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ZOOLOGY. 



minute, wingless insects which do not undergo any metamorphosis. The 

 body is covered with scales or hairs. The spring-tails and snow-fleas are 

 examples. These make their leaps by suddenly straightening out a tail- 

 like structure which is bent under the body when at rest. They are not 

 the only wingless insects and hence the name is somewhat misleading. 

 See Fig. 1.36. 



FIG. 136. 



FIG. 136. Campodea, a Thysanuran. Magnified 30 times. By J. W. Folsom. 



Questions on the figure. In what respects does this form seem inter- 

 mediate between the Myriapods and the higher insects? How does this 

 compare with the larvae of insects which undergo a metamorphosis? Can 

 you distinguish head, thorax, and abdomen? 



Order Orthoptcra (straight wings). In this order the metamorphosis 

 is incomplete or lacking. There are usually two pairs of wings, the an- 

 terior often somewhat thickened, serving as a cover for the posterior. 

 Mouth parts are adapted to biting and chewing. Here belong the cock- 

 roaches, grasshoppers, crickets, locusts, katydids, walking-stick insect. 

 The order is of considerable economic importance. Most of its members 

 are vegetable feeders and when they are gregarious are often very de- 



