Axonopsis

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), Zootaxa 3919 (1), pp. 111-156 : 137-138

Axonopsis -like mites (sensu Cook, 1974)

Axonopsis -like mites Cook, 1974a, pp. 301–302, 330–337, figs. 1377–1379, 1381–1426.

Diagnosis. Larva (modified from Smith 1984 and based on larvae of Brachypodopsis setoniensis Habeeb , only species in group with known larvae): Character states of subfamily Axonopsinae. Third coxal plate with medial coxal apodeme absent and transverse muscle attachment scar present. Posterior edge of third coxal plate bearing prominent pointed projection. Excretory pore plate roughly elliptical in shape, bearing setae ps1, ps2, and h2 posterolaterally, with ps2 displaced medially. Numbers of setae on leg segments as follows: ITi 8 (seta Ti10 absent); ITa 11 (setae Ta8 and Ta14 absent); IITa 11 (setae Ta8 and Ta14 absent); IIITa 10 (seta Ta14 absent).

Adults (modified from Cook, 1974a): Character states of subfamily Axonopsinae. Idiosoma with dorsal shield entire and either separate from or fused with ventral shield anteriorly. Ventral shield on each side bearing a ridge that originates at lateral end of suture line between third and fourth coxal plates and extends anterolaterally. Coxal plates with all setae slender; fourth coxal plate lacking a condyle or projection associated with opening for insertion of fourth leg. Genital field bearing three or four (rarely two) pairs of acetabula on acetabular plates that are fused with ventral shield in both sexes, with suture lines well delineated or obliterated. Gnathosomal setae small. Pedipalp tibia with or without a ventral projection. Legs of males with segments unmodified or variously modified.

Genera included. Axonopsis Piersig, 1893 , Brachypodopsis Piersig, 1903 (stat. nov.), Cubanaxonopsis Orghidan & Gruia, 1981 (stat. nov.), Erebaxonopsis Motaş & Tanasachi, 1947 , Haloaxonopsis Pešić, Smit & Saboori, 2012, Hexaxonopsis Viets, 1926 (stat. nov.), Omanaxonopsis Smit & Pešić, 2010, Paraxonopsis Motaş & Tanasachi, 1947 (stat. nov.), Stokaxonopsis Cook, 1967 , Uenaxonopsis Imamura, 1961 , Vicinaxonopsis Cook, 1974 (stat. nov.). There is an undescribed species of Axonopsis -like mite from southern North America with some similarities to described species of both Axonopsis and Stokaxonopsis in the Canadian National Collection of Insects and Arachnids.

Distribution. Holarctic (Eurasia, North America), Caribbean, Arabian Peninsula, East Africa

Proposed Changes. Elevation of Brachypodopsis Piersig, 1903 , Cubanaxonopsis Orghidan & Gruia, 1981, Hexaxonopsis Viets, 1926 , Paraxonopsis Motaş & Tanasachi, 1947 , and Vicinaxonopsis Cook, 1974 from subgenera of Axonopsis Piersig, 1893 to full generic status, and transfer of subgenera Kalobrachypoda Viets, 1929 and Navinaxonopsis Cook, 1967 from genus Axonopsis to genus Brachypodopsis and subgenus Plesiobrachypoda Viets, 1942 from genus Axonopsis to genus Hexaxonopsis .

Discussion. Cook (1974a) characterized the Axonopsis -like mites as a distinct group of Axonopsinae, including the genera Axonopsis , Uenaxonopsis , Erebaxonopsis , and Stokaxonopsis . He treated Brachypodopsis , Hexaxonopsis , Kalobrachypoda , Navinaxonopsis , Paraxonopsis , Plesiobrachypoda , and Vicinaxonopsis as subgenera of Axonopsis , but noted that several of them were distinctive enough to be considered for full generic ranking. Orghidan and Gruia (1981) subsequently proposed Cubanaxonopsis as a subgenus of Axonopsis . Here we propose to retain the four genera recognized by Cook, elevate five of the former subgenera of Axonopsis to full generic rank, and transfer the three remaining former subgenera of Axonopsis to other genera to reflect their phylogenetic affinities.