BROOK LIFE. 



IS3 



Fig. 124. — A wa- 

 ter-penny. 



The Water-pennies (Field Work). — These are 

 strange larvas, which are rarely recognized as insects 

 by the young collector. They are very flat, circular 

 in outline, and about five sixteenths of 

 an inch in diameter. They are found 

 clinging to the lower surface of stones 

 in rapid streams. Fig. 124 represents 

 one greatly enlarged. They are larvae 

 of beetles of the genus Psephenus (Pse- 

 phe'nus), and are 

 merely mentioned 

 here so that the stu- 

 dent of brook life may know what 

 they are. 



The Dobson or Horned Co- 

 RYDALIS [Field Work). — If a net or 

 a wire screen be held with one 

 edge close to the bottom below 

 some stones lifted with a hoe or 

 garden rake, many of the insects 

 living under the stones will be 

 swept into the net or upon the 

 screen, and can thus be captured. 

 One of the insects that is often 

 caught in this way is the dobson, 

 the ugly creature represented by 

 Fig. 125. 



This larva is well known in 

 many parts of the United States, 

 as it is used extensively by anglers 

 for bait, especially for bass, and in spite of its dis- 

 agreeable appearance it is in some respects very in- 

 teresting to students of Nature study. 



Fig. 125. — The dobson. 



