WHAT AN INSECT IS LIKE: INSIDE 



23 



three flat, vertically placed gill plates at the end of the 

 body, slowly swinging these from side to side. 



2. Mayfly nymphs, that swim with up and down un- 

 dulations of the abdomen and of the three fringed 

 tails at its tip, aided by backward strokes of the 

 paired gills on the first seven abdominal segments. 



3. The worm-like, pale cylindric larvae of midges, that 

 swim by figure-of-8 loopings of the body. 



\ct 



Fig. 8. — The young of three insects that are suitable for micro- 

 scopic examination as transparent objects. A, a mayfly nymph; 

 B, a midge larva; C, a damselfly nymph. 



