64 



Fresh-water Biology 



PART II 



PRACTICAL EXERCISES IN FRESH-WATER BIOLOGY 



Suit the order to season and weather. 

 Select according to locality and available materials. 

 Repeat when desirable in a new place or season. 

 Permanent records will be of scientific value. 



The text to accompany these exercises is Needham and Lloyd's 

 Life of Inland Water sf^ 



COLLECTING METHODS AND APPARATUS 



For fishes, frogs and salamanders the best collecting methods are those of the fisher- 

 man, who uses nets, seines and traps. His minnow pails and live boxes are also the best 

 means of keeping living material. These have been evolved through age-long experience. 



For the commoner invertebrate animals, nets and retainers 

 of a finer mesh must be used, and special aids for the discovery 

 and manipulation of these smaller forms are desirable. The 

 following are recommended: 



1. An ordinary white enamelled steel vegetable dish about 

 7 X 10 X 2 inches is excellent for examining a fresh catch. When 

 a dip net is dumped into the dish, the animals at once swim or 

 crawl out from the trash and are easily seen against the white 

 background. They can be picked up easily and uninjured on the 

 bug lifter shown in figure 3. 



2. A hand screen such as is shown in figure 4 is the most 

 useful single tool for collecting small animals from rapid streams. 

 It is held in the current by one person while another turns 

 stones on the upstream side. The dislodged insects, etc., are 

 washed by the current upon the screen, which is then lifted 

 from the water. The larger and more conspicuous of them 

 may be picked off by hand; but it is better to dump the catch 

 into a white lined dish, as described above, and then to use 

 a bug lifter. All of them, big and little, may be found in this 

 way. 



Fig. 3. A lifter, made 

 by folding the edges of 

 a rectangular strip of 

 wire cloth, say 3x6 

 inches. The lower edge 

 should be a woven edge. 

 A_ tinner's shears and 

 4-inch folding tongs are 

 the tools needed for mak- 

 ing this and the two next 

 following pieces of appa- 

 ratus. 



* Published by The Comstock Publishing Co., Inc., Ithaca, N. Y. Price $3.00. 



