Wings and body with a distinct clayish hue, not pure whitish grey as in Sphinx chersis mexicanus. Mesothoracic tegula without black mesial line. Mesonotum always grey with narrow black lines, not largely brown. Abdomen with only 3 prominent transverse bands, not 4 or more as in Sphinx chersis mexicanus or Sphinx perelegans. Foretarsus 1st segment outer side and foretibia apex with elongate spines. Pulvillus reduced, without long lobe. Midtarsus 1st segment with comb, but the bristles stout but not long. Hindtibia with long apical spur half the length of 1st hidtarsal segment. Hindtarsus with 1st segment as long as hindtibia. Forewing fringe nearly all brown, the white spots covered by brown scales. Hindwing upperside with submarginal pale band much less sinuate than in Sphinx chersis mexicanus; the dark band proximal to it narrower.
Male genitalia: Uncus elongate-triangular, sulcate dorsally except at apex, which is convex, acute and downcurved; underside concave. Gnathos with a broad, rather long lobe that narrows somewhat apically and is weakly sinuate. Valve sole-shaped. Harpe divided by a broad distal sinus into a broad concave ventral lobe, the dorsal margin irregularly notched, and a long, cylindrical, horizontal process that tapers distally and curves slightly dorsad, reaching the apical quarter of the valve. Phallus produced into a long, tapering, pointed, somewhat twisted and curved process.
Female genitalia: Ostial plate with a wide apical cavity that is smooth-bottomed, without a tubercle, the plate not divided mesially as in Sphinx perelegans, Sphinx kalmiae and Sphinx leucophaeata, but the slit is indicated by some longitudinal wrinkles.