CHAPTER X 



ANIMAL COMMUNITIES OF THE TENSION LINES BETWEEN LAND 



AND WATER 



I. Introduction 



Margins of bodies of water, swamps and marshes, and temporary 

 ponds are on the border-line between land and water. Swamps and 

 marshes are areas occupied by plants whose stems, leaves, and blossoms 

 are in the air and whose roots are in the water or very moist soil, 

 throughout the year. Areas covered by grasslike plants are commonly 

 called marshes, while those covered by trees are called swamps. 

 Swamps and marshes usually contain water the year round and are 

 commonly either directly connected with some permanent body of water 

 or are fed by springs. Others are dry in summer, and possess an active 

 aquatic fauna only in spring and after heavy rains. Our area, being in 

 a region of glaciation, represents a portion of one of the great marsh areas 

 of the world. Geologically speaking, however, these features represent 

 the positions of lakes and serve to show us the fate of our small lakes 

 and ponds. Classification of these communities is difficult, but they 

 may be divided into temporary and permanent swamps and marshes 

 and into margins of lakes, ponds, and rivers. 



II. Communities 



I. PERMANENT WATER, SWAMP, AND MARSH COMMUNITIES 



a) Lake-margin marsh sub-formation (senescent pond, or emerging 

 vegetation pond association) (Stations 30, 30a, 31). — About the margins 

 of lakes and ponds there is often a girdle of bulrushes and cattails (Fig. 

 116) which has a characteristic animal community. The sub-aquatic 

 stratum is made up of pond animals and has been considered already in 

 chap. viii. There are a few characteristic animals which live chiefly 

 above the water. The diving spider (Dolomedes sexpunctatus) (Fig. 95) 

 crawls about on the marsh vegetation and dives beneath the water for 

 prey. The long slender spider (Tetragnatha laboriosa) is common among 

 the bulrushes (138). At the base of the rushes and sometimes crawling 

 near the top is the snail (Succinea retusa) (91). Common frogs (Rana 

 pipiens and clamata Lat.) (Fig. 116) and the cricket-frog (Acris gryllus) 

 hop about in the water (139). 



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