Review of the Dichotrachelus alpestris Stierlin, 1878 species group with evidence for a species complex group with evidence for a species complex of D. augusti F. Solari, 1946, and D. sondereggeri sp. nov. from Switzerland (Coleoptera, Curculionidae)

The three species belonging to the Dichotrachelus alpestris species group are reviewed. Thereby the lectotype of D. walteri BARAJON, 1947 is designated, and its name is proposed as syn. nov. of D. alpestris STIERLIN, 1878. Three deviating forms of the aedeagus of D. augusti F. SOLARI, 1946 are presented, which indicate a species complex. More specimens of this rarely collected species are needed to clarify this circumstance. D. sondereggeri sp. nov. from Valposchiavo in the Swiss canton of Grisons represents the easternmost finding of the species group. The new species is described and illustrated, and details on its biology are reported. An overview of the distribution, and a key to all species of the group are provided.