New records of water mites from Southeast Asia (Acari: Hydrachnidia) with the description of two new genera and 12 new species Pešic, V. Smit, H. Acarologia 2016 2016-07-22 56 3 393 433 625NH 322638 Thor, 1900 Thor 1900 [1053,1292,1245,1269] Arachnida Pionidae Animalia Trombidiformes 17 409 Arthropoda family  Diagnosis — Female (Male unknown): Character states of family Pionidae(see Cook 1974). Dorsum soft. All coxal setae slender, not spatulate; medial margin of Cx-III almost as long as medial margin of Cx-IV, posterior margin of Cx-IV concave, without angular projections. Genital bay very shallow, gonopore very long, genital plates broad and rounded, much smaller than gonopore, with 5 pairs of acetabula. P-3 with a very long lateral seta, P-4 with a peg-like mediodistal seta, ventral setae not associated with tubercles ( Figures 11B-C); gnathosoma with posterior anchoral process. Legs slender, swimming setae present.  Typespecies —  Schwoerbelia pioniformis  n. sp. Etymology — The genus name is in honour of Jürgen Schwoerbel (1930-2002), who described one of the pionid subfamilies. Moreover, he was one of Peši´c V. and Smit H.  FIGURE 10:  Unionicola( Majumderatax)sp., deutonymph, Mekong River, Vietnam: A – idiosoma, ventral view; B-C – palp; D – I-L-5 and -6. Scale bars – 100 µm. the editors of a new standard work on European water mites, published in the series "Süsswasserfauna von Mitteleuropa". Remarks — Due to the following characters: medial margin of posterior coxal plates formed jointly by Cx-III and Cx-IV, all setae on Cx-II and -III fine, not thickened, gnathosoma ventral margin posteriorly projecting in an anchoral process (in ventral view bifurcate as in Figure 11D), and P-4 with a distoventral peg-like seta, the female of new species resembles to those of genus  Piona. However the single female from a stream in Vietnamis unique in P- 3 with a very long lateral seta, exceeding the tip of P-5. In all known members of subfamily Pioninae Thorlateral setae on P-3 are short. The new genus resembles Huitfeldtiinae(P-3 with a very long lateral seta) which in addition to  HuitfeldtiaThor, 1900 (Holarctic), includes  LarriHarvey, 1996 ( Australia)and  GereckeaSmith & Cook, 2009 ( Canada). The new genus differs in slender, not spatulate coxal setae (present in  Huitfeldtia), posterior margin concave, without acute-angled apodemes, and a small peg, not a prominent spine-like mediodistal seta on P-4 (see Smith et al.2015). In most pionid groups, characters (sexual dimorphism on leg segments) important for classification are restricted to males. However the unique features of female from Vietnamare large enough to warrant the erection of the new genus.