476 Div. 3. ARTICULATED ANIMALS. 



the teguments themselves, each of wliich bears a breathing pore, so that the sides of 

 the abdomen exhibit a longitudinal series of small pieces, or each segment is, as it were, 

 divided into four. Other pieces, also corneous, occupy the lower sides of the meso- 

 thorax and metathorax, immediately beneath the insertion of the elytra and wings, 

 which are supported by another piece, placed longitudinally. The relations of these 

 parts, the size and form of the first joint of the coxse, or haunches, the manner in which 

 they articulate with the semi-ring to which they are attached, and the extent and 

 direction of this variable semi-ring, furnish the thorax, considered in this respect, with 

 a combination of characters which is Very serviceable in a systematic point of view. 

 Some naturalists, especially Knoch, had already made use of them, but without any 

 determined principle, and with arbitrary names. It was, however, necessary to study 

 the composition of the thorax carefully, in all the classes of insects — a task commenced 

 by the late Lachat, and followed up by M. Victor Audouin, who presented a memoir 

 on this subject to the Academie des Sciences. It is, however, only known to us by 

 the general sketch of it given by Cuvier in his Report*, and by the extract published 

 by its author in the article Insect in the Dictionnaire Classique d'Hist. Nat. To 

 adopt this nomenclature, and give it a general application, we must wait for this memoir 

 and its illustrative figures ; but in practice, the denominations already introduced will 

 suffice. Another memoir, upon the same subject, by M. Chabrier, with admirable 

 figures, and one by the elder Jurine upon the wings of the Hymenoptera, must also be 

 mentioned. 



As insects inhabit all kinds of situations, they have all the kinds of locomotive organs : 

 namely, wings and legs, which last, in many species, are used as oars. The wings are 

 membranous, dry, elastic, generally transparent, pieces attached to the sides of the back 

 of the thorax ; the anterior pair, when there are four, or when they are the only pair, 

 being upon the mesothorax, and the posterior pair upon the following segment, or 

 metathorax. They are composed of two membranes applied upon each other, and tra- 

 versed, in various directions, by more or less numerous nervures, which are so many 

 trachean tubes, forming sometimes a network, and sometimes simply veined. The elder 

 Jurine has advantageously employed the disposition and crossing of these nervures in 

 systematic arrangement. The Dragon-flies, Bees, Wasps, Butterflies, &c., have four 

 wings ; but those of Butterflies are covered with small scales, which at first sight re- 

 semble dust, and which give these insects the colours with which they are ornamented. 

 They easily come off on being touched by the finger, and the portion of the wing from 

 which they have been taken is transparent. With the microscope, these scales appear 

 of varied figures, and are imj)lanted upon the wing by means of a footstalk, and 

 arranged regularly in rows like the tiles of a roof. In front of the fore-wings of these 

 insects are a pair of pterygoda (a kind of ejjaulettes), which extend backwards along 

 a part of the back, upon which they are applied. In certain insects, the wings remain 



• [A loiijf note is here K'vcn in tlie second edition, cniitaining tlic 

 delniU of M. Audouin'tt rt'sc«rulu*s. 1 chii, however, only introduce 

 the followini; sligiit abridgment : — The trunk, or thorax, is nlwavs 

 typically divi.siblc, on the outsiilc, into three sci,'ments, each hcarinff 

 a pair of ftet, — namely, the proth<(rax, nic»othorax (beari[i)f the fore 

 winj;s), and metathorax (hearing; the hind winifs) Kaeli sei^ment is 

 eomposed of four jinrts : one inierior, two lateral (tliese three fornnnt,' 

 the breast), and otie dorsal, forming the hack. The inferior part is 

 the Hternutn ; the lateral pieces, or Aanks, are each divisible into three 

 principal pieces; one (the episterinun) attaelied to the sternum, 

 another (the epimeron), articulalinjf with the coxa. Another small 

 piece (the Irochanttne) assists in th'j union of the epimeron and coxa, 



whilst the third piece of the rt'ink is placed, in the meso- and meta- 

 thorax, beneath the wini;, and is called the hypoptcra, since cliant;ed 

 by Audouin to paraptera. The dorsal part, or tergunl, is divided into 

 four pieces, named, from their position in each segment, the prre- 

 sculum. scutum, scutellum, and postscutcllum : the first of which is 

 ollen, and the last nearly always, internal. Thus the thorax is divi- 

 sible into thirty-three princip:il pieces, or forty-three, indudinij the 

 hypoptcra. The epimera had been previously called scapulie, and 

 parapleurtc, by Knoch. "riic posterior coxa of the Coleopteia, formintf 

 a transverse plate, is his nuerium. Mr M'l.cay has subsequently pub- 

 lished ati elaborate niennnr upon the structure of the thorax in the 

 ZiJulogii:al Ji/urtiat,^ 



