MATURE COMMUNITIES 



149 



snail {Planorbis trivolvis) (Fig. 112), and the amphipod (Eucrangonyx 

 gracilis) (Fig. 113). All these occur in the senescent stage, where in 

 dry years the pond goes almost dry. The vertebrates of the mature 

 and later stages are not numerous. The fish are limited to mud- and 

 muck-preferring species, the black bullhead (Ameiurus melas) and the 

 mud minnow {Umbra limi) (106). The grass pickerel and the dogfish 

 are found in such vegetation-choked ponds. 





05 



04 ^106""* 



Representatives of the Emerging Vegetation Association (Pond 14) 



Fig. 102. — The common newt (Diemictylus viridescens); natural size (after Hay). 



Fig. 103. — A flat pond snail (Planorbis campanulatus); natural size. 



Fig. 104. — The common pond snail (Lymnaea reflexa) ; natural size. 



Fig. 105. — Small flat snail (Planorbis parvus); 3 times natural size. 



Fig. 106. — A snail (Planorbis hirsutus); 3 times natural size. 



Fig. 107. — A predaceous diving beetle (Cybister fimbriolatus Say) ; natural size. 



Fig. 108. — A soldier-fly larva — unidentified; twice natural size. 



The amphibia are the frogs which occur in all stages of the associa- 

 tion, and the common salamander {Ambly stoma tigrinum), which burrows 

 in the soft mud where it remains during the greater part of the year. 

 It comes out in spring (February or March) and deposits eggs in the 

 pond, where the young are found later. Of the turtles the common 



