DEVELOPMENT OF INSECTS. 95 



It will be necessary to pause here a little, before 

 proceeding to the description and histories of the 

 various insects, because in the course of description 

 certain terms must be used, which must be explained 

 in order to make the description intelligible. 



In the first place, let it be laid down as a definite 

 rule, that 



INSECTS NEVEB GROW. 



Many people fancy that a little fly is only little 

 because it is young, and that it will grow up in pro- 

 cess of time to be as big as a blue-bottle. Now this 

 idea is entirely wrong ; for when an insect has once 

 attained to its winged state, it grows' no more. All 

 the growing, and most part of the eating, is done in 

 its previous states of life ; and, indeed, there are 

 many insects, such as the silkworm-moth, which do 

 not eat at all from the time that they assume the 

 chrysalis state to the time when they die. 



It is a universal rule in nature, that nothing comes 

 to its perfection at once, but has to pass through a 

 series of changes, which if carefully examined can 

 mostly be reduced to three in number. Sometimes 

 these changes glide imperceptibly into each other, 

 but mostly each stage of progress is marked clearly 

 and distinctly. Such is the case with the insect of 

 which we are now considering ; and when we have 

 examined the development of the Tiger-moth through 

 its phases of existence, we have the key to the re- 

 mainder of the insects. 



