Xylopriona, as used here, is a quite heterogenous group gathering Monardia -like Micromyini with claw-long empodia and leaf-shaped translucent antennal sensilla ( Jaschhof & Jaschhof 2009: 208). Defined in such a vague manner, this is no doubt an artificial grouping, maintained to avoid fragmentation of Monardia -like micromyines into a plethora of monotypic or arbitrarily defined genera. The issue here is illustrated using the example of a new species, named M. ( X.) obscura, whose male morphology perfectly fits Xylopriona except that the antennal sensilla are multi-branched ( Fig. 18). This type of sensilla was previously unknown to occur in Micromyini. However, we refrain from assigning M. ( X.) obscura to a genus of its own because the merit of antennal sensilla morphology for the classification of Micromyini is a poorly understood issue. Adding to the problem, we know that the greater part of micromyine diversity is undescribed and to be found in the Eastern Palearctic, Oriental and Neotropical regions rather than in Europe (unpublished data). In other words, we have to accept that a sound generic revision of Micromyini is not achievable on the basis of European material alone. The limiting factor for tackling a revision of world Micromyini is the lack of resources for such a laborious project.
The other new Xylopriona described here is a member of the species group around M. ( X.) toxicodendri (Felt), a well circumscribed, monophyletic subset of Xylopriona (see Jaschhof & Jaschhof 2009: 212 f.). The toxicodendri group poses a twofold taxonomic problem, insofar as its relationship to other Xylopriona is obscure and the namegiving species, M. ( X.) toxicodendri, is now known to be a complex of several discrete species, not a morphologically plastic, cosmopolitan species as previously believed ( Jaschhof & Jaschhof 2009: 213). Unpublished material at our disposal suggests that there are at least eight different toxicodendri -like species present in Sweden.