Stenocephus janseni sp. nov., a new species of stem-sawfly from Germany (Hymenoptera: Cephidae)

Stenocephus janseni sp. nov. (Hymenoptera: Cephidae) is described from Brandenburg, eastern Germany, known only from the female holotype. It possesses an unusual combination of “generic” morphological characters, which makes its placement in Stenocephus Shinohara, 1999 provisional. Compared to other Stenocephus species, differences in the morphology of the lancet are particularly striking. Genetic data for S. janseni sp. nov. place it unequivocally in the Hartigiini, but rather distantly from other genera of this tribe which have so far been sequenced. The three previously described Stenocephus species are recorded from the East Palaearctic. No genetic data are currently available for these. Pachycephus nigratus Dovnar-Zapolskij, 1931, comb. restit., is no longer treated as belonging to Phylloecus Newman, 1838, but as a member of the genus in which it was originally described.