INTRODUCTION. 5 



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 blood, which is a 

 colorless or yellowish fluid, does not circulate in proper arteries 

 and veins ; but is driven from the forepart 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 penetrates 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. 



All insects are produced from eggs, and none are spontaneously 

 generated from putrid animal or vegetable matter. A few insects, 

 such as some plant-lice, do not lay their eggs, but retain them 

 within their bodies till the young are ready to escape. Other 

 .insects invariably lay their eggs where their young, as soon as 

 they are hatched, will find a plentiful supply of food immediately 

 within their reach. 



Most insects, in the course of their lives, are subject to very 

 great changes of form, attended by equally remarkable changes in 

 their habits and propensities. These changes, transformations, or 

 metamorphoses , as they are called, might cause the same insect, at 

 different ages, to be mistaken for as many different animals. For 

 example, a caterpillar, after feeding upon leaves till it is fully 

 grown, retires into some place of concealment, casts off its cater- 

 pillar-skin, and presents itself in an entirely different form, one 

 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 dis- 

 tinct 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. 



