98 ANIMAL COMMUNITIES OF STREAMS 
REPRESENTATIVE ANIMALS OF A RAPIDS COMMUNITY 
Fic. 47.—An adult brook beetle (Parnidae); twice natural size (original). 
Fics. 48—50.—Different views of the nymph and adult of the May-fly (Siphlurus 
alternatus); 33 times natural size (after Needham). 
Fic. 51.—The eggs of a tabanid fly taken from a protruding stone; twice 
natural size (original). Fic. 52.—Adult fly. 
Fic. 53.—A water-strider (Rhagovelia collaris), from the margin of the swift 
brook (New Lenox, Gaugars); twice natural size. 
Fic. 54.—The common river snail (Goniobasis livescens), covered with calcium 
carbonate secreted by algae; natural size (original). 
Fic. 55.—An intermittent stream sowbug (Asellus communis); twice natural 
size (original). 
