1 92 Nature- Study Agriculture 



Am. Mus. Nat. Hist. 



FIGS. 144 and 145. Stages in the life of the common house fly or filthy fly : 

 Fig. 144, eggs of fly. They hatch in about 12 hours. Fig. 145, larva of fly. 

 The larvae (maggots) retain this form for about 5 days, during which they are 

 very active. 



144, 145, 146, and 147). Some insects look as different 



in successive stages as if they were different animals. 



Thus the caterpillar becomes in time a chrysalis and 



after that a butterfly. Such change from one form into 



another is called " metamorphosis." (Exp. i.) 



Life history Some insects change very little and are said to undergo 



g rass . incomplete metamorphosis. The grasshopper is such 



hopper; an i nse ct. It comes from the egg looking so much like 



incomplete 



metamor- an adult grasshopper that no one would mistake it for 



phosis an y otner i nsec t. it has no wings, however. It eats 

 hungrily at this time, and whenever its skin becomes too 

 small for its growing body it molts, coming forth in a new 

 and larger skin. Its wings begin to develop, and they 

 become longer at each molt. Five times the skin is 

 cast, splitting down the back and allowing the insect to 

 crawl out. In its incomplete stage the insect is called 

 a " nymph," to distinguish it from the full-grown adult. 

 At the fifth molt the grasshopper emerges from its cast- 

 off skin with a full-grown pair of wings. 



When an egg of a butterfly hatches, we have no butterfly 



