Rhoptromeris strobigena is described, compared with related species, and included in a supplement to a previous key to NW European Rhoptromeris spp. Observations on its biology and courtship behaviour are reported. The parasitoid was reared from puparia of Gaurax and Hapleginella spp. (Diptera: Chloropidae) obtained from cones of Abies procera, Larix decidua, and L. kaempferi growing in the Netherlands. Specimens collected in Sweden and Italy were also examined. In contrast to most other Rhoptromeris spp., R. strobigena does not exhibit morphological features linked to reduced flight capacity. The retained good power of flight and an association with trees are considered as plesiomorphic conditions, which R. strobigena shares with most species of the closely related genera Armigerina, Nordlanderiana and Trichoplasta. A checklist of Holarctic Rhoptromeris spp., including nine valid species, presents one new generic synonym (Striatellia Belizin = Rhoptromeris Förster) and two new combinations. Another three new combinations and two new synonyms are given in a list of species excluded from Rhoptromeris, which are assigned to the genera Didyctium, Leptopilina, or Trichoplasta.