Variations in Abundance of Certain Invertebrates in William Trelease Woods, 1933-1938

Abstract

This paper differs from several others on the same area in that it proved possible to trace variations in abundance (annuation) for five consecutive years for several species and for four years for a larger number. Some effort was made to trace changes from season to season (aspection) and some results were worthy of record. The difficulties encountered made possible a statement of the best methods to follow. Several community studies have been made at the University of Illinois, largely in the two woodlands owned by the University and known as William Trelease Woods (formerly University Woods) and Brownfield Woods. McDougall (1922) has given an account of the plants in William Trelease Woods, and in 1928 he and Penfound made a further report upon the plant forms there. Weese (1924) studied the invertebrates in this woodland during 1921-1922. Several later workers have considered various phases of the community problem. Blake (1926) gave an account of hibernation among invertebrates, based on his observations made during the winter of 19241925. In a later paper (1931) he considered the spring population of 1925. Rutherford (1929), working in Brownfield Woods, studied the movements of insects in hibernation. Smith-Davidson (1930) reported upon the treelayer society in both Brownfield and William Trelease Woods, a phase heretofore neglected. Her later paper (1932) gave an excellent account of seasonal variability and its effect upon total populations as seen in 1925-1926. In 1933 studies of the animal community at William Trelease Woods were begun in the desire to have continuous records of animal populations over a period long enough to indicate the reactions of the animals to weather changes. Collections of invertebrates from 1933 to 1935 were made by Rice (1944) and were continued from 1935 to 1936 by Kanatzar, who prepared a master's thesis which was not published. The writer's work began in the fall of 1936 and continued until Septembet, 1938. Rice (1946) tested the methods used and analyzed the populations of forest species with reference to weather and bird predation. Her work began October 1, 1934, and ended with September, 1935. However, she made use of Kanatzar's data through November, 1935, and began her most serious analysis with November 1, 1933, and ended with October 31, 1935. It was possible for the writer to report on nine species through the entire period, on six species through Kanatzar's period of study, and two species through Rice's period of study with Kanatzar's year omitted. Only one species analyzed by Rice was graphed by the author and this for a different purpose.