Velocity Effects on the Spatial Patterning and Density of a Caddisfly in the Chippewa River

Abstract

Larvae of the caddisfly Leucotrichia live in silk cases attached to hard surfaces in streams. They construct cases in summer, overwinter as larvae, and emerge as adults the following June or July. Leucotrichia larvae are very territorial. Territory size is determined by the availability of benthic algae, which serves as food for the larvae. Larvae spend about half their time reaching out of their case to graze on the algae surrounding their case. In this study I examined the relationship between near-bed current velocity and the spatial patterning of Leucotrichia on the Chippewa River streambed. I measured larval case density, the spacing between cases, and the angle of case orientation relative to flow.