Lateral Dispersal of Adult Aquatic Insects (Plecoptera, Trichoptera) following Emergence from Headwater Streams in Forested Appalachian Catchments

We monitored the lateral dispersal of adult Plecoptera and Trichoptera following emergence from 4 headwater streams that drain adjoining forested catchments on the Allegheny Plateau of West Virginia. We assessed these dispersal distances to examine the lateral distance traveled by particular taxa and the variation in these distances among streams. The number of adults captured decreased with distance from a stream for 16 of the 17 more common plecopteran and trichopteran taxa. The 16 taxa had mean maximal lateral dispersal distances of from 44.1 m for Homoplectra monticola (Flint) to 81.4 m for Leuctra spp. These distances are generally <1/2 the median distance of 301 m between adjacent headwater streams in this region. This suggests that direct lateral dispersal of adults among headwater streams may be relatively uncommon for many species.