12 ELEMENTARY LESSONS ON INSECTS 



Development. 



The young of stoneflies are called nymphs. They live in 

 streams, where they cling by means of their strong claws 

 to the surface of stones and drift wood (see Fig. 1). When 

 fully grown they climb out of the water upon some exposed 

 surface and shed their old skins and appear as winged aerial 

 adult insects. 



If we compare a stonefly nymph with an adult, we will 

 see that the change in form of body is a slight one, that 

 legs, antennae and tails remain much as before, but that 

 the wings have been enormously expanded and newly 

 articulated at their bases, and now lie folded close upon the 

 back. There has been a development of reproductive ap- 

 paratus on the hindmost abdominal segments, and the 

 gills of the nymph have disappeared, being no longer needed. 



