EFFECTS OF AUFWUCHS ON COLONIZATION BY SIMULIIDS (SIMULIIDAE, DIPTERA)

While different studies investigated effects of surface properties on the adhesion and population dynamics of marine sessile organisms (Bala nidae, Bryozoa etc.), little is known about sedentary freshwater macro invertebrates. Artificial substrates were used to investigate the effe cts of Aufwuchs on density and distribution of colonizing blackfly lar vae and pupae. Although, settlement of blackfly larvae often is said t o be impeded by Aufwuchs or siltation, they colonized both bare substr ates and those on which a thick Aufwuchs cover had developed. Often no differences in density appeared on substrates exposed for less than 6 -9 d. Thus Aufwuchs apparently does not prevent initial settling of la rvae. However, simuliid densities on Aufwuchs covered substrates decli ned after several more days of exposure, suggesting that surface prope rties may affect long-term settlement.