Hierarchical dynamics influence the distribution of immature black flies (Diptera: Simuliidae)

Adult black flies (Simuliidae) are medically important insects and they are the sole vector of Onchocerca volvulus. Immature black flies are major components of aquatic macroinvertebrate assemblages in streams and play a vital role in nutrient dynamics. In this study, we examined effect of hierarchical dynamics (spatio-temporal pattern) on the distribution of immature black flies in South Indian streams. The sampling was done in streams of Western Ghats, South India. A total of 16 species belong to two subgenera: Simulium (10 species) and Gowmphostilbia (6 species) of Simulium were observed. Alpha diversity indices were analyzed, which indicate the abundance and species richness between sampling sites. Non-parametric analysis recognized the key environmental variables including latitude and stream order. Subsequently, the monsoon influences the larval assemblages and its association was high in leaf litter as revealed through statistical analyses. Although the members of the immature black fly assemblage with different environmental factors, they are very closely related to spatial and temporal organization and secondarily with other factors prevailing in streams.