Competition between two stream dwelling filter-feeders, Hydropsyche oslari and Simulium virgatum.

This study investigated whether interspecific competition affected the abundance and distribution of Hydropsyche oslari and Simulium virgatum. In addition, I studied the mechanisms of competition between the two taxa. H.

The effect of physical disturbance on the relative abundances of two filter-feeding insects in a small stream.

We examined the importance of disturbance in determining the relative abundances of two lotic filter-feeders, Simulium virgatum and Hydropsyche oslari, in a small, coastal stream in southern California, USA.In most years, winter spates effectively scour substrata in fast-flowing areas, thereby drastically reducing stream insect populations. Newly-opened space in these areas is quickly colonized by simuliids.