Adult highly chitinous; dull purplish-brown, surface roughened and minutely specked with small greyish or colourless waxy granules. In small examples these granules are close together; in larger, well-fed specimens they become more widely separate, owing to the expansion of the intermediate tissues. Form highly convex; usually distinctly angular, with prominent median longitudinal and two transverse ridges; a smaller longitudinal raised line connects the transverse ridges on each side. Eyes inconspicuous.