TO THE ARTICULATED ANIMALS. 403 



the following considerations : — 1st, Wingless insects, with incomplete metamorphoses, 

 or which do not undergo any change, comprising the first three orders ; Sndly, Wingless 

 insects, undergoing complete metamorphoses, comprising the fourth order ; and, 3rdly, 

 Insects with wings, which they acquire by metamorphosis, either of an incomplete or 

 perfect kind, containing the last eight orders. The first of these primary groups cor- 

 responds with Lamarck's Arachnides antennistes ; the second, consisting of the single 

 genus Pulex [or the flea], appears, in some respects, to be related by means of the genus 

 Hippobosca [or forest flies], with the order Diptera, although, in other respects, and in 

 its metamorphoses, it is removed from the genus last named. It is, moreover, often 

 difficult to distinguish these natural enchainments ; and often, even when discovered, 

 we are compelled to sacrifice these relations to the precision and facility of our [arti- 

 ficial] methods. 



To the before known orders of insects I have added that of Strepsiptera (Kirbt/), 

 but under the name of Rhipiptera, — the former appearing [but erroneously] to me to 

 be founded upon an incorrect supposition. Perhaps, indeed, this order might be sup- 

 pressed, and united with the Diptera, as Lamarck had suggested. 



For the reasons assigned in my Considerations Ginerales, 8fC., p. 46, and which I 

 might support by other proofs, I have attached more weight to the characters derived 

 from the organs of locomotion, and the general construction of the body, than to the 

 modifications of the mouth-organs, at least when their structure is referable to the same 

 type. Hence I do not divide the class first into gnawing and sucking insects, but into 

 those with wings, or wing-cases, &c., nearly similar to the series of the Linnaean orders, 

 using, in a secondary sense, the characters derived from the mouth-organs, which had 

 been placed in the foremost rank by Fabricius, Cuvier, Lamarck, ClairviHe, and 

 Dumeril, whose arrangements consequently differ from mine. 



I have followed Cuvier in reducing the number of families proposed in my former 

 works, and in converting into subgenera the groups separated from the Linnaean genera, 

 although their characters appear to be sufficiently distinct. Such was also the plan of 

 Gmelin, which is simple and advantageous, by bringing the subject more within the 

 capacity of the student. 



All my groups are founded upon the comparative investigation of all the parts of the 

 animals which I desire to make known, and upon the observation of their habits. It is 

 from being too exclusive in their considerations, that the majority of naturalists entirely 

 lose sight of the natural system {I'ordre naturel). 



To the facts recorded by Reaumur, Roesel, De Geer, Bonnet, the Hubers, &c., upon 

 the instincts of insects, I have added many collected by myself; while the works of 

 Cuvier, L. Dufour, M. Serres, Strauss, Audouin, and Millie Edwards, have furnished 

 me with anatomical observations. As I have been able to describe but a very small 

 number of insects, I have selected the commonest and most interesting species. 



[Such is a condensed abstract of the introductory observations of Latreille, from 

 which it will be seen that the period of ten years, which had elapsed between the pub- 

 lication of the first and second editions of this work, had rendered it necessary to double 

 the space assigned to the Linnaean Insecta, which, in the second edition, occupied up- 

 Avards of 1100 pages. The latter was published in 1829 ; and If we contrast the ten 

 years which have elapsed since that period with the ten preceding, we shall be com- 



