Movements of self‐marked caddisfly larvae, <i>Chyrnda centralis</i> (Trichoptera: Limnephilidae), in a Sierran spring stream, California, U.S.A.

Abstract

SUMMARY. 1. The tendency of larvae of Chyranda centralis to mark themselves by adding coloured plastic segments to their cases was used to study instream movements of the species. Plastic strips of different colours were placed at measured distances down a small spring stream and larvae cut pieces and incorporated them in their cases. 2. Over 50% of the marked population moved upstream into cooler water prior to pupation in an exceptionally dry year. The greatest distance moved upstream by a single larva was 56.9m, In a wet year, when daytime stream temperatures were cooler, 11–28% of the marked population moved upstream. Downstream movement occurred in both years late in the fifth instar. 3. Larvae selected yellow in preference to other colours in laboratory tests and they preferred heavy, textured plastic to light, smooth plastic as they neared pupation. 4. Upstream movements, found also in Desmana bethula (Trichoptera: Limnephilidae) in the same spring stream, may be an adaptation for avoiding pupation in areas of high temperature, low oxygen concentration, or intermittent flow.