An Associational Study of Illinois Sand Prairie

The present study is restricted to the grassland associations of sand in the Illinois River valley, and the emphasis is placed upon the animals of the region. The unit of study is here the association, or community of organisms: the social aggregateof plants and animals, which, living in a common environment, come into various relations one with another. In the sand prairie of the river valley several types of areas may be distinguished, eachcharacterized by a definite set of physical conditions, by a particular association of plants, and by a particular assemblage of animals. Inthis report the plant and animal assemblages are considered together, and inquiry is made into the relations which obtain between them, and between them and the physical environment.