Xylocopa violacea can easily be confused with Xylocopa valga.
Both species are common in West, Central and South Europe.
In eastern and southern Europe, Xylocopa valga is more common than Xylocopa violacea.

The males of both species are easy to distinguish under field conditions: in X. violacea, antenna segments 11 and 12 are orange (clearly shown on photo 1) and segment 13 (apical) is black and characteristically curved, whereas X. valga males have black straight antennae.
A stereoscopic microscope is needed to study females of both carpenter bee species.
Their antennae differ with regard to the length of the base segment (shorter in X. valga) as well as the number and distribution of sharp minute denticles on the exterior surface of hind tibia (more numerous in X. valga).

First 4 photos: A male. Reichenau Island, Baden-Württemberg, Germany, 11 August 2020
5th photo: A female. Gailingen am Hochrhein, Baden-Württemberg, Germany, 10 August 2020