Phthiracarus species (Acari: Oribatida: Phthiracaridae) from New Zealand, with description of a new species, redescription of Phthiracarus pellucidus and a key to 19 described species from the Australian Region Author Liu, Dong Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, P. R. China; Author Zhang, Zhi-Qiang Landcare Research, Auckland, New Zealand; & Centre for Biodiversity & Biosecurity, School of Biological Sciences, University of Auckland, Auckland, New Zealand text Journal of Natural History 2016 J. Nat. Hist. 2016-03-10 50 1463 1472 http://dx.doi.org/10.1080/00222933.2016.1145275 journal article 10.1080/00222933.2016.1145275 1464-5262 5206417 Phthiracarus pellucidus Ramsay, 1966 ( Figure 2 ) Redescription Measurements. Prodorsum: length 195–232 width 125–140, height 77–100, setae: ss 25, ro 35, in 63, le 45, ex 25; notogaster: length 335–454, width 240–335, height 235–322; setae: c 1 80, c p 90, d 1 85, e 1 80, h 1 81, ps 1 80, ad 1 50, ad 2 40, ad 3 37, an 1 12, an 2 12; genito-aggenital plate 85 × 130, ano-adanal plate 65 × 145. Integument. Colour yellowish. Entire surface of idiosoma punctate. Prodorsum ( Figure 2A–B ). Median carina and posterior furrows absent; lateral carinae very weak, nearly invisible; sigillar fields invisible; sensilli ( ss ) short with rounded head; other prodorsal setae ( in, le, ro, ex ) thin, smooth and attenuate; comparative length: in > le > ro > ex = ss , mutual distance: in – in / ro – ro ≈ 5.4. Notogaster ( Figure 2A ). Setae of notogaster ( c 1 / c 1 – d 1 ≈ 0.7) thin, smooth and attenuate; setae c 2 further away from anterior margin, setae c 3 nearest; vestigial setae f 1 not observed; one pair of lyrifissures ia present. Venter ( Figure 2A, C–D ). Setae h of mentum nearly as long as distance between them; seven pairs of genital setae ( g ) with formula: 4:3; ano-adanal plates each with five setae, comparative length: ad 1 > ad 2 > ad 3 > an 1 = an 2 . Legs ( Figure 2E–F ). Setal counts for leg segments (without tarsi): I: 1–3–2(2)–5(1); II: 1–3–2(1)–3(1), III: 2–2–1(1)–2(1), IV: 2–1–0–2(1); setae d on femora I situated in the middle of segment, at the level of setae l’’ ; setae v’ on femora I absent; setae l’ on genua IV absent; setae a’’ on tarsi I and setae ft’’ on tarsi II curved distally; setae a’’ on tarsi II curved distally; setae s and pv’ on tarsi IV present; setae s on tarsi I and II present. Material examined Three adults ( NIGA , in alcohol, 72/211), New Zealand : Middle I ., Mercury Is., CL., from litter, 21 November 1972 , leg . G .W. Ramsay. Remarks These specimens were collected by G .W . Ramsay who first described this species ( Ramsay 1966 ). Compared to the holotype , these specimens have longer notogastral setae. Figure 2. Phthiracarus pellucidus Ramsay, 1966 : (A) lateral view of body (legs removed); (B) prodorsum, dorsal view; (C) right side of ventral plate; (D) mentum of subcapitulum; (E) femur I; (F) tibia IV. Scale bars: A = 100 μm; B–F = 50 μm. Key to species of Phthiracarus known from the Australian Region 1. Dorsal and lateral regions fused on prodorsum........................................................................ ............................................................................................. P. curiosus Niedbała, 1998b (Hawaii) – Dorsal and lateral regions not fused on prodorsum........................................................... 2 2. Sensilli long and narrow, their length more than 10 times their width.................... 3 – Sensilli short and wide, their length much less than 10 times their width.............. 7 3. Interlamellar setae situated anterior to lamellar setae........................................................... .............................. P. pygmaeus Balogh, 1958 (Melanesia, Polynesia, Hawaii, Australia ) – Interlamellar setae situated between lamellar setae........................................................... 4 4. Lateral carinae on prodorsum absent, lamellar setae minute, shorter than rostral setae.............................................................................. P. tubulus ( Hammer, 1972 ) (Polynesia) – Lateral carinae on prodorsum present, lamellar setae considerably longer than rostral setae........................................................................................................................................... 5 5. Rostral setae positioned very close to each other, distance between rostral setae less than one-fifth the length between lamellar and interlamellar setae; four pairs of notogastral lyrifissures present; formula of genital setae: 6(4 + 2): 3........................ ................................................................. P. banksi Niedbała, 1987 ( New Zealand , Australia ) – Rostral setae positioned normally, distance between rostral setae more than one-third the length between lamellar and interlamellar setae; two pairs of notogastral lyrifissures ia and im present; formula of genital setae: 7(4 + 3): 2.. .............................................................................................................................. 