Oncopsis

Identification: usually dissection of male genitalia is needed for certain identification. 

Ecology: adults and larvae on trees from the genera Betula, Alnus, Carpinus, Corylus and Ulmus.

Key (males):

1a Ventral margin of aedeagus S-shaped curved -> 2

1b Ventral margin of aedeagus convex and evenly curved -> 5

2a Appendage of pygofer with two short appendages of ± equal length -> Oncopsis subangulata

2b Appendage of pygofer with one long and one shorter appendage -> 3

3a Appendage of pygofer as follows: longer appendage with ± distinct inflection point, shorter appendage straight or slightly curved outwards. Face usually with extensive coloration, on Betula -> Oncopsis flavicollis*

3b Appendage of pygofer as follows: longer appendage ± evenly curved, shorter appendage straight or slightly curved interiorly. Face usually without extensive coloration, on Carpinus or Corylus -> 4

4a Face often with distinct coloration, median band present, on Carpinus -> Oncopsis carpini

4b Face normally without distinct coloration, median band absent, on Corylus -> Oncopsis avellanae

5a Genital style narrow, smaller species, on Betula -> 6

5b Genital style slender, smaller species. Further characters: median band on face always present, discoidal cross-band usually present, appendage of pygofer as follows: longest appendage ± straight or slightly S-curved. On Betula -> Oncopsis tristis 

5b Genital style broad, usually bigger species ->6

6a Appendages of pygofer as follows: longest appendage strongly curved exteriorly, shorter appendage weakly curved. Face without distinct coloration. On Betula -> Oncopsis appendiculata

6b Different -> 7

7a Appendages of pygofer distinctly of different length, on Alnus -> Oncopsis alni

7b Appendages of pygofer ± of equal length or not distinctly different -> 8

8a Discoidal cross-band of face present, broad and distinct. On Alnus (incana) -> Oncopsis planiscuta

8b Discoidal cross-band of face absent. On Ulmus -> Oncopsis krios

*This species might in fact be a speciesgroup, containing up to three biological species.