THE FARM STREAM 



39 



Fig. 21. Adult aquatic insects: a, the back-swimmer 

 (Nolonecta); 6, the water-boatman (Corixa); c, a diving- 

 beetle (Dytiscus); d, a giant water-bug (Benacus). 



be seen without a 

 lens and too num- 

 erous even to be 

 mentioned here. 

 The water is hke 

 another world of 

 life, containing a 

 few forms that are 

 directly useful to 

 us and many more 

 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 natiu-al 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 i n evidence : 

 ^ and here, as else- 



Co'^to/omus (after 'Helen Wiiliamson Lyman) • fc a .^^^.U^^p hplbivorCS 



dobsun larva, or hellgrammite. Coryda/ts cor«M<a (after WncrC, nClDlVOrtb, 



Lintner); c. an orl-fly larva, Sialis (after Maude H. U f^ \ ^ „ nnnrlv 



Anthony). UClUg puoiiy 



Fig. 22. Aquatic insect larvae: a, a diving-beetle 

 Co^to^omus (after Helen Williamson^ Lyman) ; fc_. 



