374 
IOWA ACADEMY OF SCIENCE 
CONOIiUSIONS. 
In the opinion of the writer the most significant facts brought 
to light by this study of the animal life of the brook are these : 
(1) the wonderful variety and complexity of the fauna in a 
habitat that does not remain constant throughout the year ; and 
(2) the dovetailing interdependence of each species upon others 
in the environment, the number of individuals in each case de- 
pending primarily upon the food supply, which ultimately re- 
verts to the amount of plant life. 
BIBLIOGRAPHY. 
The following list of references is by no means complete. A 
catalogue of the published papers on May flies alone, for ex- 
ample, would fill many pages. It is the intention of the writer 
to list but a few works, most of which are general in nature, 
that may be helpful to beginners in this field. 
Adams, Chas. C.: Guide to the Study of Animal Ecology, 183 pp. 
Macmillan, 1913. 
Shelford, V. E.: Animal Communities in Temperate America, 362 pp. 
University of Chicago Press, 1913, or Bulletin No. 5, 
The Geographic Society of Chicago. 
Needham, MacGillivray, Johannsen, Davis; Aquatic Insects in New 
York State, 517 pp. Bulletin No. 68, New York State 
Museum. 
Miall, L. C.: The Natural History of Aquatic Insects, 395 pp. Mac- 
millan, 1895. 
Emerton, J. H.: The Common Spiders of the United States, 225 pp. 
Ginn and Company, 1902. 
Call, R. E.: A Descriptive Illustrated Catalogue of the Mollusca of 
Indiana, 198 pp., 78 plates. 24th Annual Report of 
the Department of Geology and Natural Resources, 
1899. 
Comstock, J. H., Comstock, Anna B.: Manual for the Study of In- 
sects, 701 pp. Comstock Publishing Company, 1912. 
Blatchey, W. S.; Coleoptera of Indiana, 1385 pp. Nature Publishing 
Company, Indianapolis, 1910. 
Morgan, Anna H.; A Contribution to the Biology of May Flies, 42 
pp., 13 plates. Annals Entomological Society of Ameri- 
ca, Vol. VI, September, 1913. 
Malloch, J. R. : American Black Flies or Buffalo Gnats, 71 pp., 6 
plates. Bulletin No. 26, Technical Series, U. S. Dept. 
Agri., Bureau of Entomology. 
Laboratories of Animal Biology, 
State University of Iowa. 
