Genus Pionopsis Piersig, 1894 Pionopsis (in part): Cook, 1974a, pp. 283, 284, figs. 1183–1185. Pionopsis: Smith, 1976, pp. 46–47, 83–85, 90, 92. Tiphys (in part): Wainstein, 1980, pp. 194–195, figs. 654–660. Pionopsis: Smith & Cook, 1991, pp. 554, 579. Pionopsis: Smith et al., 2001, pp. 582, 615, fig. 334. Pionopsis: Smith et al., 2010, pp. 524, 556, fig. 15.335. Diagnosis. Larva: (modified from Wainstein 1980). Character states of the subfamily Tiphyinae. Third coxal plate with transverse muscle attachment scar present. Excretory pore plate nearly circular with setae ps1 well anterior to setae ps2; excretory pore sessile. Adults (modified from Smith 1976): Character states of subfamily Tiphyinae. Fourth coxal plates with large, anteriorly concave projections covering insertions of fourth legs. Pedipalp with segments relatively long and slender and with tibia bearing a long, blade-like seta distomedially on a moderately prominent projection. Genital field bearing three pairs of acetabula. Males with genital acetabula relatively close together and borne on triangular acetabular plates that are fused posterior to gonopore but separate anterior to gonopore, and do not extend laterally beyond posteromedial angles of fourth coxal plates; second leg with tibia lacking two spatulate setae distoventrally; fourth leg with genu slightly expanded and bearing three thick swimming setae distoposteriorly, tibia slightly expanded and bearing a row of closely-spaced thickened setae posteriorly and a bulbous seta distoposteriorly. Females with genital acetabula relatively widely separated from one another and borne on triangular acetabular plates, and with second and third acetabula on each side not forming a row near posterior edge of plate that is nearly at right angles to long axis of idiosoma. Type species. Hydrachna lutescens Hermann. Species included. Pionopsis lutescens (Hermann) (Europe), P. fragilis Habeeb (North America), P. japonensis Imamura (Japan), P. latilamellis Marshall (western North America), P. paludis Habeeb (eastern North America). Distribution. Holarctic (Eurasia, North America). Discussion. Cook (1974a) treated Pionopsis as a genus that included Neotiphys as a subgenus. Smith (1976) considered Pionopsis and Neotiphys to be separate genera and this treatment was followed by Smith & Cook (1991), Smith et al. (2001, 2010), and by us here.

Published as part of Smith, Ian M., Cook, David R. & Gerecke, Reinhard, 2015, Revision of the status of some genus-level water mite taxa in the families Pionidae Thor, 1900, Aturidae Thor, 1900, and Nudomideopsidae Smith, 1990 (Acari: Hydrachnidiae), pp. 111-156 in Zootaxa 3919 (1) on pages 126-127, DOI: 10.11646/zootaxa.3919.1.6, http://zenodo.org/record/244587