard to Insects themselves, and in their relations to other animals. Whether naturalists adopt as the basis of arrangement the development and perfection of the nervous system or that of the skeleton, with the organs of circulation and digestion, as compared with similar parts in other classes, they have usually been led to admit that while Insects are superior to many groups, which have been placed above them, in the former respects, they are inferior to them in the latter; and hence, although that portion of the animal body which is so all important to active existence, the nervous system, is employed without hesitation as the fundamental type and principle of arrangement, and in the vertebrated classes is scarcely ever departed from, it has become in the hands of many naturalists only of secondary importance in the invertebrated, and the greater perfection of the circulatory and digestive organs in the molluscous classes has induced them to place these, which in other respects are inferior in development, above the Articulated. We cannot, however, agree with those who consider the organs of nutrition alone of sufficient im portance to allow of this deviation from the fundamental principle of arrangement, neither can we admit with others that the nervous system of the higher Articulata is inferior to that of the higher Mollusks, the Cephalopoda, while we ourselves claim for the higher Articu lata the most decided superiority in the next essential character of arrangement—the deve lopment of the skeleton and organs of locomo tion.
Without entering further upon this difficult subject, we will simply state our conviction with Carus, Burmeister, and others, that the articulated ought to stand at the head of the invertebrated classes, seeing that they contain among them some of the most completely organized of invertebrated animals. We shall reserve for the present our explanation of the steps by which we propose to pass from the lowest vertebrated forms to these, in our esti mation, the highest of the invertebmted, and proceed to consider the arrangement of Insects, as a class, as proposed by different naturalists, before we enter upon an examination of the peculiarities of these animals.
The principles upon which naturalists have attempted to arrange this interesting class have been almost as various as the systems proposed. Aristotle among the ancients arranged Insects with reference to the presence or absence of the organs of flight; and although he was far more successful than many of his successors in separating from Insects the Crustacea, as a dis tinct class, his arrangement of Insects is not entirely natural, since it separates some of the most nearly connected families. Among the moderns, Aldrovandus, in the beginning of the seventeenth century, divided them into land and water Insects, and subdivided these groups into families according to the structure of their wings and legs. Swammerdam many years afterwards first proposed to arrange Insects with reference to their metamorphoses ; first, those which undergo only a partial or incom plete metamorphosis, and, secondly, those which undergo a true or complete one. The latter he again divided into those which undergo a slight change of form, but are active during the pupa state ; secondly, those which have distinct limbs but are inactive in that condition; and, lastly, those which have no external development of wings or legs, but remain as inactive ovate pupa:. This was the first step towards arranging
Insects upon a truly natural system ; since, as Messrs. Kirby and Spence have justly ob served,• although the employment of the meta morphoses taken alone leads to an artificial arrangement, it is of the greatest use in con nexion with characters taken from the perfect Insect, in forming a natural system. Our illustrious countryman Ray, in the beginning of the eighteenth century, followed the example of Swammerdam in arranging Insects primarily according to their metamorphoses; and Lister, in 1710, followed with a modification of Ray's classification, after which nothing further was proposed until Linnteus published the first edi tion of his Systema Naturm in 1735. His arrange ment was based upon the form and structure of the wings. By these he divided Insects into three groups. First, those with four wings, in which he included in three divisions those Insects which now constitute his orders Coleoptera, Hemiptera, Lepidoptera, Neuroptera, and Hy menoptera. In the second group he placed Insects with two wings, his single order Dip tem ; and in the third, Insects without wings, his order Aptera. In this arrangement, founded partly upon that of Aristotle, Linnaus was particularly successful in establishing some very natural series, although in including the Crus tacea among his Aptera, like Swammerdam and Ray, he receded a little from a natural system. After Linnaus, Degeer and Geoffroy each proposed a new arrangement, but it was not until an entirely new set of organs had been selected by Fabricius that Insects began to be arranged upon truly natural principles. The parts from which Fabricius drew his cha racters were those of the mouth, by which he divided Insects primarily into two sections, the Mandibulated, or those furnished with jaws for comminuting their food, and the Haustellated, or those which take their aliment by means of a flexible elongated proboscis, without distinct manducatory organs. But the difficulty of forming a strictly natural system still existed, so long as the characters employed were derived only from particular sets of organs, and not from a consideration of the whole. Cuvier, by founding his arrangement upon an examination of all the external organs, and thereby establish ing natural families, advanced very far towards the object desired, and was followed by La treille, Lamarck, Dumeril, Leach, Kirby and Spence, and MacLeay, who continued to im prove the arrangement of the class. These have been followed by Messrs. Stephens and Curtis, and very recently by Mr. Westwood, the inde fatigable Secretary of the Entomological Society, each of whom has proposed a different arrange ment. But none of the systems hitherto pro posed are entirely satisfactory, so great indeed is the difficulty of discovering the connecting links of families, which, distributed over the whole globe, are believed to include from 100,000 to 150,000 distinct species ; and this difficulty will probably continue until the in ternal as well as the external organization is better known in a greater number of insects than it is at present, and applied to their arrangement, as has lately been done by Bur meister. In the succeeding pages we shall adopt the arrangement of Mr. Stephens, giving a synoptical view of the families, with the addition of some of the recently established foreign ones, and shall also add particular descriptions of some of the most remarkable, referring our readers for more minute descrip tions of them to Mr. Stephens's admirable into two tribes, Adephaga and Rhypophaga, and these are divided into four sub-tribes.