20 FUNCTIONS OF INSECTS. 



INSECTS. 



The insect division of the animal world received its name from the individuals of 

 which it is composed having a separation in the middle of their bodies, by which 

 they are cut, as it were, into two parts. These parts are in general connected by a 

 lender ligament or hollow thread. 



Insects breathe through pores arranged along their sides ;* and have a scaly or 

 bony skin, and many feet. Most of them are furnished with wings. They are desti- 

 tute of brain, nostrils, and eyelids. Not only the place of the liver, but of all the 

 secretory glands, is, in them, supplied by long vessels that float in the abdomen. 

 The mouth is in general situated under the head ; and is furnished with transverse 

 jaws, with lips, a kind of teeth, a tongue, and palate : it has also, in most instances, 

 four or six palpi, or feelers. Insects have also movable antennae, which generally 

 proceed from the front part of the head, and are endowed with a very nice sense of 

 feeling. 



In a minute examination of this class by Professor Cuvier, neither a heart nor ar- 

 teries have been detected ; and this gentleman says that the whole organization of 

 insects is such as we might have expected to find, if we had previously known that 

 they were destitute of such organs. Their nutrition, therefore, seems to be carried 

 on by absorption, as is the case with the polypes, and other zoophytes, t 



Nearly all Insects (except Spiders, and a few others of the apterous tribe, which 

 proceed nearly in a perfect state from the egg) undergo a METAMORPHOSIS, or change 

 at three different periods of their existence. 



The lives of these minute creatures, in their perfect state, are in general so short 

 that the parents have seldom an opportunity of seeing their living offspring. Con- 

 sequently, they are neither provided with milk, like viviparous animals, nor are they, 

 like birds, impelled to sit upon their eggs in order to bring their offspring to perfec- 

 tion. In place of these, the all-directing Power has endowed each species with the 

 astonishing faculty of being able to discover what substance is fitted to afford the 

 food proper for its young; though such food is, for the most /part, totally different 

 from that which the parent itself could eat. Some of them attach their eggs to the 

 bark, or insert them into the leaves of trees and other vegetable substances ; others 

 form nests, which they store with insects <or caterpillars that will attain the exact 

 state in which they may be proper food for their young ones, when they shall awaken 

 into life ; others bury their eggs in the bodies of other insects ; and others adopt 

 very surprising methods of conveying them into the body, and even into the internal 

 'jycera of larger animals. Some drop their eggs into the water, an element in which 

 they would themselves soon be destroyed. In short, the variety of contrivances that 

 are adopted by insects to ensure the subsistence of their offspring, are beyond enu- 

 meration. 



From the eggs of all insects proceed what are called larvce, grubs, or caterpillars. 

 These consist of a long body, covered with a soft, tender skin, divided into segments 

 or rings. The motions of many of the larvas are performed on these rings on)y, 

 either in the manner of serpents, or by resting alternately each segment of the body 

 on the plane which supports it. Such is the motion of the larvae of Flies, emphati- 

 cally so called, and of Wasps and Bees. Sometimes the surfaces of the rings are 

 covered with spines, stiff bristles, or hooks, this is the case in Gad-flies. Crane-flies, 

 and some others. The bodies of the larvae, in some orders of insects, have, toward 

 the head, six feet, each formed of three small joints; the last of which is scaly, and 

 terminates in a hook : this is usual in those of Beetles and Dragon-flies. The larvaa 

 jf Butterflies and Moths, besides six scaly articulated feet, have a variable number 

 of other false feet, which are not jointed, but terminate in hooks disposed in circles 



* The Crab and Lobster tribes form an exception to this rule, for they respire by means of 



*m*. 



f He excepte the Crabs and Lobsters, which he arranges in a class by themselves, and denomi- 

 nates (Testaceous animals. 



