The principal nuisance species of caddisflies at Keokuk, Iowa, are Hydropsyche orris Ross, Cheumatopsyche campyla Ross and Potamyia flava (Hagen), all members of the family Hydropsychidae (Order Trichoptera). The larvae of these species require considerable water current so that food may be carried into the nets which they construct upon submerged rocks and other silt-free structures. Keokuk lies along the tailwaters of the largest dam on the Upper Mississippi River, and the current and subsequent lack of silting create a large area which is favorable for hydropsychid larval habitation. Consequently, Keokuk is host to more caddisflies than the other river cities.
H. orris larvae build rigid catching nets and are most abundant in the fastest currents. C. campyla larvae construct loose, voluminous nets and are most abundant in the tailwaters and other areas where the current is moderated. P. flava larvae also build loose nets, but they are found most frequently in the rock and sand areas of the main channel of the river. Hydropsychid larvae are capable of populating areas by drifting with water currents.
Fremling, Calvin R.
"Biology and possible control of Nuisance Caddisflies of the upper Mississippi river,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 33
, Article 1.
Available at: https://lib.dr.iastate.edu/researchbulletin/vol33/iss483/1