372 STRUCTURE OF INSECTS. 



sense of seeing, and that which is usually called touch, 

 the senses of insects have not been referred to any 

 particular organs. 



The structure of insects is altogether a very curious 

 matter, at least, a matter different from those animal 

 structures with which we are the most familiar, and 

 which we are, in consequence, too apt to take as our 

 standards. They are all annulose animals, that is, have 

 their bodies divided across into a greater or smaller 

 number of rings or segments. They are without a 

 spine, or any thing like an internal skeleton, and thus 

 the insertions of all the muscles, by which their parts 

 are moved, are on the external covering, which is to 

 them at once both skin and skeleton. 



That skin, though it do not contain, even in those 

 that have it the hardest, carbonate of lime, like the 

 crusts of crabs and lobsters, and the shells of oysters 

 and snails, is yet more like a horny substance than 

 the skin'of those that we call the more perfect animals. 

 The substance in the skin of the more perfect animals, 

 which the covering of insects the most nearly resembles, 

 is the epidermis, or scarf-skin ; and there is no appear- 

 ance of vessels in its structure, or of a mucous net or 

 true skin. In its composition, it is a good deal like horn, 

 though it is not fibrous, like that substance. It also 

 varies more in hardness, being in some as hard as horn, 

 and in others as flexible as leather ; in some, too, it is 

 elastic, and may be bent considerably and resume its 

 form, while in others it is exceedingly brittle. The 

 pincers, stings, claws, mandibles, and all the grasping, 

 cutting, and piercing organs of insects, are formed of 

 the same substance, though thickened and hardened 



