Review of the mite subfamily Arctoseiinae Evans with a key to its genera and description of a new genus and species from Siberia (Parasitiformes, Mesostigmata, Ascidae).

We redefine the subfamily Arctoseiinae of the family Ascidae, and describe a new genus, Maxiniagen. n., based on a new species, Maxinia arctomontanasp. n., whose adults display a combination of attri-butes uniquely different from other genera of the subfamily. The geographical range of Maxinia arctomontana is limited by arctic and mountain landscapes of Siberia. This description provides furtherdata on the arctic distribution and morphological diversity of the subfamily Arctoseiinae, which is unusually well represented in that region (26-83% in local gamasid mite faunas). Conceptual problems with the genus Iphidonopsis Gwiazdowicz, 2004 are reviewed, and a new combination, Iphidonopsis magnanalis (Ma & Yin, 1999) comb. n., is presented for Iphidozercon magnanalis Ma & Yin, 1999 from China. The genus Diseius Lindquist & Evans, 1965 is provisionally moved from the family Ascidae to the Digamasellidae. A new key to the genera of Arctoseiinae is presented.

Introduction

The subfamily Arctoseiinae at present numbers ca 90 species (including 19 undescribed species at hand of the genus Thor, 1930), among which approximately one-third (30 species, 26 – ) inhabit Arctic landscapes (Makarova 1999, in press). The separate local faunas within the Arctic include 5–16 arctoseiine species which constitute 26–83 % of the local gamasid mite diversity (Makarova 2012, in press). In this communication we account for a recently discovered, undescribed species with a unique combination of attributes that defies its placement in any of the five, currently recognized genera of Arctoseiinae Evans, 1963. We present a diagnosis of the subfamily, which argues for placement of the new genus in it, a description of the new genus, and detailed descriptions and illustrations of adult female and male of the new species. Previous confusion and disparity concerning the genus Gwiazdowicz, 2004 is considered. The monobasic genus Lindquist & Evans, 1965, previously allocated by various authors to either the Arctoseiinae or the Ascinae of the family Ascidae, is tentatively moved to the Digamasellidae.

Material and methods

Setal notation for the idiosoma follows Lindquist and Evans (1965), with some modification (Lindquist 1994). The leg and palpal chaetotaxy complies with Evans (1963, 1964). The poroidotaxy and adenotaxy are given according to Johnston and Moraza 1991, with small modification (Makarova 2003). The length of all shields was measured along the mid-line, and the width at the broadest part (in case of sternal/sternitigenital shield, the width was accepted as the distance between gland openings gvb; see Fig. 15). The length of the epigynal shield was measured to include the anterior flap, and the greatest width at the posterolateral corners. The length of all legs and tarsi are given excluding the ambulacrum, and also its pedicel on leg I. The subcapitulum length was measured from its anterior margin excluding projections (internal malae, corniculi). The measurements were carried out on all available specimens and their limits are stated in micrometers (μm). The following ratios were used in the description (Makarova 2000):

Figures 11–18.

gen. et sp. n., female 11 antaxial view of palpal tarsus and tibia 12 idiosomal venter 13–16 variants of sclerotization of pericoxal region II 17 tritosternum 18 pericoxal region IV. Scales: 11, 17, 18 – 25 μm, 12–16 – 50 μm.

lD/wD

the length-to-width ratio of the dorsal shield;

lSt/wSt, lVA/wVA

the length-to-width ratios of the sternal (in females) and ventrianal (in females and males) shields respectively;

lCh/lD

the ratio of the lengths of the movable cheliceral digit and the dorsal shield, %;

lCh/lCo

the ratio of the lengths of the movable cheliceral digit and the corniculus.

In the male description, the features common with the female are omitted.

