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 Pulmonarice 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 ivliich either undergo no metamorphoses, or 
but imperfect ones; the three first orders. 
2. Apterous Insects which experience complete transformations ; 
the fourth. 
3. Insects having icings 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 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 Hippoboscce ; other cha- 
racters, however, and the nature of its metamorphoses, remove this 
genus from that of the Hippoboscse. 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, according to the 
ojjinion 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 m.outh, 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 
* Consul. Gener. sur I’ordrc des Crust., des Arach., et des Insectes, p. 46. 
