Life history and production of Goerita semata Ross (Trichoptera: Limnephilidae) in the southern Appalachian Mountains

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Abstract
In western North Carolina, populations of Goerita semata are restricted to moss- or livewort-covered rock faces located in small, heavily shaded high-elevation streams. The larval developmental period was completed in about 655 days with two distinct cohorts being present at any time. Growth was slow, averaging only 0.71% ash-free dry mass per day, with the highest growth rate of 1.52% per day measured for fifth instar larvae between March and April. Weight losses occurred in overwintering larvae. In spite of low growth rates, relatively high production (including silk expenditure) was maintained by high larval densities (mean = 288 .cntdot. m-2). Production in the rock-face habitat was 237.66 mg ash-free dry mass .cntdot. m-2 year-1 or 47.53 mg ash-free dry mass .cntdot. m-2 .cntdot. year-1 when weighted by areal proportion of rock-face substrate for the entire stream. Most growth occurred during the spring when fifth instar larvae accrued > 50% of the definitive larval weight. This period of enhanced growth was correlated with increases in water temperature and in diatom consumption by the larvae. During the spring, diatoms composed about 64% of the foregut contents. In contrast, amorphous detritus constituted about 91, 65, and 86% of the gut contents during the fall, winter, and summer, respectively. Diatom consumption was estimated to be responsible for 58% of the annual production.
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