Female(Fig. 7a, b, c), (to date only females have been reared from the inventory efforts) head: Frontal vitta light to dark brown, apically twice as wide as ocellar triangle, face 3 times as wide as frontal vitta; frontal bristles arise no lower than level of pedicel; lacking yellow hairs lining the margin of the frontal vitta; antenna bearing a black first flagellomere on an orange pedicel; arista black and plumose, sparsely haired with widely interspersed trichia at least 2 times as long as width of base of arista, tapering at apex of arista; proclinate orbital bristles present; parafrontal entirely silver, sparse minute hairs over upper half of fronto-orbital plate; parafacial silver; palpi orange with black bulbous tips; lacking any supravibrissal hairs. Thorax: dull grey when viewed dorsally, longitudinal vittae smudging together presuturally appearing as two black smudges separated by grey, then into a large precircular dark smudge post suturally. Vittae are nor readily discernible as bands; scutellum dark over more than 2/3 of its surface becoming grey apically concolorous with rest of thorax; anterior pair of legs yellow from coxae to tibiae, anterior femur bearing silvery pruinosity on yellow ground color, 2^nd and 3^rd pair of legs yellow from coxae to ½ of femur, with black from tibiae to tarsi. Wings: pale smoky greyish in color, vein R₄₊₅ setose beyond crossvein r-m, but ending approximately 1/3 of vein length away from wing margin; R₁ haired along its entirety. Abdomen: abdominal tergites dark shiny black medially, with bright grey band covering 1/3^rd or more of tergal surface arising at the anterior margins of abdominal tergites T4 and T5, these bands wrapping around to the underside. T3 does not bear these grey bands of pruinosity but there is a conspicuous lack of pruinosity and bristles along the anterior margin of T3. Bright yellow blotches appear along tergites T1+2, T3 and the anterior margin of T4; T3, T4 and T5 possessing medial marginal bristles, ovipositor concealed within segment 5. Lateral marginal bristles on T1+2. Lacking any discernible small yellow hairs over entire body, not as hirsute as other species, in particular lacking along anepimeron, and from underside of T1+2.

Similar to S. setipennis in the thoracic markings, however S. juanvialesi is strongly different in the coloration of the antenna, and the extent of the yellow on the legs.

This species is named in honor of Sr. Juan Viales (RIP), whose Finca San Cristobal became a large part of Sector San Cristobal of the newly forming Area de Conservación Guanacaste in the eary 1990's.

Costa Rica, ACG, Prov. Guanacaste, rain forest, 440–580 m elevation.

Reared twice from grass-eating rain forest Hesperiinae (Hesperiidae).