Leaf inputs in temperate forest streams may limit caddisfly production because leaf detritus serves both as a food and case-material resource. We estimated Pycnopsyche gentilis production in a stream experimentally decoupled from its riparian habitat and a reference stream for 8 y in the southern Appalachians. We also examined laboratory survivorship, growth, and case-building activities of P gentilis in substrate containing various quantities of leaf material. Pycnopsyche gentilis production declined to 0 within 3 y of the start of litter exclusion. Abundance, biomass, and production of R gentilis were positively related to leaf litter standing crops. Maximum individual length of P gentilis was reduced when annual leaf standing crops fell below 25 to 50 g AFDM/m(2). Observations of case construction for instars removed from their original leaf cases and kept in substrate with low leaf standing crop, showed that P gentilis was capable of rebuilding a case of available substrate and surviving for 3 to 4 wk before dying of starvation. Survivorship and growth were significantly greater for larvae reared at high and intermediate leaf standing crops, than at low leaf standing crop. Older instars had higher survivorship rates but lower growth rates than younger instars in the low litter substrates. Survivorship and growth rates were lower for some individuals forced to rebuild new cases, indicating an energetic cost associated with case-building activities. Our results demonstrate that the linkage between terrestrially derived organic matter and production of a caddisfly shredder was a consequence of food availability.
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