62 ELEMENTARY LESSONS ON INSECTS 



mating and egg-laying. Feeding and growth are the business 

 of the nymphs: provision for posterity is that of the adults; 

 and these two major functions of all living things are in 

 mayflies sharply separated. 



The living material, available during the school year, will 

 be mainly aquatic nymphs. These abound in all fresh waters 

 and are easily collected. They may be at once distinguished 

 from all other animals by the presence of paired leaflike 

 gills upon the back of the abdominal segments. There are 

 three principal forms of mayfly nymphs: 



1. Climbing forms , such as shown in figure 8A. These are 

 mainly pond species, found climbing among water weeds. 

 They are easily taken with a dip net. 



2. Burrowing forms, that live in the bottom mud, es- 

 pecially where it is somewhat sandy (see fig. 21). These 

 may be scraped up and sifted out from the mud with a sieve 

 net. 



3. Close-clinging forms, that live in moving waters, in 

 rapids of streams, or on lake shores. They are very flat and 

 lie with legs outspread upon the surface of submerged rocks 

 or logs. When a stone is quickly lifted from the rapids and 

 turned over they appear almost as if engraved upon its 

 surface; they may then be picked from the stones by hand. 

 They soon die for lack of air if kept in still water; and are 

 best carried to the laboratory in so very small amount of it 

 that they are partly exposed to the air in transit. They may 

 be kept alive only in running water. A cage of the form 



