Anatomical features of male and female Scolytus opacus Blackman, infesting Abies lasiocarpa (Hook.), and Scolytus abietis Blackman (Coleoptera: Curculionidae: Scolytinae), infesting Abies grandis (Douglas) and Abies concolor (Gord. & Glend.), were compared by light and scanning electron microscopy. Diagnostic features involve body size; striations on the underside of the head, which have a stridulatory function; shape of the submentum; and several characters on abdominal sternites 1 and 2. Because of differences in these features of the two taxa, and because the two populations infest different tree species and are sympatric in Idaho, we reinstate S. abietis as a valid species.