154 PHYSIOLOGY OF INSECTS. 



lateral spaces, CE OS, the eyes : the plate below the fore- 

 head, £6, represents the nose, and is so called by Kirby, 

 the lower extremity of it being termed by Mr. Kirby the 

 rhinarium or nostril-piece, probably from its frequently 

 covering the base of the antennae, y y, which in situation 

 are precisely similar to the nostrils of vertebrate animals : 

 below this plate is the upper lip, a, and immediately under 

 this is the aperture of the mouth, the space on each side 

 of the nose is analogous to a cheek. Mr. Kirby's no- 

 menclature of the parts of insects is drawn from these 

 analogies with similar parts in suj)erior animals, but so 

 many of his presumed analogies appear fanciful or far- 

 fetched, that his nomenclature has been universally re- 

 jected. 



It is supposed that the head of insects, like the following 

 segments, is composed of four smaller portions or sections ; 

 in this instance, however, they are not merely distinguished 

 by sutural lines, but perfectly separated and freely articu- 

 lated : these are the skull or cranium, the upper and low- 

 er lips — lahriim and labium, the feeler-jaws or maxill<B, 

 and the jaws or mandibles,- mancUhulce : the lips, jaws, 

 and feeler-jaws, constitute the mouth of an insect. If we 

 were to assign to these parts names in accordance with 

 those of the^ro- meso- and metathorax, we should call the 

 jaws the pr(BScutiim, the feeler-jaws the scutum, the lips 

 the scutellum, and the skull the postscutelliim. Some 

 writers have suggested that the divisions of the head are 

 of equal importance with the following segments, and al- 

 lowing three or sometimes four segments for the head, have 

 increased the total number to fifteen or sixteen. Each 

 section of the head has a tendency to produce two feelers : 

 on the last — the mandibles — they are obsolete ; on the skull, 

 lips, and feeler-jaws, they are very distinct: in the lobster 

 and other animals resembling it, which are closely related 



