The body of the Canthophorus dubius shieldbug is oval, black or dark blue, sometimes metallic green or bright violet, and can reach a length of 6–8 millimeters (0.24–0.31 inch) and a width of 3.5–4.5 millimeters (0.14–0.18 inch).
The body of the Canthophorus dubius shieldbug is oval, black or dark blue, sometimes metallic green or bright violet, and can reach a length of 6–8 millimeters (0.24–0.31 inch) and a width of 3.5–4.5 millimeters (0.14–0.18 inch).