THE INSECTS— ARTHROPODS 



217 



comes like the adult through a series of molts. When a nymph is ready 

 to molt, a fluid will form between the body and the skeleton to separate 

 the two and the skeleton splits down the back to let the insect emerge. 

 It has a soft body covering at this time and swallows air to stretch it 

 while it is hardening. When the new skeleton hardens, which may be 

 within an hour, the insect may be twice its original size and it seems 

 impossible that it could have come from its cast-off exoskeleton. The 

 grasshopper has five molts, but other insects with gradual metamorpho- 



How Insects Live, Wellhouse, F. S. Crofts & Co. 

 Fig. 15.7. Gradual metamorphosis of the grasshopper. 



sis may have as many as twelve. The adult emerges at the final 

 molting. 



The third method of insect development is called incomplete meta- 

 morphosis. This is simliar to the gradual metamorphosis in that the 

 adult is produced after a series of molts of immature stages. The pri- 

 mary difference is that the immature insects with incomplete meta- 

 morphosis live in entirely different condition from their parents and feed 

 in a different manner, with special body parts not possessed by the adult. 

 The immature stages all live in the water and are called naiads. The 

 dragonfly might be mentioned as an example of this type of meta- 

 morphosis. The adult flies in the air, catching other insects for food. 



