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Show vi I divide the Insects of Linnreus, with him, into three classes: the Crustacea, .!lrachnides and Insecta; but in the essential characters which I assign to them, I abstract all the changes experienced by these animals, prior to their adult state. This consideration, although natural, and previously employed by De Geer in his arrangement of the Aptera, is not classical, inasmuch as it supposes the observation of the animal in its different ages ; it is, besides, liable to many exceptions( l ). The situation and form of the branchire, the manner in which the head is united to the thorax, and the organs of manducation, have furnished me the means of establishing seven orders in the class of the Crustacea, all of which a1)pear to me to be natural. I terminate it, with M. de Lamarck, by the BranchiojJoda, which are a sort of Crustacea .ll.raclmides. In the following class, that of the Arachnides, I only include the species which in the system of Lamarck, compose the order of his .fl.rachnides palpistes, or those which have no antennre. Beyond this, the organization of these animals, external as well as internal, furnishes us with a simple and rigorous rule that is susceptible of a general application. . Their organs of respiration are always internal, receiving a~r through concentrated stigmata, sometimes possessing functions analogous to those of lungs, and consisting at others of radiated trachere, or such as ramify from their base; the antenure are wanting, and they are usually furnished with eight feet. I divide this class into two orders: the Pulrnonarim and the Trachearim. Two parallel trachere, extending longitudinally through the body, furnished at intervals with centres of branches corres- (1) These considerations, however, have not been overlooked, and I have used them advantageously in grouping families, and arranging them in a natural order, a.s .may be seen by a reference to the historical sketches which precede the expo· !ttlon of those families. I have even been employed on a work respecting the metam01·phosis of Insects in general, which has not yet been published (see article ." Insectes," ~ouv. Diet. d'Ilist. Nat. Ed. 2d), but which I have long been mattll'· mg, and wluch I have communicated to my friends: 1 have made use of it in the course of my general remarks. " PREFACE. vii ponding to the stigmata, and two antennre, characterize the class of Insects. Its primary divisions are founded on the three following considerations : 1 . .llpte1·ous Insects which either undergo no metamorphoses, or but imperfect ones; the three first orders. 2. .ll.pterous Insects w!tic!t experience complete transfor· mations; the fourth. 3. Insects having wings u·hich they acquire by metamorphoses, either complete m· incomplete; the last eight. I begin with the .fl.rachnides antennistes ofM. de Lamarck, which are comprised in this first division, and which form our three first orders. The second is composed of the fourth order, and contains but a single genus, that of Pulex: it would appear, in some respects, to be allied to the Diptera by means of the Hippoboscm; other characters however, and the nature of its metamorphoses, remove this genus from that of the Hippoboscre. It is very difficult in some cases to distinguish these natural filiations, and when we are fortunate enough to discover them, we are frequently compelled to sacrifice them to the perspicuity and facility of the system. To the known order of winged Insects, I have added that of the Stresiptera of Kirby, but under a new denomination, viz. that of Rhipiptera, as the former appears to me to be founded on a false idea. Perhaps we should even suppress this order, ac.cording to the opinion of Lamarck, and unite it with that of the Diptera. For reasons elsewhere developed( 1 ), and which I could easily strengthen by additional proof, I attach more consequence to characters drawn from the aerial locomotive organs of Insects, and to the general composition of their body, than to the modifications of the parts of the mouth, at least when their structure is essentially referable to the same type. Thus I do not commence by dividing these animals into Grinders and Suclwrs, but into those which have wings and wing-cases, and such as have four or two wings of the same consistence. The form and uses of the organs of manducation are viewed (1) Consid. Gencr. sur l'ordre des Crust., des Arach., et des Insectes, P· 46. |
