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Behavior of Pycnopsche (Trichoptera: Limnephilidae) on Mineral Substrates in Laboratory Streams

MacKay, Rosemary J.
Ecology 1977 v.58 no.1 pp. 191-195
Limnephilidae, burrows, estivation, gravel, instars, larvae, sand, streams, woodlands
Three species of Pycnopsyche larvae were given a choice of mineral substrates ranging from medium sand to small pebbles in laboratory streams. Pycnopsyche luculenta avoided depositing substrates and remained on or near firm, smooth surfaces. Pycnopsyche gentilis also avoided depositing substrates except during a short period in the fifth (final) instar when leaf—disc cases were transformed to sand—grain cases of particles 1—2 mm in diameter. Mature larvae of P. scabripennis burrowed into gravel particles 4—16 mm in diameter for a 3—mo aestivation period. Apart from the short—term selective behavior of P. gentilis and P. scabripennis, all species responded positively only to organic substrates and showed no mineral substrate selection that was concordant with larval distribution in a woodland stream. Only those species which use mineral particles for cases or burrows demonstrated a size preference. The very precise size of particles selected by aestivating P. scabripennis larvae may be an important limiting factor for this species.