170 IOWA ACADEMY OF SCIENCES 



PRELIMINARY NOTES ON THE IOWA ENTOMOSTRACA. 



BY L. S. ROSS. 



The careful work done by a few investigators has shown the 

 relation existing between our common fresh water fish and the 

 minute Crustacea of the streams and lakes. The results of 

 these investigations prove the importance of the Entanostraca 

 as a source of food supply for the young fry of many species, 

 and even for the adults of some. The most extensive work 

 upon this subject is that done by Dr. S. A. Forbes of the Uni- 

 versity of Illinois. An account of the methods pursued and of 

 the results obtained is given in the bulletins of the Illinois State 

 Laboratory of Natural history; Bulletins Nos. 2, 3 and 6, and 

 articles VII and VIII, Vol. II. 



Since the young fish depend for subsistence, to such an 

 extent, upon the relative abundance or scarcity of the Entom- 

 ostraca, it becomes a question not only of scientific interest, 

 but of economic importance to learn concerning the distribution 

 and abundance of the various species of this group of our fresh 

 water fauna. The knowledge of the vertical distribution of 

 different species in the lakes is of importance because some 

 species of fish feed at one level and some at another. Some 

 have their favorite haunts among the weeds of the shallows, 

 others in the clearer, deeper waters. 



Consideration of these facts induced me to begin work upon 

 the occurrence and distribution of Entomostraca in the state 

 of Iowa. The paper presented is a report of work begun, 

 rather than work completed. 



In order to combine pleasure with business, I decided to 

 make a bicycle journey to the lake region of Iowa. In the first 

 part of August of the past year, Mr. McCormack of Drake Uni- 

 versity, and myself started across country en route for Lake 

 Okoboji. We carried vials of alcohol and a coarse and a fine 

 net; the latter being of bolting cloth. The streams did not 



