THE FARM STREAM 



39 



be seen without a 

 lens and too num- 

 erous even to be 

 mentioned here. 

 The water is like 

 another world of 

 life, containing a 

 few forms that are 

 directly useful to 



Fig. 21. Adult aquatic insects: 



the back-swimmer 

 US and many more i No '? n f c ' a }i b -^ c .water-boatman (Corcra); c, a diving- 

 J beetle (Dyttscus) ; a, a giant water-bug (Benacus). 



that furnish for- 

 age for these; containing a few that are noxious when 

 adults, such as black-flies, horse-flies and mosquitoes, and a 

 host of other forms, all of interest to the naturalist, but not 

 known to be of practical importance. They are all a part 

 of the native population of the stream, and each has a share 

 in carrying on its natural social functions. 



In the water as on land, green plants represent the great 

 producing class, while animals and parasitic plants are the con- 

 sumers. And among 

 the animals there 

 are herbivores and 

 carnivores, parasites 

 and scavengers. 



One who but casu- 

 a 1 1 y examines the 

 animal life of the 

 stream is apt to see 

 chiefly carnivorous 

 forms; for these are 

 most in evidence: 



Fig. 22. Aquatic insect larvae: a, a diving-beetle, anQ nere, aS eiSe- 



Coptotomus (after Helen Williamson Lyman); b, a _-t.„_„ liot-Ki'wvfoe 



dobson larva, or hellgrammite, Corydalis cornuta (after wiJ-cie, iiei Ulvurca, 



Lintner); c, an orl-fly larva, Sialis (after Maude H. t. . ; _ _ ^„^„1„ 



Anthony). Demg poorly 



