VI PREFACE. 



Their organs of respiration are always internal, receiving air 

 through concentrated stigmata, sometimes possessing functions ana- 

 logous to those of lungs, and consisting at others of radiated tracheae, 

 or such as ramify from their base ; the antennae are wanting, and 

 they are usually furnished with eight feet. I divide this class into 

 two orders : the Pulmonariee and the Trachearice. 



Two parallel tracheae, extending longitudinally through the body, 

 furnished at intervals with centres of branches corresponding to the 

 stigmata, and two antennae, characterize the class of Insects. Its 

 primary divisions are founded on the three following considerations : 



1. Apterous Insects which either undergo no metamorphoses, or 

 but imperfect ones; the three first orders. 



2. Apterous Insects which experience complete transformations; 

 the fourth. 



3. Insects having wings which they acquire by metamorphoses, 

 either complete or incomplete; the last eight. 



I begin with the Arachnides antennistes of M. de Lamarck, which 

 are comprised in this first division, and which form out 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 Hippoboscce; other cha- 

 racters, however, and the nature of its metamorphoses, remove this 

 genus from that of the Hippobosca?. 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 

 R/u'piptera, as the former appears to me to be founded on a false 

 idea. Perhaps we should even suppress this order, according to the 

 opinion of Lamarck, and unite it with that of the Diptera. 



For reasons elsewhere developed*, and which I could easily 

 strengthen by additional proof, I attach more consequence to cha- 

 racters 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 1 do not commence by dividing 

 these animals into Grinders and Suckers, but into those which have 

 wings and wing-cases, and such as have four or two wings of the 



* Consid. G<?nr. sur 1'ordre des Crust., des Arach., et des Insectes, p. 46. 



