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Show 232 lNS~"CTA. unde1·taken at my request, by the late Laehat. His fl'iend, M. Victor Audouin, has prosecuted his researches and pre· sen ted to the Academic des Sciences an excellent memoir on the subject. All that is yet known of it ~1ow.eve~ is from the general sketch given by the Baron Cuv1er m Ius report(l) ( 1) The exposition of the parts of the thorax, and a fixed nomenclature created for them, says the Baron in his repot·t, sh~~l~ na~urally be place~ at the head of the work The trunk of Insects is always diVISible mto three :mnul1, each of which bears a pait· of legs, called by M. Audouin, from their position, the protltwax, the mesotltOrax, and the metatltOrax. Besides these legs, the mesothorax bears the first pair of wings, and the meta thorax the second. Each of ~hese three segments is composed of four parts: one inferior, two late.ral ~for~rung the pectus), and a fourth superior, which constitutes the back; the mfet·wr ts called the sternum; the lateral portion, or the flank, is divided into three prin~ipal parts, one which is attached to the sternum, called episternum, another behmd the first, and to which the coxa is articulated, the epimera (epimere). A little movable piece, hitherto unknown, which serves to unite the cpimera and the coxa, is named lroclwntinu!, (trochantin) by way of distinguishing it f1·om tt·o~ha.nter. The third pie~e of the flank, which in the mesothorax and metathorax IS s1tuated before the ep1sternum and under the wing, is called the !typotltera. Sometimes there is also a small cor. neous piece round the stigma, styled the peritrema. The superior portion of each segment, which the author calls tergum, is divided into four pieces, named, from their position in each ring,prreswturn, scutum, undpostscutellum. The firstisfre· qucntly, and the foUl'th almost always, concealed in the interior. Naturalists.hav.e seldom distinguished any other part of the mcsothorax but the scutellum, wh1ch 11 frequently remarkable for its large size uncl its configuration, although an nnal.o~ous piece is found in the three segments. Thus the trunk of Insects may be diVJd~ into thirty-th1·ee principal parts, and, if we count the hypothcru, the 1mmber Will amount to forty-three, more or less visible in the interior. From these piece~ besidC's, arise vat·ious internal productions, which, on account of their uses and im· partance, require to be named: thus, f1·om the posterior portion of the sternum of each segment, a vertical apophysis arise internally, sometimes shaped like a Y, called by M. Audouin the entotlwraz. It furnishes insertions to muscles and protects the medullary cord; an a.nalogous one is seen in the head and sometimes in the first annuli of the abdomen. Other internal prominences result from the prolongation of the external neighbouring pieces that are solde1·ed together. M. Au· douin names them apoderna (apodcmes ). Some of them give insertion to muscle~ others to the wings:-finally. there are other small movable pieces either internally and between the muscles, or at the base of the wings, which our author styles the ( epidemes) epidema. We have stated that the principal pieces, or vestiges of them, are always to be found, but they a.re ft·equently fur from being separable. In par· ticular genera, or in certain orders, many are only to be distinguished by traces~( sutures. 1\f. Audouin-Dict. Cbss. d'llist. Nat., art. lnsectes-hns since substi· tuted the name of paraptera for that of hypoptcra. That of entothorax will also be changed, in some situations, into entocepltala, relative to the head-and into enlo· gaster, as respects the abdomen. lie remarks that the hc:ul of Insects is composed of several segments. We have also observed, that the rostrum of the Cicndre, repre· INSECTA. 233 and by the extract published by the author in the article INsECTES of the Diet. Class. d'Histoire N aturelle. Before we can adopt his nomenclature, and apply it generally, we must wait until his work and the figures which accompany it are published; for all practical purposes, however, the denominations already introduced may suffice. A second production relative to the same subject, which both justice and friendship here compel me to notice, is that of M. Chabrier on the flight of Insects. It forms part of the Mem. du Mus. d'Hist. Nat., but is sold separately. The figures are executed on a great scale, as are also those of a Memoir of J urine, Sen. on the wings of the Hymenoptera, a work, like the preceding one, which is the result of infinite patience. As Insects inhabit all kinds of dwellings, they are provided with all sorts of locomotive organs, wings and feet, which in several, act as fins. · The wings are membranous, dry, elastic organs, usuaJiy diaphanous, and attached to the sides of the back of the thorax: the first, when there are four, or when they are unique, on those of its second segment, and the second on those of the following or of the metathorax. They are composed of two membranes laid one on the other, and are traversed in various ilirections by more or less numerous nervures, which are so many tracheal tubes, now forming a network, and then simple veins. A celebrated naturalist, J urine, Sen., has taken advantage of the disposition and decussation of these nervures(l) in a systematic point of view. The Libellulre, Apes, Vespre, Papiliones, &c., have four wings; but those of the latter are senting the lower lip, is not attached to the head, but to the membrane which unites it with the thorax, and thus also we find that the two meclulhry cords form two contiguous ganglions under the mouth. In accordance with these views, we consider the first segment of the body of the Scolopendrre, that which bears the tw~hooks, ns an analogous. division of the head. It seems that Knoch had distinguished the epimera by the names of acapulre and parapleur<e; the post-pectus by that of acetabul"m, while the mediopectus was his peristretltium. The first joint of the four posterior coxa:, in most of the Coleoptera, forms a transverse plate endo~ ed in the flanl!;s, and is the piece, as far as I can judge, that he calls the mrerium. ( ) See general observations on the Hymenoptera. Vor. III.-2 E |