HOW AN INSECT GROWS UP 



31 



22 times, but most insects molt from three to six times. 

 The intervals between molts are technically called instars; 

 and the larger divisions of the life history that are marked 

 by great changes of form are called stages. The egg is the 

 first stage. 



The second stage comprises a number of instars — five of 

 them in the plant bug shown in the accompanying figure. 

 Differences in size are not 

 shown in this figure (but see 

 figure 19 on page 53) for 

 the smaller are magnified to 

 the size of the larger for easy 

 comparison. The changes of 

 form are slight. Most marked 

 is the development of wings. 

 These appear on the back in 

 the 3d instar, and increase 

 progressively in the 4th and 

 5th. During all this growth 

 period the bug is known as a 

 nymph. 



Then comes the final molting, ushering in the adult stage 

 (6 in the figure). The wings are now fully expanded, covering 

 the body, and capable of flight. The antennae are enlarged. 

 Sex organs are developed. Growth is ended, and the period 

 of reproduction is at hand. . 



The change of form from nymph to adult is often greater 

 than that shown in the plant bug. The nymph of a dragonfly, 



Fig. 12. 



The emergence of a dragonfly from 

 its nymphal skin. , 



