Lasioglossum (Dialictus) aeneidorsum (Alfken, 1921) stat. rev.

Lasioglossum aeneidorsum (Alfken, 1921) has been described as a closely related species to L. nitidulum (Fabricius, 1804) . The types originate from modern day Lithuania and north-eastern Poland. Later, the taxon was also mentioned and described in detail by Lehmann (1964) from East Germany. Subsequently, this taxon was no longer used as a valid species, also because Ebmer (1976) listed it as a subspecies of L. nitidulum, and after this work it did not appear in following checklists or keys.

A detailed examination of new material of L. aeneidorsum from East Germany and L. nitidulum has now led to the result that the two taxa can be clearly distinguished and must therefore be treated as a valid species, also due to their different distribution areas. A status of subspecies as suggested by Ebmer (1988a) does not match the current status of this taxon. The third species from this complex is L. smeathmanellum (Kirby, 1802), which, however, only occurs in the extreme west of Germany and West Europe (Atlantic distribution), and is accepted as a valid species.

Females of Lasioglossum aeneidorsum can be recognised by the densely sculptured and punctate episcrobal area on mesopleuron. Interspaces are always smaller than punctures, apart from the rear lower area, and the interspaces microsculptured. It is mostly shiny and smooth with a few punctures in L. nitidulum and L. smeathmanellum . The punctation is dense on the mesoscutum, with most interspaces smaller than the diameter of the punctures in L. aeneidorsum . It is much sparser with wider interspaces in the medial and apical parts of the mesoscutum, larger than the punctures, in the two comparison species. The head is on average narrower in L. aeneidorsum, and the striation of the propodeal dorsum always reaches the end of the propodeal dorsum, whereas it ends shortly before the apex in the other species. However, both last characters seem to be variable and require confirmation with morphometric analysis. The difference in the sculpture of the episcrobal area is in the male the same as described in the female. Other characters are more variable in males than in females. For these reasons we consider L. aeneidorsum as a valid species.

Lasioglossum aeneidorsum has an eastern distribution and is found from eastern Germany to the Ural mountains in Russia, southwards to the northern Balkans, and in some places in eastern Austria (Ebmer 1988a). In Germany it is restricted to east of the river Elbe.