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The objectives of this study were to (1) describe natural variability in retreat and net mesh dimensions and retreat and net tending behavior for the hydropsychid caddisfly Hydropsyche morosa Hagen and (2) perform laboratory experiments to determine the influence of un-ionized ammonia on H. morosa retreat and net construction. H. morosa were collected from fifteen streams in eastern South Dakota and head capsules, nets, and retreats were photographed and measured. Caddis were exposed to 0.00, 0.025, 0.05 and 0.1 mg/L un-ionized ammonia for 48 and 96 hours within experimental stream chambers. Data indicate that exposing caddis to un-ionized ammonia caused them to change their net/retreat construction and tending behavior. Net mesh variability increased 123% in 0.025mg/L and 227% in 0.05 mg/L treatments relative to controls. Net and retreat dimensions in experimental streams also demonstrated significantly greater variability when compared to nets collected from reference streams, indicating a container effect. Behavior in treated chambers was slower and more lethargic when compared to control chambers. Results suggest that un-ionized ammonia influences H. morosa’s construction abilities and behavior, most notably in net mesh and retreat dimension variability.

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Proceedings of the South Dakota Academy of Science



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