Holotype and most of paratypes are deposited in Zoological Institute, Russian Academy of Sciences (ZIRAS), St.-Petersburg; part of paratype series (6 females and 1 male from Suntar-Khayata Range) in Canadian National Collection of Insects and Arachnids, Ottawa (CNC).PageBreak

Taxonomy / Systematics

Subfamily Arctoseiinae Evans, 1963

The Arctoseiinae was first proposed by Evans (1963) in a rather informal manner, based on the results of his observations on the chaetotaxy of the legs among a wide variety of free-living Gamasina. It was based on a reduced chaetotaxy of the genu and tibia of legs II to IV, and “the nature of the chaetotaxy of the opisthonotal region of the dorsal shield in the female.” A formal and more detailed description of the subfamily, including a key to its genera was presented by Lindquist and Evans (1965). From that description, the subfamily may be based on the following apomorphic characteristics within the family Ascidae:

Dorsal shield of adults entire, with or without lateral incisions; opisthonotal region usually with maximum of four pairs of lateral S setae, S2 usually not added in change from larva to protonymph. Marginal (r-R) series of setae lacking r6 in podonotal region and often R6 posteriorly; marginal R setae on lateral soft cuticle on female, but variably on dorsal shield margin on male. Submarginal (UR) setae absent. Female sternal shield with third pair of lyrifissures on its posterior margin; fourth pair of sternal setae on soft cuticle. Sternal setae st5 usually on soft cuticle flanking female epigynal shield. Male sternitigenital shield free from, but sometimes abutting ventrianal shield, and often not fully integrated with endopodal strips alongside coxae III–IV. Maximum number of setae on genua I–II–III–IV, respectively, 12-10-8-7; on tibiae, 12-9-7-7; in change from protonymph to deutonymph, seta pd-3 not added to genu and tibia I, pl-2 not added to genu and tibia II, and al-2 not added to genua and tibiae III–IV.

Plesiomorphic attributes of the Arctoseiinae include the following:

Gnathotectum basically bi- or tri-ramous, each process simple or denticulate; cheli- ceral movable digit bidentate in female, unidentate in male, without pointed process on mid-ventral surface, and with fringed arthrodial envelope basally; cheliceral fixed digit with small, setiform pilus dentilis, with usually few teeth restricted to apical half of masticatory surface, and without hyaline serrate rim near base on paraxial surface. Tarsus I usually with a conspicuously lanceolate-tipped seta dorsodistally. In change from protonymph to deutonymph, seta ad-3 added to genua I–II and tibia I, ad-2 added to tibia II, and al-2 added to tibia II.

gen. n.

urn:lsid:zoobank.org:act:271F12C1-9B82-44F6-BD00-B29F44B05C39

http://species-id.net/wiki/Maxinia

Type species.

new species. Monotypic. Genus based on adult female and male material representing one newly described species.

Diagnosis.

Adults of are immediately distinguished from those of other arctoseiinae genera by having a broad, robust dorsal shield; by the female having an PageBreakapomorphically expansive ventrianal shield that encompasses the metapodal plates anterolaterally and includes setae JV1 anteriorly; and by the male having an expansive sternitigenital shield that is fully consolidated with the endopodal strips beside coxae III–IV and abuts an expansive ventrianal shield. In addition, apomorphically, the subcapitulum has a narrow deutosternal groove, and the opisthogaster lacks a setal pair ZV1. None of the setae on tarsi II to IV are conspicuously differentiated by thinness, elongation, or curved shape. As in Thor, 1930 and Berlese, 1903, genu III carries only seven setae (lacking pv-1) on adults; however, adults of those genera have less robust, parallel-sided dorsal shields, retain opisthogastric setae ZV1, and their females have free metapodal plates and an anal shield. As in Hull, 1918, adults have robustly sclerotized dorsal and ventral shields. However, adults of have two to several pairs of dorsal shield setae (at least s4 and Z5) uniquely paddle-like in form, retain opisthogastric setae ZV1, eight setae (including pv-1) on genu III, and the female ventrianal shield is never expansive enough to include the metapodal plates and setae JV1; also, their tarsi II to IV have dorsal proximal setae ad-2, pd-2 conspicuously elongated and curved.

