Microdistribution and colonization of Simulium vittatum (Diptera: Simuliidae) larvae on natural and artificial substrates.

I conducted a field study of natural substrates (cobbles) in two streams to examine microhabitat selection by larvae through correlations of black fly Simulium vittatum Zetterstedt (Diptera: Simuliidae) density with measured abiotic quantities. Flow variables (Froude number) best explained larval densities whereas combined substrate surface qualities (evenness, amount of periphyton) were of secondary importance. Positive correlations were found between simuliid densities and those of theory taxa, especially chironomids (Diptera), suggesting co-occurrence. Laboratory experiments examined larval black fly responses to specific substrate characteristics (evenness, texture, periphyton). At low density (2-4 larvae/cm$\sp2$), larvae avoided smooth, even substrates. At high density (10+ larvae/cm$\sp2$), there was no apparent selection, except in the presence of periphyton. A field colonization experiment demonstrated that black flies colonize new habitat (ceramic tiles) quickly (within 24 h). Numbers subsequently decline with time due to habitat degradation as periphyton and other materials accrue. (Abstract shortened by UMI.)Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1992 .B434. Source: Masters Abstracts International, Volume: 31-04, page: 1654. Thesis (M.Sc.)--University of Windsor (Canada), 1992