VOLUME 55, NUMBER 1 
19 
toon, approximately 70 miles downstream from the reservoir many species 
of aquatic insects are able to live. Collections from the South Saskatchewan 
River upstream from the reservoir and in the river downstream from the 
reservoir at Saskatoon and at several sites downstream from Saskatoon 
indicate that although H. separata is the dominant net-spinning caddisfly 
species upstream from the reservoir, downstream from the reservoir Sym- 
phitopsyche recurvata (Banks) ( =Hydropsyche recurvata Banks) replaces 
H. separata as the dominant net-spinning species. Temperature is not likely 
the factor causing this change in the abundance of these two species since 
both species do occur upstream and downstream from the reservoir. It is 
more likely that the difference in the turbidity of the water upstream and 
downstream from the reservoir is the major factor affecting the abundance 
of H. separata and S. recurvata in the South Saskatchewan River. The 
collection of H. separata from the White River in Utah by Baumann and 
Winget (1975), the distribution of H. separata in the province of Saskatch¬ 
ewan and the distribution of this species within the South Saskatchewan 
River indicate that H. separata prefers or requires stream habitats where 
the water is very turbid. 
Acknowledgments 
I wish to express my sincere thanks to Dr. D. M. Lehmkuhl for his 
supervision and encouragement during the course of my studies, for making 
available facilities and equipment without which this research would not 
have been possible, for financial support from his National Research Council 
grant and for his constructive criticisms during the preparation of this paper. 
Special thanks go to Dr. Hans Malicky whose many useful comments and 
generous help have aided me in the publication of this paper. I would also 
like to thank Dr. C. Gillott and Dr. L. Burgess for reviewing the manuscript. 
Literature Cited 
Banks, N. 1936. Notes on some Hydropsychidae. Psyche 43: 126-130. 
Baumann, R. W., and R. N. Winget. 1975. Aquatic macroinvertebrates, water quality, and 
fish population characterization of the White River, Uintah County, Utah. Utah Div. 
Wild. Res. 1-55. 
Denning, D. G. 1943. The Hydropsychidae of Minnesota (Trichoptera). Entomol. Amer. 23: 
101-171. 
Lehmkuhl, D. M. 1972. Change in the thermal regime as a cause of reduction of benthic fauna 
downstream of a reservoir. J. Fish. Res. Bd. Canada 29: 1329-1332. 
Malicky, H. 1977. Ein Beitrag zur Kenntnis der Hydropsyche guttata -gruppe (Trichoptera, 
Hydropsychidae). Z. Arbgemein. Osterr. Entomol. 29: 1-28. 
Nimmo, A. P. 1966. A list of Trichoptera taken at Montreal and Chambly, Quebec, with 
descriptions of three new species. Can. Entomol. 98: 688-693. 
Rawson, D. S. 1953. The bottom fauna of Great Slave Lake. J. Fish. Res. Bd. Canada 10: 
486-520. 