Description.

Idiosomal dorsum. Dorsal shield relatively broad, entire, without lateral incisions, well sclerotized; surrounding soft integument smoothly striate; all dorsal shield setae simple, undifferentiated in form; opisthonotal region lacking setae S2 (Fig. 9). Dorsal shield with complement of 20 pairs of discernible pore-like structures, of which 4 pairs superficially appear secretory (glandular). Marginal r-R series of setae on soft integument in female (Fig. 12), but on dorsal shield edge in male (Fig. 22); r-series lacking r6, R-series with R1-6; submarginal UR-setae absent. Peritrematal shields uniting with dorsal shield anteriorly and pericoxal strip beside coxa IV posteriorly (Fig. 10). Peritremes somewhat reduced in length.

Figures 3–10.

gen. et sp. n., female 3 tarsus II 4–7 gnathotectum 8 subcapitulum 9 dorsal shield 10 peritrematal shield. Scales: 3–8 – 25 μm, 9, 10 – 50 μm.

Figures 19–28.

gen. et sp. n., female (19–21) and male (22–28) 19 paraxial view of chelicera 20 antaxial view of chelicera 21 inner part of spermathecal apparatus 22 idiosomal venter 23 antaxial view of chelicera 24 subcapitulum 25 variant of form of posterior margin of sternitigenital shield 26–28 gnathotectum. Scales: 19, 20, 23, 24, 26–28 – 25 μm, 21, 22, 25 – 50 μm.

Idiosomal venter.Tritosternum with laciniae free for most of length (Fig. 17). Ventral shields well sclerotized and ornamented (Figs 1, 2, 12, 22). Female sternal shield entire, continuous with well developed endopodal extensions between coxae I–II, but free from those between coxae II–III (Figs 13–16); endopodal extension between I–II with gland pore apically where approaching or abutting exopodal strip; sternal shield with three pairs of sternal setae and three pairs of poroids; setae st4 isolated on soft cuticle. Female with well developed endopodal strips alongside coxae III–IV. Female epigynal shield widened behind level of setae st5, its posterior margin broadly convex and nearly abutting ventrianal shield; setae st5 and paragenital poroids iv5 on soft cuticle; postgenital furrow with two pairs of small platelets. Female with expansive ventrianal shield encompassing metapodal plates anterolaterally and including setae JV1 anteriorly, along with other opisthogastric and circumanal setae, except JV5, ZV4 on soft cuticle; ventrianal shield with paranal setae inserted at level of anterior margin of anus, with gland pores gv3 on posterolateral margins, and with cribrum formed as partitioned strip behind level of postanal seta. Male with expansive sternitigenital shield consolidated with presternal platelets and endopodal strips alongside coxae I–IV and abutting expansive ventrianal shield. Male ventrianal shield similar in expansiveness, setation, and other structure to that of female (Fig. 22); setae JV5, ZV4 onPageBreak soft cuticle, ZV5 absent. Peritrematal shield consolidated with exopodal strips behind coxae IV, with two poroids and one gland pore in area behind stigma, and a gland pore and poroid at level between coxae II–III; exopodal strip alongside coxae II–III usually fragmented.

Figures 1–2.

gen. et sp. n., ventral view 1 female 2 male.

Gnathosoma. Gnathotectum with basically but variably triramous anterior margin (Figs 4–7, 26–28); dorsal face without punctate fields. Chelicerae without any conspicuous process along antiaxial or paraxial lateral surfaces basal to digits (Figs 19, 20, 23); fixed digit with small, setiform pilus dentilis and series of teeth along distal half of masticatory surface; movable cheliceral digit bidentate on female (Fig. 19), unidentate on male (Fig. 23), with arthrodial envelope margin fimbriate; male spermatodactyl simple, digit-like, not recurved basally. Deutosternal groove narrow (Fig. 8), with seven transverse rows of denticles of similar width, rows variably denticulate (2–7 denticles), all rows connected by lateral margins. Corniculi normal in form, parallel in anterior projection from base to apex; internal malae normal in form, similar in length with corniculi or somewhat longer. Subcapitular setae smooth, not greatly disparate in length, hp1 not elongated. Palpi with normal setation as described for Gamasina by Evans (1964); palpfemoral seta al and palpgenual setae al-1 and al-2 more or less spatulate distally; palptarsal apotele two-tined.

