Lateral Dispersal of Adult Trichoptera: Flight Distance and Traveling Pattern

Trichoptera species (caddisfly) are usually used as bio-indictors for surface water quality due to their sensitivity to environmental changes, and if assessing water quality with light-trapped adults, knowing their travelling patterns will improve the accuracy of such assessments. To investigate how far a caddisfly will migrate from their emerging stream, three streams in South Carolina with different widths (Wildcat Creek 1.2 m, Brasstown Creek 11.2 m and Chattooga River 26.95 m) were selected for this study with light traps placed at three distances (0 m, 50 m, 100 m) from the streams. How long and when? Both species richness and abundance decreased as the distance from the stream increased. Interestingly, the intensity of a negative correlation between abundance and distance was gradually intensified with increasing width of a stream. At each stream, the community composition of species captured from the greatest distance was the same as at 0 m, indicating that within 100 m horizontal distance, caddisfly individuals are more likely to be emerging from the nearby stream than from water far away from the studied stream.