THE FARM STREAM 



43 



Fig. 24. The larvae of four two-winged 

 flies {Diptera): a, the swale-fly {Sepedon), 

 withdrawing beneath the surface film of the 

 water; b, the punkie (Ceratopogon); c, the 

 phantom midge larva (.Corethra) ; and d, the 

 common midge (Chironomus), 



the rapids. Note the 

 extent of mud, sand, 

 gravel, rubble, and flat- 

 stone-bottom, and their 

 relation to slope and cur- 

 rent. Note also the 

 physical conditions that 

 organisms have to meet 

 in each situation. 



Collect and examine 

 the commoner plants 

 and animals, first of the 



rapids and then of the still water, omitting the fishes, save, 

 for noting where fishes are seen. 



The Record of this study wUl consist of: 



I. A map, on which are indicated as clearly as possible: 



1 . Waterfalls and riffles. 



2. The extent of each sort of bottom. 



3 . The principal plant beds. 



4. The fish pools. 



II. List of all the water plants observed, arranged in a 

 table with column headings as follows: 



Name (this will be supplied by the instructor). 

 Grows where (that is, in which of the situations examined) . 

 Depth of water (approximate). 



Growth-habit (simple or branched, erect or trailing, stem- 

 less, leafless, etc.). 

 Remarks. 



III. List of all the water animals observed, arranged in a 

 table with column headings as follows: 



Name (this will be supplied by instructor, if needed) . 

 Lives where (in which of the situations examined). 



