A KEY TO THE ENTOMOSTRACA OF COLORADO 



By G. S. Dodds 



Editor's Note. — This study was begun in igo7 when the author was a member of the Faculty of the 

 University of Colorado. During the past three summers Professor Dodds has been in charge of the zoological 

 work at the Mountain Laboratory, Tolland, Colorado. His detailed laboratory studies have been made at 

 the University of Missouri. 



One would not at first thought turn to the semi-arid conditions of 

 the states of the Rocky Mountain region for a favorable opportunity 

 to study aquatic animals. Colorado has, however, proved to be a rich 

 and interesting field for the study of plankton Crustacea. Though 

 there are no large lakes and the total water surface of the state is not 

 great, there exist many small bodies of water — lakes, ponds, and pools 

 — in both plains and mountain areas. These, on account of the wide 

 range of cHmatic conditions found within this area, support an inter- 

 esting and diversified fauna. For this reason, study here is of greater 

 interest than it would be in an area of the same size in the lowlands 

 of the Mississippi Valley. Here is an area especially suited for the 

 study of ecological relations and problems of distribution. 



The data on which the following key is based were, in the main, 

 accumulated during ecological studies of the Entomostraca, the main 

 results of which will appear in a later paper. My collections include 

 material from 124 lakes and ponds, the majority in the mountain 

 region west of Boulder, but some also from stations on the plains. 

 Most of this collecting was done during three summers at the Moun- 

 tain Laboratory of the University of Colorado, at Tolland. I am also 

 indebted for material to Professor Max M. Ellis and Mr. L. C. Bragg. 

 These collections have yielded 55 species. To these I have added all 

 other species known to occur in the state, making a total of 72 species. 

 This list is fairly full, but the collector need not be surprised to find 

 representatives of other species. 



The Entomostraca form a rather poorly defined group, not recog- 

 nized by all authorities, including many of the lower forms of Crus- 

 tacea. Nearly all are of small size. They form by far the greater 



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