8 NATURE AND RELATIONS OF BIO-ECOLOGY 



actual survey was carried out by Ruthven upon this broad basis and 

 led to the conclusion that the hardwood forest represents the climax 

 of the region, its habitat increasing at the expense of other societies so 

 that the associated biota tend to become general for the area. Later, 

 a more extensive investigation of Isle Royale was made by Adams 

 and his co-workers, utilizing the same methods (1909). Even greater 

 attention was paid to succession, though this was treated separately 

 with respect to the four animal groups, viz., invertebrates, beetles, 

 birds, and mammals. The biological survey of a sand-dune region 

 in Michigan followed the same general plan (Ruthven, 1911). 



In a bibliographical treatise Adams presented the conclusion that 

 such projects should deal with the balance within the entire biotic 

 community. It was stated that for any comprehensive study it is 

 necessary to determine the biotic base or optimum toward which con- 

 ditions tend and at which equilibrium occurs. Some uncertainty exists, 

 however, as to the author's use of the term biotic, since he speaks of 

 all this as providing the best method of studying the animals of a 

 region. IMoreover, in the ecological investigation of prairie and forest 

 invertebrates (Adams, 1915) , the animals were treated as separate 

 and the plant associations considered as furnishing the environment 

 for them. 



Shelf ord (1907-1913). In a preliminary survey, Shelford (1907) 

 traced the relation of Cicindela to the succession of plant commu- 

 nities. The distribution of eight species of tiger beetles was in close 

 correspondence with the zoned habitats and communities, and the 

 conclusion was reached that a similar harmony existed with respect 

 to the fauna in general. 



In a series of five articles on ecological succession, the same author 

 elaborated the developmental relation between plant and animal com- 

 munities (1911-1912). These were stated to be very generally in 

 agreement. Disagreement was said to be temporary, and to accom- 

 pany rapid successional changes. Succession was stated to be due to 

 an increment of changes in conditions produced by the plants and 

 animals living at a given point. 



In the treatment of the animal communities of eastern North Amer- 

 ica (1913, a), this theme of the interaction of the two groups of 

 organisms was further developed. Several of the communities were 

 designated by means of a prevalent or characteristic animal and one 

 or more plant dominants, though in general plant communities were 

 treated as constituting the habitat for animal ones. Thus were distin- 

 guished a white tiger beetle or cottonwood association, an ant lion or 

 black oak, a Hyaliodes or black oak-red oak, a green tiger beetle or 

 white oak-red oak-hickory, and a wood frog or beech-maple associa- 

 tion. Succession was emphasized as the chief principle underlying 

 the relations of communities. Plants were recognized as the dominant 

 sessile forms of the land, while animals were considered to be the 

 chief members of the successions in streams, and the primary nature 

 of the climax was stressed. 



Shelford further endeavored to correlate the l)ehavior of the ani- 

 mal constituents with the life forms of the plants. The terminology 



