INTRODUCTION. 5 



mouths, but through Httle holes, called spiracles, generally nine 

 in number, along each side of the body. Some, however, have 

 the breathing- holes placed in the hinder extremity, and a few 

 young water-insects breathe by means of gills. 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 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 spontaneous- 

 ly generated from putrid animal or vegetable matter. A few in- 

 sects, 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 imme- 

 diately 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 in- 

 sect, at different ages, to be mistaken for as many different ani- 

 mals. For example, a caterpillar, after feeding upon leaves till it 

 is fully grown, retires into some place of concealment, casts off 

 its caterpillar-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 in- 

 sect seems to be a lifeless oblong oval or conical body, without 

 a distinct head, or movable limbs ; after resting awhile, an inward 



