Roháček et al., 2016
Ch. tenebrica is a dark (blackish brown) species very similar (including chaetotaxy) to Ch. nigra. It differs from the latter in having the head with frons and gena more extensively yellowish to reddish brown, antennae yellowish brown (see Fig. 1) including 1st flagellomere which can be darkened only dorsally and apically (the latter completely black in Ch. nigra), and markedly lighter legs with all tibiae yellow (mid and hind tibiae brown in Ch. nigra). Comparison of structures of the male genitalia of a specimen from Bohemia revealed a surprising similarity to those illustrated by Shatalkin (1986). Because the majority of C. European specimens recorded above were originally misidentified as Ch. nigra by V. Martinek it is probable that also some other records of this common species may include misidentified specimens of Ch. tenebrica.
There's a picture of it in the above paper too.
Europe: Countries (published), online at Fauna Europaea, Occurrences at GBIF