Hydrachna bulgarensis K. Viets, 1940, nov. stat. Hydrachna perpera bulgarensis K. Viets, 1940 Material examined: Holotype male, SMF 5917, Bulgarien, See im Rila­Gebirge, 2200 m, Valkanov coll. Discussion: The author placed this taxon as a subspecies of the little known H. perpera which is here synonymized with H. processifera. Hydrachna bulgarensis obviously belongs to the geographica species group (Cx­4 with four setae, mediocaudal angles extended and narrow; gnathosoma with very long rostrum; palp slender, P­2 ventrally strongly concave, with 20 fine and short dorsal setae). Further characteristics are: P­3 proximally concave, most of the segment straight, with dorsal and ventral margins slightly converging distally, bearing five dorsal and six lateral setae; P­4 short, dorsal and ventral margins straight. In contrast to the figure of Viets (1940, Fig. 3), the genital setae are differentiated into two groups, with the setae flanking the gonopore a little longer and more densely arranged than on the remaining plate surface. In the form of the male gonopore with equally rounded anterior margin and the curved shape of the frontal sclerites, H. bulgarensis is most similar to H. incisa. Minor differences are found in the genital field not being indented anteriorly, the presence of an elevated median ridge between the acetabula­bearing areas and generally taller palp segments (L/H P­2 590/310, 1.90; P­3 570/190, 3.00; P­4 235/110, 2.14). For a better understanding of this taxon, possibly a junior synonym of H. incisa, a study of the variability of the latter taxon is necessary.

Published as part of Davids, Kees, Sabatino, Antonio Di, Gerecke, Reinhard, Gledhill, Terence & Smit, Harry, 2005, On the taxonomy of water mites (Acari: Hydrachnidia) described from the Palaearctic, part 1: Hydrachnidae, Limnocharidae and Eylaidae, pp. 36-64 in Zootaxa 1061 on page 39, DOI: 10.5281/zenodo.170186