CHAPTER II 



LIFE IN PONDS AND STREAMS 



Ponds. — Small bodies of water are sometimes called ponds 

 and the large ones lakes, but properly speaking a pond as 

 here considered is a body of water which is so shallow that 

 rooted water plants can grow all the way across it. It may 

 be a half mile wide; but it is usually not more than twelve 

 or fifteen feet deep, often less than that. Its waters are so 

 shallow that the bottom is well lighted except where the sur- 

 face is covered by lily pads and duckweeds; but even in such 

 places plenty of light sifts down upon the growing organisms 

 below. Such ponds warm through quickly; an unusually 

 warm winter's day will bring the whirligig beetles up to the 

 surface, and a week or two of spring sunshine will set the 

 whole pond astir. Water and such abundant light and 

 warmth are the only essentials for the growth of diatoms, 

 desmids, and filamentous algse — the great plant crop of the 

 water, the food supply for millions of small animals which in 

 their turn become food for larger ones like the fishes. 



Kinds of ponds. — Many ponds which teemed with life in 

 late winter and spring are dried up and dead looking by 

 August. These transient ponds depend upon the rainfall 

 and the drainage from surrounding hills. They are~ the 

 uncertain ones in which the fairy shrimps appear, and a host 

 of other little crustaceans which can endure months of drought 

 in their "resting egg" stages, insects like caddis larvae which 

 dig down into the bottom mud, and water-bugs which can 



II 



