VI PREFACE. 



I divide the Insects of Linnaeus, with him, into three 

 classes : the Crustacea, Arachnides 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 ex- 

 ceptions^). 



The situation and form of the branchiae, the manner in 

 which the head is united to the thorax, and the organs of man- 

 ducation, have furnished me the means of establishing seven 

 orders in the class of the Crustacea, all of which appear to 

 me to be natural. I terminate it, with M. de Lamarck, by 

 the Branchiopoda, which are a sort of Crustacea Jlrachnides. 



In the following class, that of the Arachnides, I only in- 

 clude the species which in the system of Lamarck, compose 

 the order of his Arachnides paipistes, or those which have 

 no antennae. 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 

 air through concentrated stigmata, sometimes possessing func- 

 tions analogous to those of lungs, and consisting at others of 

 radiated tracheae, or such as ramify from their base; the an- 

 tennae are wanting, and they are usually furnished with eight 

 feet. I divide this class into two orders: the Pulmonarise 

 and the Trachearise. 



Two parallel tracheae, 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, 

 as may be seen by a reference to the historical sketches which precede the expo- 

 sition of those families. I have even been employed on a work respecting the 

 metamorphosis of Insects in general, which has not yet been published (see article 

 " Insectcs" Nouv. Diet. d'Hist. Nat. Ed. 2d), but which I have long been matur- 

 ing, and which I have communicated to my friends: I have made use of it in the 

 course of my general remarks. 



