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Article by Calvin R. Fremling, in the September 1960 issue (number 483) of Research bulletin / Agriculture and Home Economics Experiment Station, Iowa State University of Science and Technology. The article and issue are complete. Fremling is noted as being "Formerly graduate assistant, Department of Zoology and Entomology, Iowa State University of Science and Technology. Now assistant professor of biology, Winona State College, Winona, Minnesota." The article covers caddisflies found on the upper Mississippi River. Contents: - Summary - Introduction - Caddisfly abundance in Keokuk - Description of the adults - Behavior of the adults - Oviposition - Larvae - Hatching and early distribution - Case and net construction - Ecological distribution of larvae - Larval feeding behavior and growth - Pupae - Generations per year - Caddisfly control - Adulticides - Light traps - Changes in street and store lighting - Larvicides - Literature cited Summary [page 856]: "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. Ovipositing females of the three species were collected beneath the surface of the water with an underwater light trap. P. flava females were collected as deep as 20 feet and H. orris and C. campyla as deep as 12 feet. Females may re-enter the water several times, and emergence traps captured many more females than males. Experiments with a vertically floating pole indicated that oviposition was most concentrated at a depth of 3 to 4 feet. C. campyla and P. flava oviposition was observed in the laboratory, where adult females were seen to remain submerged for several hours. An analysis of the numbers of caddisflies which were captured nightly at a downtown cafe window indicated that H. orris, C. campyla and P. flava are bivoltine species, reaching peaks of abundance in early and late summer. Size-frequency distributions of H. orris larvae collected from navigation buoys also indicated that H. orris completes two generations per year. C. campyla adults were reared from eggs in 51 days in the laboratory. A blacklight trap was developed and may serve as a caddisfly abatement device at Keokuk. Insecticide space sprays applied to H. orris swarming areas hold promise, as do residual sprays applied to riverside foliage where the caddisflies rest during the day. H. orris caddisflies were shown to be vulnerable to four organic phosphorus insecticides. Of these, malathion is the most lethal. Granular larvicides applied to the tailwaters may control local larval populations temporarily. Low solubility of the granular formulation may prevent injury to fish. A loss of caddisfly larvae in the tailwaters should affect the fish very little since fish scarcely utilize the hydropsychid caddisfly larvae in this area." 26 pages. Part of the Cal R. Fremling Collection.

Publication Date





Winona, Minnesota


Biologists; Insects Behavior; Mayflies; Caddisflies


Special Collections-Library



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Requests to reproduce this image must be granted by the Winona County Historical Society.

Contributing Institution

Winona County History Center

Master File Format


Scanning Responsibility

Northern Micrographics

Date Digital

2019-06-24 00:00

Metadata Creation Responsibility

Anna Gaffey

Unique Identifier


Biology and Possible Control of Nuisance Caddisflies of the Upper Mississippi River



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