This is the fifth revision of this little book. Its purpose remains the same as that of the earlier editions: to facilitate the recognition of fresh-water organisms both in the field and laboratory. The format remains the same as the earlier editions in offering keys, tables, and figures illustrating mostly genera and in a few cases, species. Only organisms commonly found in fresh waters are included. Inhabitants of salt, brackish, and alkaline waters are omitted. Vascular plants are also omitted. Generic names are applied in an inclusive sense to groups of species that a beginner may be able to recognize by external differences.
The principal change in this edition has been to add the fishes. Keys to the most common forms caught by anglers are presented along with four new plates covering both structures and some 65 different kinds. New plates of protozoans, water bugs, caddis-worm houses, and aquatic beetles are also presented. Numerous revisions have likewise been made in all of the keys.
New materials have been added on the following items: caring for field collections, methods of taking quantitative stream and lake bottom samples, the quantitative distribution and abundance of stream dwelling organisms, methods of making analyses of water for oxygen, carbon dioxide, alkalinities, and the determination of pH values. In addition, references are given to many new books and papers that have appeared since publication of the fourth edition.
For much generous aid in making the revisions, I wish to thank the following colleagues: Dr. William Balamuth (protozoans), Dr. Frank Cole (Diptera), Mr. W. C. Day (mayflies), Dr. D. G. Denning (caddisflies), Mr. W. I. Follett (fishes), Dr. John G. Gallagher (rotifers), Mr. Stanley Jewett (stoneflies), Mr. Hugh B. Leach (aquatic beetles), Dr. Milton C. Miller (crustaceans), Dr. G. F. Pappenfuss (algae), Mr. Allyn G. Smith (molluscs), and Dr. R. L. Usinger (aquatic true-bugs).
I am especially indebted to Mrs. Emily Reid for making the many new drawings required. To Miss Pauline Shorb I owe much for her meticulous care in both typing and proofreading. Graduate student Robert Behnke provided fine assistance in proofreading. Any errors that may be found are solely the fault of the writer.
Observation of aquatic organisms in their natural settings is essential to accompany indoor work on finding out their names. It is simple and easy to tell a mayfly nymph from a stonefly nymph or a water beetle larva from a caddisfly larva. Users of this book should not let the lack of common names, nor the somewhat awe-inspiring scientific names, delay their progress in acquiring a . . .