Legs. Legs I to IV with ambulacrum bearing paired claws without basal swelling (Fig. 3), with paradactyli and rounded pulvilli, ambulacrum I smaller than ambulacra II–IV; legs I–IV similar in thickness, and not disparate in length. Legs II–IV with tarsus (excluding ambulacrum) less than twice as long as tibia. Tarsus I without a sensilla distinguishable as s by apically lanceolate form (as found in most other members of subfamily), and without markedly elongated setae apically, but with seven finger-shaped sensillae of different lengths. Tarsi II–IV with apical setal processes inconspicuous, shorter than ambulacrum (to base of claws), and with acutely triangular apical process ventrally. Complement of setae on segments of legs I–II–III–IV typical for Arctoseiinae as presented by Lindquist and Evans (1965): femora (2-5/3-2) (2-5/3-1) (1-3/1-1) (1-3/1-1) [Setation of femur III was mistakenly presented as 1-4/1-0 in Lindquist and Evans 1965 (see Evans 1963).]; genua (2-3/2, 2/1-2) (2-3/1, 2/1-1) (1-2/1, 2/0-1) (1-2/1, 2/0-1); tibiae (2-3/2, 2/1-2) (2-2/1, 2/1-1) (1-1/1, 2/1-1) (1-1/1, 2/1-1); in transformation from proto- to deutonymph, seta pd-3 not added to genu and tibia I, pv-1 but not pl-2 added to genu II, and al-2 not added to genua and tibiae III–IV (this combination of hypotrichy is apomorphic for subfamily). Leg setae collectively smooth; none of setae on tarsi II–IV conspicuously differentiated by thinness, elongation, or curved shape. Legs of male without dimorphically modified setae.

Etymology.

The name of the genus is tribute to the first author’s spouse, Maxine Lindquist. Together with him for 55 years, she supported his acarological endeavors, accompanied him in field work throughout North America, and hosted many visiting colleagues at home. The name is feminine in gender.

Remarks.

Among some of the characteristics that distinguish them from other taxa of Arctoseiinae, adults of resemble those of the genus Evans, 1957, Ascinae, e.g., the relatively broad, well sclerotized dorsal shield, expansive venPageBreaktrianal shield encompassing the metapodal plates and insertions of setae JV1, absence of setae ZV1, expansive male sternitigenital shield, and the narrow rows of deutosternal denticles. However, adults of present dorsal shield setation and leg chaetotactic attributes typical of the subfamily Ascinae, and are characterized by different distinctive attributes, including absence of paravertical setae z1, absences of setae av-2 on genu I and ad-2 on tibia II, gnathotectum with convex, smooth anterior margin, female with most or all of r-R marginal series of setae on margins of dorsal shield, female sternal region with setae st1 on separate presternal plates, and female epigynal shield apomorphically widened to include the paragenital poroids as well as setae st5 (Lindquist and Evans 1965, Athias-Henriot 1973).

sp. n.

urn:lsid:zoobank.org:act:33101F8A-830E-4F42-958D-FCFB74C3769D

http://species-id.net/wiki/Maxinia_arctomontana

Figs 1 35

Figures 29–34.

gen. et sp. n., protonymph (29–31) and larva (32–34) 29 idiosomal dorsum 30 gnathotectum 31 idiosomal venter 32 idiosomal venter 33 gnathotectum 34 idiosomal dorsum. Scales: 29, 31, 32, 34 – 50 μm, 30, 33 – 25 μm.

Figure 35.

Records of gen. et sp. n.

