Adults measure approximately 4 cm (1.5 inches), are black with six relatively large, white, dorsal spots (four over the elytra and two on the thorax).
Its primary color is black, but it has two bright-red eyespots on its thorax, as well as yellow edging on its thorax and wing case.
A number of endemic darkling beetles species- such as the Namib Desert beetle- have bumpy elytrons with a pattern of hydrophilic bumps and hydrophobic troughs.
Its name is commonly believed to be derived from the rounded bonnet that resembled the elytra (wing covers) of a Scarab beetle, but the name really comes from a more conventional source, Scammell's idea of the combination of an Arab horse (which the Mechanical Horse replaced in BR usage) and the word Scammell.