420 GENERAL BIOLOGY 



Study 57. Field observations on diving beetles. 



Apparatus needed : Dip nets and beakers or other small 

 vessels for individual use. A seine may be useful for obtain- 

 ing greater numbers of the larger forms that live farther 

 from shore (Dytiscus, etc.) 



If the student will carefully gather his own material for 

 the studies of this subject, he w^ill see much that is of interest 

 in the manner of life of these beetles, and some things that 

 will aid in understanding the structural peculiarities of some 

 of them, to be worked out later (in study 58). It must not 

 be forgotten for a moment that all peculiarities of vital 

 importance are related to environment. 



The best collecting grounds are ponds; small ponds if 

 permanent, even though they be shallow. Few beetles will 

 be seen anywhere without special search for them; a few 

 may be seen rising to the surface to take air, and immediately 

 descending again. It will require careful collecting, and 

 discrimination as to species, to get a goodly variety. Begin 

 by "sweeping" the submerged vegetation at the farthest 

 reach of the net for the larger species, and work gradually 

 toward shore. The smallest species (Bidessus, etc.), will 

 be found right at the edge of the water, and will be obtained 

 by scraping the bottom close up to the bank. Learn care- 

 ful collecting: for it is a most important part of the education 

 of a naturalist. 



Dip up and examine the trash that lies on the bottom; 

 examine also, floating vegetation. 



Note the favorite location of each species: the center of 

 its abundance. Observe the relation between size of the 

 species and the depth of the water dwelt in . Observe how the 

 jumping species gather about floating trash, which 

 furnishes a support from w^hich a jump in the air can be 

 made. Such things are best seen before the water has 

 been too much disturbed with nets. 



