New synonymy to Simulium (Inaequalium) diversibranchium Lutz, with comments on the Inaequale species-group (Diptera, Simuliidae)

Simulium (Inaequalium) Coscaron and Wygodzinsky, 1984 is a homogeneous subgenus widely spread on the Neotropical Region, which the adults can only be reliably identified from linked-reared specimens. Despite many revisionary works only a single character of the pupal gill separates Simulium diversibranchium Lutz, 1910 from S. mariavulcanoae Coscaron and Wygodzinsky, 1984. Specimens of both species show that S. mariavulcanoae is a junior synonym of S. diversibranchium. The relationship between S. diversibranchium and S. subnigrum Lutz, 1910 needs further investigation. Some features of the pupal gill often used as diagnosis in Simulium (Inaequalium) species, such as the direction of gill filaments or the height of the bifurcation of the secondary or tertiary branches of the pupal gill are highly polymorphic, making its use as diagnostic character not reliable.