10 CLASS INSECTA. 



form of a beak (rostrum), or membranous or fleshy, unarti- 

 culated, and terminated by two lips (the proboscis). The 

 labrum is triangular, vaulted, and covers the base of the 

 sucker. In the second kind of organization, the labrum and 

 mandibles are almost obliterated and extremely small. The 

 lip is no longer a free body, and is distinguished only by 

 the presence of two palpi, of which it is the support. The 

 jaws have acquired an extraordinary length, and transformed 

 into two tubular threads, which, uniting at their edges, form 

 a sort of proboscis, which rolls into a spiral form, and is 

 usually named tovgiie ; but which, to avoid all equivoque, 

 it would be preferable to call spiral proboscis or tongue 

 (spirignatha)* Its interior exhibits three canals, the middle 

 one of which is the conduit of the nutritive juices. At the 

 basis of each of these threads is a palpus, usually very small, 

 and but little apparent. 



The myriapodes, or millipedes, are the only insects whose 

 mouth shews a different type of organization, which I shall 

 describe when I come to treat of them. 



The trunkf of insects, or that intermediate part of their 

 body to which the feet are attached, is generally designated 

 by the Latin name of thorax, which has been rendered into 



* Kirby calls it antlia. — Ed. 



-j- This denomination is here synonymous with that of thorax. I am of 

 opinion, however, that to avoid all embarrassment, we should ajiply the 

 first term only to the apterous insects of Linnaeus, which have more than 

 six feet, and in which these organs are attached to segments proper to 

 them ; that is, in which the head is distinct from the trunk. With regard 

 to the Crustacea in which these parts of the body are confounded, the 

 thorax should take the name of thoracida, and that of cephalothorax 

 in the arachnida ; animals which exhibit the same character, but in which 

 the trunk or thorax is more simple, and provided with less numerous 

 appendages. The entomostracea even approximate, in this respect, to 

 these latter animals ; but as they belong to another class, the term thora- 

 cida should be preserved for them — that of thorax should be exclusively 

 reserved for the hexapod insects. 



