INSECT ECOLOGY 389 



IV. CLASSIFICATION OF ENVIRONMENTS 



The distinction must be made between climatic environmental 

 :omplexes and local complexes. "The climate, and such features as 

 types of vegetation covering large areas, e.g., steppe, deciduous forest, 

 etc., are commonly regarded as climatic. Opposed to these, and lying 

 within them, are the local conditions, such as streams, lakes, soils, 

 exposure, etc., which are only indirectly dependent upon climate." 

 (Shelford.) 



The classification of animal environments is based upon vegetation, 

 physiography, or both. Where vegetation exists, animal communities 

 are referred to the plant communities which form their environments. 

 (Plate V.) 



The simple and natural classification of plant communities recom- 

 mended by Livingston and Shreve is illustrated as follows: 



"The extensive areas such as the sagebrush plains of the Great 

 Basin, the grasslands of Nebraska and Kansas, or the pine forests of 

 .the Atlantic Coastal Plain are designated as formations. The smaller 

 and less markedly differentiated areas within a formation are designated 

 as associations, as, for example, the forests of shortleaf pine in New 

 Jersey, those of loblolly pine in Maryland and Virginia, and those of 

 longleaf pine in the Gulf States, all lying within the Coastal Plain 

 formation. The smallest units of vegetation are [sometimes] termed 

 societies, and these are of small area and represent portions of the associa- 

 tion in which a definite aggregation of species is to be found." (Living- 

 ston and Shreve.) 



An outline of the content of animal ecology prepared by a committee 

 of the Ecological Society of America, in 1920, contains the following 

 useful synopsis. 



DISTRIBUTION OF COMMUNITIES 

 i. Land communities. 



(a) Forests with broad thin leaves. 



1. Continuously moist and evergreen. 



(a) Uniformly warm, affording habitats in six or more strata. (Tropical 



rain forests.) 

 (6) With cool season. (Temperate rain forests.) 



2. Intermittently dry or cold, and deciduous. 



(a) Warm with distinct dry season. (Tropical deciduous forest.) 



(b) With cold winter, little winter shelter. (Temperate deciduous forest.) 

 (6) Communities of evergreen forests of narrow, thick leaves. 



11. Moist conifer forest with little undergrowth. 

 2. Rainy conifer forest with shrub undergrowth. 

 3. Open, arid, conifer forest. 



