Simulium wygodzinskyorum Coscarón & Py-Daniel was originally described based on a small number of specimens collected in Junín Province, Peru. We sampled in the same province as the type locality of this species, collecting last-instar larvae and pupae. Since the original larval description of this species was based on a single immature individual, our objective is to provide a last-instar larval description and also to provide additional morphological information on the pupa and male genitalia of this species. Some morphological characteristics not reported before for this species, such as, dorsal tubercles on larval abdominal segments, are described. Abdominal chaetotaxy of pupae is revised and the male ventral plate is fully illustrated, also it is discussed the importance of standardizing the position in which the ventral plate is illustrated. This species was collected in a stream with 2-8 m in width, exposed to sunlight with rocks of different sizes, in low density.