Article VIII. — An Entomological Survey of the Salt Fork of the 

 Vermilion River in igji/imth a Bibliography of Aquatic Insects. By. 

 Charles P. Alexander. 



The Salt Fork is the most westerly of the three Illinois branches of 

 the \'ermilion River, and one of the chief affluents of the Wabash from 

 the west. It takes rise in a group of small streams in the west-central part 

 of Champaign county, Illinois, flowing south to Urbana, thence east to 

 near St. Joseph. Near this village the stream takes a large bend and 

 flows southward to near the village of Sidney, after which it flows in a 

 general easterly direction, vmiting with the Vermilion River just west 

 of Danville. The Middle Fork unites with the Salt Fork between the 

 villages of Oakwood and Hillery. 



Originally a clean-water, permanent stream, the Salt Fork was later 

 utilized to receive the sewage and manufacturing wastes of the cities of 

 Urbana and Champaign, with the inevitable consequence that for several 

 miles beyond the Twin Cities the stream became badly polluted and con- 

 taminated to the elimination of a great majority of the less tolerant mem- 

 bers of the original fauna and flora. Thus we have on a small scale 

 almost a duplication of the conditions obtaining in the upper reaches of 

 the Illinois River which receives the sewage of Chicago and cities along 

 its banks. The biological changes that have taken place in the Illinois 

 River as a result of the diversion of the Chicago sewage to this stream 

 twenty-five years ago, have been critically studied and recorded in a 

 series of papers by Forbes and Richardson cited in the general bibliography 

 in the second part of this paper. The Salt Fork stream, flowing close 

 to the University of Illinois, has more recently attracted the attention of 

 local naturalists, and one paper has already been published which is con- 

 cerned with the effects of pollution on its fauna. This ]iaper by Baker 

 (1922) on the molluscan fauna of the Vermilion River and the Salt Fork 

 is of especial value in its particular field in this connection. At the sug- 

 gestion of Dr. Stephen A. Forbes, Chief of the State Natural History 

 Survey, the writer in 1921 attempted to supplement Mr. Baker's studies 

 from a purely entomological view-point. The stream was examined at 

 short intervals, from above the source of ]X)llution near Crystal Lake, 

 Urbana, to just beyond the union of the Salt and Middle forks near 

 Hiller>' in \'crniilion county. Illinois. A total of thirty-three stations 

 were establisl;ed, correspoiiding rather closely with the collecting {)oints 

 chosen by Mr. Baker and with the bacteriological stations of the Illinois 

 Water Survey. The collections of insects taken at the various stations 

 are recorded later in this paper. An effort has been made to decide 

 which of the species may be taken as indicators of the various degrees of 



