Length, 18 to 20 millimetres. [58] Black, with bristling whitish hairs on the head, the thorax and the base of the first segment of the abdomen. Long upper lip, yellow. Ridge-shaped shield, forming a sort of trihedral angle, of which one side, that of the fore-edge, is all yellow, while each of the two others is marked with a large rectangular black patch, touching the adjacent one, so that the two together form a chevron; these two patches and also the cheeks are covered with a fine silvery down. Cheeks and a median line between the antennæ, yellow. The back rim of the eyes has a long yellow border. Yellow mandibles, brown at the tips. First two joints of the antennæ, yellow underneath, black above; the others, yellow. Prothorax, black, with its sides and dorsal division yellow. Mesothorax, black; the callous dot and a small dot on either side, above the base of the intermediate legs, yellow. Metathorax, black, with two yellow spots behind and a larger one, on either side, above the base of the hind-legs. The first two spots are sometimes missing. Abdomen, brilliant black above and bare, except at the base of the first segment, which bristles with whitish hairs. All the segments have a wavy transversal band, wider at the sides than in the middle and nearer to the hinder edge as the segment is farther back. On the fifth segment the yellow band touches the hinder edge. Anal segment, yellow, black at the root, covered all over the dorsal surface with rusty-red papillæ, forming a base for bristles. A row of similar bristle-bearing protuberances occupies also the hinder edge of the fifth segment. Underneath, the abdomen is brilliant black, with a triangular yellow patch on either side of the four intermediary segments. Black hips; thighs, yellow in front, black behind; yellow legs and tarsi. Transparent wings. In the male the chevron mark on the shield is narrower, or even entirely absent, in which case the face is all yellow. The bands on the abdomen are a very pale yellow, almost white. The sixth segment has a band like those which come before, but shorter and often reduced to two dots. The second segment has underneath it a longitudinal carina, raised and spine-shaped at the back. Lastly, the anal segment carries below it a rather thick angular projection. The rest is the same as in the female.