INSECTS 



81 



FIG. 136. Measuring worm, 

 the larva of a moth. 



stages : (i) egg, (2) larva, (3) pupa, and (4) imaga, or per- 

 fect insect (Figs. 136, 137, 138). 



The egg stage is one of development, no nourishment 

 being absorbed. The larval stage is one of voracious feed- 

 ing and rapid growth. In the pupa 

 stage no food is taken and there is 

 no growth in size, but rapid devel- 

 opment takes place. In the per- 

 fect stage food is eaten, but no 

 growth in size takes place. In this 

 stage the eggs are produced. When 



there is very little resemblance between the 

 larva and imago, and the pupa is quiescent, 

 the metamorphosis, or change, is said to be 

 complete. When, as with the grasshopper, 

 no very marked change takes place between 

 the larva and imago (that is to say, during 

 the pupa stage, which is active), the meta- 

 morphosis is said to be incomplete. By 

 studying the illustrations and specimens, and by thinking 

 of your past observations of insects, determine which of the 

 insects in the following list have a complete metamorpho- 

 sis : beetle, house fly, grasshopper, butterfly, cricket, wasp. 



b 



& 



FIG. 137. Pupa 

 of a mosquito. 



FIG. 138. THE FOUR STAGES OF A BOTFLY, all enlarged. 



a, egg on hair of horse (bitten off and swallowed) ; 3, larva; c, larva with hooks for holding 

 to lining of stomach; d, pupal stage, passed in the earth; e, adult horse fly. 



