Aprionus Kieffer, 1894

Jaschhof, Mathias & Jaschhof, Catrin, 2020, An update of Micromyinae (Diptera: Cecidomyiidae) taxonomy, with descriptions of a new genus and 13 new species from Northern Europe, Zootaxa 4750 (3), pp. 349-369 : 352-353

Aprionus Kieffer, 1894

= Azygotricha Plakidas, 2017 syn. nov.

= Ampullomyia Plakidas, 2018 syn. nov.

The genus Aprionus is, after Peromyia , second within the Micromyinae in terms of species richness. Only eight of previously 133 valid species are non-Palearctic ( Jaschhof & Jaschhof 2017b; Plakidas 2017b, 2018). However, vast stretches of the Palearctic region are entirely unexplored for this genus, while a comparatively small, integral part of it – the land area of Sweden – has been shown to contain 95 different species (Jaschhof & Jaschhof 2017). This imbalance suggests that the number of undiscovered Aprionus should be immense; and, indeed, unnamed Aprionus we have seen over the years from only a few places in the Palearctic outnumber all the species previously named in the genus (unpublished data). Most descriptions of Aprionus published in the past 60 years were based on the morphology of male adults, the consequence being that we are comparatively uninformed regarding female and larval structures. Both the generic definition and intrageneric classification of Aprionus are largely based on male characters ( Jaschhof & Jaschhof 2009: 219 ff.). According to present opinion, the male genitalia are the only morphological structures of Aprionus diverse enough to provide taxonomists with sufficient information. Unawareness of this enormous diversity has repeatedly misled taxonomic authors to separate single, seemingly aberrant species from the core of the genus, or Aprionus sensu stricto, and classify those in discrete subgenera (see the synonymy of Aprionus in Gagné & Jaschhof (2017)) .

Recently, two new genera were proposed to absorb two newly described species that according to our definition are representatives typical of the Aprionus smirnovi Mamaev group ( Jaschhof & Jaschhof 2009: 263 ff.): Azygotricha rotundata Plakidas, 2017 and Ampullomyia surcula Plakidas, 2018. As regards generic characters of Azygotricha, Plakidas (2017b) referred to the lack of tegminal processes (which is the key feature of the smirnovi group), along with female and larval traits, which in our opinion are uninformative here because the respective conditions in most Aprionus , including the smirnovi group, are unknown and thus inaccessible to comparison. Ampullomyia, described on the basis of male traits, differs from Aprionus in the absence of the subanal plate ( Plakidas 2018), which in our opinion is a less than convincing argument as long as all other characters speak for Aprionus . We know of several Aprionus , both within and outside the smirnovi group, where the subanal plate is hard to discern due to its largely membranous texture ― even less so when, for lack of experience, one does not know what exactly to look for as to determine the plate’s presence. Moreover, Ampullomyia surcula as described by Plakidas (2018) is indistinguishable from Aprionus umbrellus Mamaev & Berest from Ukraine. The present senior author studied the holotype of A. umbrellus a few years ago; in addition we know of a conspecific male from Germany (unpublished). The Ger- man specimen, which we reexamined here, has a soft, sparsely microtrichose structure in the position where other Aprionus hold the subanal plate. Apparently, A. umbrellus is one of those Aprionus whose hypoproct is retained in the plesiomorphous state. In conclusion, the type species of Azygotricha and Ampullomorpha come within the limits of the genus Aprionus as presently defined, which is why we treat both names as junior synonyms.

Among our Swedish material of Aprionus are eight unnamed Aprionus , of which two are qualified for taxonomic description here. Both are members of the A. spiniger (Kieffer) group ( Jaschhof & Jaschhof 2009: 275).