(Fig. 1 B)
Diagnosis. Male genitalia of Aprionus gustavssoni are characterized by presence of flattened, spineless gonostyli (↓) in combination with 4–5 pairs of non-overlapping tegmen fingers. Furthermore, the outer surface of gonostylus is markedly concave and the tegmen is blunt-ended (↓).
This species cannot be placed in any of the species groups recognized within the genus Aprionus (see Jaschhof 1998, Jaschhof & Jaschhof 2009). There are other Aprionus incertae sedis with male genitalia superficially similar to A. gustavssoni, in particular A. laricis Mamaev & Jaschhof (Jaschhof 1998: fig. 181), A. pyxidiifer Mamaev (Jaschhof & Jaschhof 2009: fig. 103), and A. svecicus Jaschhof (Jaschhof 1998: fig. 187). To separate these species from one another, genital structures should be studied and compared in detail.
Other male characters. Body size 1.2 mm. Head. Eye bridge 4–5 ommatidia long. Postocular bristles 12, in 1 dense row. Neck of fourth flagellomere shorter than node; node with 1 complete and 5 incomplete crenulate whorls of sensory hairs, 4–6 thick hair-shaped translucent sensilla distally. Maxillary palpus 4 -segmented; first segment with hair-shaped translucent sensilla; apical segment longest. Wing. Apical portion of R 1 2.5–3 times as long as Rs. Legs. Claws thick, rectangular, with 3–4 tiny teeth. Terminalia (Fig. 1 B). Ninth tergite subrectangular, with concave, slightly reinforced anterior margin. Gonocoxa lengthened ventroapically into subtriangular lobe. Gonostylus with dense, short microtrichia apically, 2 bristles dorsosubapically. Tegmen with dark longitudinal folds apically. Subanal plate subrectangular, generally weakly sclerotized, with dark markings on posterior and anterior margins.
Etymology. This species is named after Erik Gustavsson, Skogsby, Öland.
Types. Holotype. Male (CEC 77), Sweden, Uppland, Uppsala, Fiby Nature Reserve, old-growth mixed taiga, 29 July 2009, sweepnet, M. & C. Jaschhof (in NHRS). Paratype. Male (CEC 78), same data as the holotype.