Ingestion and Growth in Sericostoma personatum (Trichoptera) in Relation to the Nitrogen Content of Ingested Leaves

Abstract

Sericostoma personatum Spence was given autumn-shed leaves with differing nitrogen content: Fagus silvatica L. 1.33 % N of ash free weight, Picea abies (L.) Karst. 1.48 % N, Quercus borealis Michx. 2.15 % N, and Alnus glutinosa (L.) Gaertn. 4.82 % N. Leaves were preferred in the sequence Alnus Quercus Fagus/Picea. Ingestion by Sericostoma was significantly lower when fed Alnus than Fagus, Picea, and Quercus. Growth was significantly greater on Alnus and Quercus than on Picea and Fagus. Gross growth efficiency (G/I), calculatedon the basis of ash free weight, was 1.53-9.38 % and was positively correlated with leaf nitrogen. Calculated on a nitrogen basis, G/I was 13-22 %. The nitrogen content of the detritus may explain the low utilization efficiencies commonly reported for detritivores.