Entomology for beginners; for the use of young folks, fruitgrowers, farmers, and gardeners; . es of Insects.—It is difficult to explain many ofthe actions of insects, from the fact that it is hard for us toappreciate their instincts and general intelligence. Thatthey have sufficient intellectual powers to enable them tomaintain their existence may be regarded as an axiom. Butinsects differ much in intelligence, and also in the degree ofperfection of the organs of sense. The intelligence of in- * See Miall and Dennys The Cockroach, p. 163. 22 ENTOMOLOGY. sects depends, of course, largely on the
Entomology for beginners; for the use of young folks, fruitgrowers, farmers, and gardeners; . es of Insects.—It is difficult to explain many ofthe actions of insects, from the fact that it is hard for us toappreciate their instincts and general intelligence. Thatthey have sufficient intellectual powers to enable them tomaintain their existence may be regarded as an axiom. Butinsects differ much in intelligence, and also in the degree ofperfection of the organs of sense. The intelligence of in- * See Miall and Dennys The Cockroach, p. 163. 22 ENTOMOLOGY. sects depends, of course, largely on the development of theorgans of special sense, especially those of sight and smell. There are in nearly all insects two kinds of eyes, the simpleand the compound. Of the simple eyes there are usuallythree, arranged, as in locusts, bees, etc., in a triangle on thetop of the head. There is a single pair of compound simple eye, or ocellus, consists of a single smooth, shin-ing, convex area, called the cornea or facet, while in thecompound eyes there are many facets, which can be seen. FIG. 18.— Longitudinal section of the faceted eye of a moth. /, the rod-likeending of the optic nerve-flbivs; k. crystalline lens; sn, optic nerve; tr,trachea lost in fine fibrillfe ; ». c/i, retina.—After Leydig, from Graber. with a hand-lens. The compound eyes, which are usuallyround and very prominent, differ much in size and thenumber of facets, the latter varying from fifty, as in the ant,to several, even twenty, thousand, as in certain beetles. The structure even of the simple eye is too complicatedfor description here, but the essential parts are° the cornea, THE SENSES OF INSECTS. 23
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Keywords: ., bookcentury1800, bookdecade1880, bookpublishe, booksubjectinsects
