Abstract
A new simuliid species, Simulium (Simulium) visuti sp. nov., is described on the basis of the females, males, pupae and mature larvae collected from northern Thailand. This new species is assigned to the griseifrons species-group of the subgenus Simulium (Simulium), and is characterized by the haired basal portion of the radial vein of the wings not only in the female but also in the male adults. Morphological characteristics differing from those of four related known species are noted.
