290 AGRICULTURE. 



II. Metamorphosis, or Development, of Insects. 



All insects develop from eggs, and all undergo 

 a more or less marked change in form during 

 their life-cycle.* 



Many insects when they emerge irom the egg 

 are much like the adult form. These nymphs, 

 as they are called, have no wings. They feed 

 greedily, and as growth demands the hardened 

 skins split and are cast that is, the insects molt. 

 The wings, if wings are present in the adult 

 stage, develop as little pads, which grow larger 

 with each molt until the adult stage is reached, 

 when growth ceases. This method of develop- 

 ment is called incomplete metamorphosis, the 

 three stages of which are egg, nymph, and adult. 

 Common examples of this method of develop- 

 ment are grasshoppers, crickets, plant-lice, and 

 dragon-flies. 



Many other insects, when they leave the egg, 

 differ markedly in form from that of the adult. 

 These caterpillars, grubs, maggots, etc., as the 

 case may be, are called the larva.-. In this larval 

 or second stage they feed, grow, and molt, but 

 do not change their form. When they are full 

 grown they stop eating, become restless, and 

 pass into the third stage of their development 

 (that of the pupa), some attaching themselves to 

 a stick or leaf, others spinning a cocoon, while 



* Those insects belonging to the small order Tliysannrti un- 

 iergo no metamorphosis. 



