Case Features of Caddisfly Larvae (Sericostoma selysi) as Related to Water Velocity and Potential to Drift

ABSTRACT

Variation in case characteristics of larvae of Sericostoma selysi (Pictet 1865) as related to water velocity and resistance to passive entry into the drift was investigated in the field. Larvae from river sections of different current velocity (low: 0.30–0.35 m·s⁻¹ and high: 0.60–0.65 m·s⁻¹) were collected. Case and larval dry weight were weighed; frontal and lateral surface areas of the cases were also measured. Larvae from high-speed waters had heavier and narrower cases than those from the low-speed waters. We believe that this is an adaptation in response to water velocity, which enables larvae living under conditions of high velocity to resist the drag forces of moving water.