The adults reach 15–17 mm long. They have three yellow bands on an otherwise black abdomen and thus closely resemble wasps in the form of mimicry. The first two bands are completely or partially interrupted by a black wedge. The head has feather-like antennae, and the wings have darkened patches in the middle and on the tip.
When annoyed, they even sound like wasps.
Chiswick House Gardens in July 2022