3<H< EXTERNAL ANATOMY OF INSECTS. 



greater sections — the Head, the Trunk, and the Limbs. 

 That of insects, likewise, is resolvable into three primary- 

 sections, but without including the limbs (which, as be- 

 ing appendages, and therefore secondary, had best be 

 considered under the section of which they form a part), 

 for the abdomen in insects, as well as the rest of the body, 

 being covered with a crust, and forming a distinct part, 

 may be properly regarded as a primary section. And in 

 fact these three parts may be received as primary under 

 another view — the head, as containing the principal or- 

 gans of sensation ; the trunk, as containing those of mo- 

 tion; and the abdomen, as containing those of generation* ■. 

 Under each of these primary sections, I shall consider its 

 respective organs, members, and parts. 



You are not to expect to find every part included in 

 the following Table in every insect; since it has been my 

 aim to introduce into it, the most remarkable of those 

 that are peculiar to particular tribes, genera, &c. With 

 respect to these, I shall generally refer you to the indivi- 

 duals in which they may be found. 



DEFINITIONS. 



Corpus (the Body). The whole crust of the insect; 

 consisting of the Exoderma or external covering, and 

 the Esoderma or internal cuticle that lines it b . It is 

 divided into three primary parts, or sections — Caput, 

 Truncus, Abdomen. 



a See above, p. 28 — . 



h The crust which covers the body of insects is lined internally 

 with a kind of iibrous cuticle. Query, Whether in any degree ana- 

 logous to the Periosteum of Vertebrate animals ? 



