1914.] NATURAL SCIENCES OF PHILADELPHIA. 483 



18. The hygrophilous association of the Piedmont Plateau is of 

 relatively subordinate importance owing to the limited extent of 

 permanently moist lands. It is not sharply separable from the 

 dominant mesophilous association. It occurs in stream meadows 

 and small wet areas about springs or in seepage depressions. The 

 associated vegetation consists of hydrophytes and mesophytes with 

 hydrophytic tendencies. 



19. In each of these associations the dominant phase in the Pied- 

 mont Plateau region is the campestral. The sylvan constitutes a 

 relatively insignificant part of the fauna. The removal of the forests 

 and the utilization of the land for farming purposes evidently favor 

 the campestral types, while they restrict the more exclusively sylvan 

 types. 



20. The Orthopteran fauna of the Coastal Plain consists of two 

 widely diverse, but important, constituent associations. One of 

 these is a xerophilous association characteristic of the upland, the 

 other a hygrophilous association characteristic of wet or humid areas. 

 Besides these there is a mesophilous association which, however, is 

 of relatively minor importance. 



21. In contrast with their indefinite character in the Piedmont, 

 the Orthopteran ecological groups of the Coastal Plain are usually 

 quite clearly defined. 



22. The xerophilous association of the Coastal Plain includes both 

 arenicolous and humicolous species. It is typically developed on 

 dry, sandy soils and is associated with a more or less xerophytic type 

 of vegetation. 



23. The hygrophilous association of the Coastal Plain is highly 

 developed. It shows three different types in accordance with the 

 nature of the respective environments. These are: (1) the fresh- 

 water-marsh type, (2) the maritime or salt-marsh type, and (3) the 

 peat-bog type. They are associated with hydrophytic (fresh-marsh 

 type) or zerophytic (salt-marsh and peat-bog types) types of vegetation. 



24. The mesophilous association of the Coastal Plain is typical 

 of rich, loamy soils and is best represented in the productive farming 

 districts of the Middle District. This association tends to invade 

 other districts when these are placed under cultivation. 



25. Primary faunistic subdivisions, or centres of dispersal, of the 

 Coastal Plain are the Coastal and Pine Barren districts; secondary 

 subdivisions, or zones of tension, are the Middle District and Cape 

 May Peninsula. The latter is a minor centre of dispersal for a 

 limited number of southern Orthoptera. 



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