Stylocephalus occidentalis n. sp. (Apicomplexa: Eugregarinida) is described from Trimytis pruinosa (Coleoptera: Tenebrionidae) collected from Keith County in the Sandhills of western Nebraska. Measurements are means in micrometers. Developing trophozoites solitary; epimerite a complex of terminal epimerite and intercalating diamerite; epimerite shallowly ovoid to transversely elliptoid, with transverse basal constriction at junction with diamerite, length 0.5–1 times width, approximately 3–4 times that of diamerite; width approximately equal to that of diamerite; diamerite roughly cylindrical to spindle-shaped, without significant anterior taper, little or no evidence of longitudinal folds, length approximately twice width. Association late, frontal, isogamontic. Gamont protomerite depressed ovoid to very broadly ovoid, length 27.3, width 35.1, anterior distance to widest point 15.4. Protomerite–deutomerite septum clearly marked and constricted, width 34.6. Deutomerite often with distinct marginal crenulation, narrowly obovoid to very narrowly obovoid, length 356.5, maximum width 57.6, anterior distance to widest point 26.3, equatorial width 35.1, ±12.5, 29. Total length 381.5. Nucleus ellipsoid, length 32.5, width 18.8; with 0 or 2 polysomal endosomes. Gametocysts roughly spherical; diameter 205.0; wall desiccating to become paper-like, slightly papillated, dehiscing by simple rupture, releasing oocysts in coiled chains, epispore packet absent, gametocyst residuum present. Oocysts dark brown to black, axially asymmetric, broadly deltoid, gibbous in lateral aspect, slightly keeled in dorsal aspect; length 9.8, height 7.9; with slight terminal protuberances and 2 central, spherical residua.