INTRODUCTION 



Publication of the following paper, prepared in 1921, setting forth 

 the effects on aquatic insects of the heavy pollution of a small 

 stream by sewage from the twin towns of Champaign and Urbana, has 

 been delayed by deficiency of funds for the printing of articles in the 

 Bulletin of the State Natural Histor\' Survey, preference having been 

 given there to papers of a more immediate importance. 



The recent installation of an adequate plant for the purification of 

 the sewage of these towns before it enters the stream has removed, it is 

 hoped forever, the pollutional conditions here described, and the biologi- 

 cal effects of this renovation can presently be made manifest by a com- 

 parison of the restored insect life of the stream with that here discussed. 

 As an indispensable and irreplaceable basis for such a comparison this 

 paper has acquired a very special value, and fortunately its publication 

 need be no longer delayed. 



A wide-spread campaign, vigorously promoted by the Izaak Walton 

 League, for the sup])ression of stream pollution is stimulating a study 

 of the subject throughout the country, and a carefully prepared bibli- 

 ography appended to this report will doubtless be found useful as a guide 

 to published information, widely scattered as this is in very many jour- 

 nals, American and European. 



Stephen A. Forbes. 