6 6. Vestigial setae f 1 located anterior to setae h 1 , setae v’ on femora I absent................. ........................................... P. crispus Hammer, 1972 (Polynesia, Hawaii, New Caledonia ) – Vestigial setae f 1 located posterior to setae h 1 , setae v’ on femora I present............. ...................................................................................... P. fraternus Niedbała, 1998a (Polynesia) 7. Notogastral setae long and flagellate, setae c 1 longer than distance between setae c 1 and d 1 ................................................................................................................................................ 8 – Notogastral setae short and not flagellate, setae c 1 shorter than distance between setae c 1 and d 1 .. .................................................................................................................................. 9 8. Two pairs of notogastral lyrifissures present.. P. reductus Niedbała, 1998b (Hawaii) – Four pairs of notogastral lyrifissures present... P. swiftae Niedbała, 1998b (Hawaii) 9. Four or five pairs of adanal setae present................................................................................... .......................................................................... P. probus Niedbała & Colloff, 1997 ( Australia ) – Three pairs of adanal setae present........................................................................................ 10 10. Three or four pairs of notogastral lyrifissures present.. .................................................. 11 – One or two pairs of notogastral lyrifissures present........................................................ 12 11. Three pairs of notogastral lyrifissures present; prodorsal, notogastral and anoadanal setae long..................................................... P. obscurus Niedbała, 1986 ( Australia ) – Four pairs of notogastral lyrifissures present; prodorsal, notogastral and ano-adanal setae minute...................................................................... P. minutus sp. nov. ( New Zealand ) 12. One pair of notogastral lyrifissures present; seven pairs of genital setae present.... ............................................................. P. pellucidus Ramsay, 1966 ( New Zealand , Australia ) – Two pairs of notogastral lyrifissures present; nine pairs of genital setae present.. 13 13. Setae ad 1 and ad 3 arranged in one row with anal setae...................................................... ................................................................... P. anonymus Grandjean, 1933 (Hawaii, Australia ) – Setae ad 1 and ad 3 arranged not in one row with anal setae...................................... 14 14. Lateral carinae on prodorsum present ................................................................................... 15 – Lateral carinae on prodorsum absent ................................................................................... 16 15. Setae ps arranged in one row; genua IV without setae...................................................................... ................ P. paucus Niedbała, 1991 ( Papua New Guinea , Micronesia , Polynesia, Australia ) – Only setae ps 2 – ps 4 in one row, setae ps 1 situated highly at level of setae h 3 ; genua IV with one pair of setae....................... ..................... P. plenus Niedbała, 1998b (Hawaii) 16. Distal ends of heads of sensilli rounded, setae ad 1 and ad 2 on ano-adanal plate vestigial................................................................................................................................................ 17 – Distal ends of heads of sensilli pointed, setae ad 1 and ad 2 well developed.. 18 17. Setae ps 3 situated ventral to level of setae ps 2 . P. perlucidus Niedbała, 1994 (Hawaii) – Setae ps 3 situated nearly at same level of setae ps 2 ............................................................... ................................................................................................. P. insularis Jacot, 1935 (Polynesia) 18. Interlamellar setae more than twice longer than lamellar setae, setae l on tibiae IV present...................................................................... P. persimilis Niedbała, 1998a (Polynesia) – Interlamellar setae less than twice longer than lamellar setae, setae l on tibiae IV absent................................................... P. inacessus Niedbała, 1998a (Polynesia, Australia ) Note: We suspect that P. perlucidus Niedbała, 1994 is a junior synonym of P. insularis Jacot, 1935 , although we did not check the type specimens. These two species are different from each other only in the insertion of setae ps 2 and ps3, which is a feature subject to individual variation.