Semiotus imperialis can reach a length of . Basic colour of the body varies from fulvus to luteus. The head shows two small black spot, respectively in the middle of the anterior and the posterior border. Pronotum has a reddish median longitudinal stripe and two black marginal maculae in addition to two irregular longitudinal streaks. The elytra have a glabrous surface with fine interstrial punctures and two spines on each apex.
