348 



Crra&trn at fLitural 



Infusory Animalcules, in regard to the num- 

 ber of individuals at any time existing on 

 the earth's surface, which belong to the 

 numerous and diversified races compre- 

 hended in it. In ordinary phraseology, an 

 Insect may be defined as a little animal 

 without bones or cartilages ; furnished with 

 a trunk, or else a mouth opening lengthwise; 

 and with eyes destitute of coverings. This 

 definition will comprehend the whole class 

 of Insects, either with or without wings ; 

 either in their caterpillar or perfect state. 

 Every year adds to the difficulty of de- 

 fining in a brief manner the characters of 

 the great and smaller divisions of the ani- 

 mal kingdom. Hence it will appear, that 

 in this class of animals there are numerous 

 distinctions, and that no general description 

 will serve for all : so various are the appe- 

 tites, manners, and modes of propagation, 

 that every species requires its distinct history. 

 Though so far inferior in point of magni- 

 tude, Insects, it must he confessed, surpass 

 in variety of structure and singularity of 

 appearance all the larger branches of the 

 animal world. The general characters by 

 which they are distinguished from other 

 animals are these : First, they are furnished 

 with several feet : secondly, the muscles are 

 affixed to the internal surface of the skin, 

 which, though hard, sometimes preserves a 

 certain degree of flexibility : thirdly, they 

 breathe, not like the generality of larger 

 animals, by lungs or gills, but by spiracles 

 or breathing holes, distributed in a series or 

 row on each side the whole length of the abdo- 

 men, and communicating with two long air- 

 pipes within their bodies, and a number of 

 smaller ones, to carry the air to every part. 

 The head is furnished with a pair of antennae, 

 or horns, which are extremely various in 

 the different tribes, and which, by their 

 differences of structure, form a leading cha- 

 racter in the institution of the genera into 

 which Insects are distributed. 



Insects have a very small brain, and in- 

 stead of a spinal marrow, a kind of knotted 

 cord, extending from the brain to the hinder 

 extremity ; and numerous small whitish 

 threads, which are the nerves, spread from 

 the brain and knots, in various directions. 

 The heart is a long tube, lying under the 

 skin of the back, having little holes on each 

 side for the admission of the juices of the 

 body, which are prevented from escaping 

 again by valves or clappers, formed to close 

 the holes within. Moreover, this tubular 

 heart is divided into several chambers, by 

 transverse partitions, in each of which there 

 is a hole shut by a valve, which allows the 

 blood to flow only from the hinder to the 

 fore part of the heart, and prevents it from 

 passing in the contrary direction. 



The ancients entertained an idea that In- 

 sects were destitute of jlood ; hence they 

 called them animalia exsanguinea : but now 

 they are well known to be so far from blood- 

 less animals, that in many of them the cir- 

 culation itself of the blood is clearly and dis- 

 tinctly perceived. The blood of Insects 

 differs from that of the larger animals chiefly 

 in oolour, since in most insects it wants 

 redness, being generally of a clear or watery 



aspect, and sometimes of a yellowish hue. 

 The circulation of the blood is particularly 

 conspicuous in Spiders, and in some species of 

 Cimex or bug, especially the Cimex lectu- 

 larius ; it is to be observed, however, that it 

 does not circulate in proper arteries and 

 veins ; but is driven from the fore part of 

 the heart into the head, and thence escapes 

 into the body, where it is mingled with the 

 nutritive juices that filter through the sides 

 of the intestines, and the mingled fluid pene- 

 trates the crevices among the flesh and other 

 internal parts, flowing along the sides of the 

 air-pipes, whereby it receives from the air 

 that influence which renders it fitted to 

 nourish the frame and maintain life. 



The first state in which the generality of 

 Insects appear is that of an egg ; some few, 

 however, are viviparous. From the egg is 

 hatched the Insect in its Larva state ; the 

 Larvae or Caterpillars of Insects differing 

 materially from each other, according to the 

 different tribes to which they belong. There 

 are some Insects, however, which undergo 

 no change of shape, but are hatched from the | 

 egg complete in all their parts, and undergo I 

 no farther alteration than that of casting 

 their skin from time to time, till at length 

 they acquire the complete resemblance of 

 the parent animal. 



Most insects, in the course of their lives, I 

 are subject to very great changes of form, I 

 attended by equally remarkable changes in | 

 their habits and propensities. These changes, j 

 transformations, or metamorphoses, as they ! 

 are called, might cause the same insect, at j 

 different ages, to be mistaken for as many j 

 different animals. For example, a cater- ! 



pillar, after feeding upon leaves till it is fully 



Elace of conceal- j 

 ir-skin, and pre- j 



grown, retires into some place of conceal 



sents itself in an entirely different form, one i 

 wherein it has neither the power of moving ! 

 about, nor of taking food ; in fact, in this, its 

 second or chrysalis state, the insect seems to 

 be a lifeless oblong oval or conical body, 

 without a distinct head, or movable limbs ; 

 after resting awhile, an inward struggle 

 begins, the chrysalis-skin bursts open, and 

 from the rent issues a butterfly, or a moth, 

 whose small and flabby wings soon extend 

 and harden, and become fitted to bear away 

 the insect in search of the honeyed juice of 

 flowers and other liquids that suffice for its 

 nourishment. 



In the different tribes of Insects the Pupa 

 or Chrysalis differs almost as much as the 

 Larva. In most of the Beetle tribe it is fur- 

 nished with short legs : in the Butterfly tribe 

 it is perfectly destitute of all appearance of 

 legs, and has no other motion than a mere 

 writhing when touched : in the Locust tribe 

 it differs very little from the perfect Insect, 

 except in not having the wings complete : 

 and in most of the Fly tribe it is perfectly 

 oval, without any apparent motion, or dis- 

 tinction of parts. The Pupse of the Bee tribe, 

 and other Insects of a similar cast, are less 

 shapeless than those of Flies, exhibiting the 

 faint appearance of the limbs : while those 

 of the Libellulaj or Dragon-flies are loco- 

 motive, as in the Locust tribe, but differ most 

 widely from the appearance of the complete 