Material.

Holotype, female: EAST SIBERIA, YAKUTIYA, Suntar-Khayata Range, upper reaches of Kyubyume R., 63°13'N, 139°36'E, 1850 m a.s.l., SW slope, bird outlook with gramineous vegetation, 19.VII 2002, O.L. Makarova (ZIRAS).

Paratypes: 16 females, 3 males with same data as for holotype (ZIRAS); 6 females, 1 male, the same district, 1600 m a.s.l., snowbed, litter under , 29.VII 2002, O.L. Makarova (CNC); MAGADAN REGION, 8 females, 2 males, 3 protonymphs, 1 larva, Olskoye Plateau, upper reaches of Ola R., 1149 m a.s.l., snowbed, litter under , 10.VIII 2011, O.L. Makarova (ZIRAS).

Other material: YAKUTIYA, 3 females, vicinity of Ust-Nera settlement, 1400 m a.s.l., litter under , 26.VII 1992, M.B. Potapov; 1 female, Khalerchinskaya Tundra, 69°24'N, 158°37'E, VIII 1991, O.V. Starikova; 4 females, mouth of Kolyma R., 69°32'N, 160°44'E, Pokhodskaya Yedoma, dwarf shrub (, sp.) thicket, 18–19.VII 1994, A.B. Babenko; 2 females, delta of Yana R., Shirokostan Peninsula, vicinity of Ledyanoye Lake, community on south slope of valley, 4–6.VIII 1994, A.B. Babenko; 2 females, the same district, date and collector, forb-grassy meadow; MAGADAN REGION, 6 females, 1 male, upper reaches of Kolyma R., Aborigen Mt., thicket within icing in valley, litter, 23.VIII 2006, A.A. Alfimov; TAYMYR PENINSULA, 1 female, vicinity of Pyasino Lake, Nyapan’ Upland, -community on hill, 10.VII 1999, O.L. Makarova; 1 female, vicinity of Ragozinka R., 72°57'N, 80°56'E, “lemming hay” on slope, 10.VII 1983, A.B. Babenko; 1 female, mouth of Tareya R., hummocky tundra, 28.VII 2010, O.L. Makarova; 3 females, 3 protonymphs, 72°50'N, 101°15'E, bank of Zakharova Rassokha R., mossy tundra, 3.VII 2011, A.V. Barkalov; YAMAL PENINSULA, 2 females, Seyakha Lake, tundra, litter, 9.VII 1986, V.I. Bulavintsev; 1 female, Yakhadyyakha R., 72°53'N, 70°56'E, lemming hill with , 21.VIII 1994, A.B. Babenko; VAIGATCH ISLAND, 1 female, VII 1984, V.I. Bulavintsev; SOUTH SIBERIA, 5PageBreak females, Rudnyi Altai Mts., Ivanovskyi Belok Mt., 3.VII 1983, I.P. Vtorov; 1 female, West Sayan Mts., Alashskoye Upland, 2200 m a.s.l., -community, 20.VII 2001, S.K. Stebaeva; 2 females, the same region, vicinity of Sut-Khol Lake, --mosses-community, 27.VII 2001, S.K. Stebaeva.

Middle-sized dark-yellow or brownish mites with rather broad, somewhat pyri-form idiosoma (Figs 1, 2). Idiosomal shields well sclerotized, very finely punctate, with clearly reticulate ornamentation on nearly all surfaces except peritrematal plates. Many setae of body and appendages with fine, hair-like tips, which often are broken off. Dorsal shield rather broad, covering entire dorsal idiosoma, without lateral incisions.

Idiosomal dorsum. Dorsal shield 448–520 × 296–356, moderately broad, lD/wD ca 1.34–1.62, its maximal width at level of setae S1 (Fig. 9). Podonotal region normally with 18 pairs of simple setae (s1, s2, z1 sometimes symmetrically or asymmetrically absent). Opisthonotal region with 14 pairs of setae (S2 always absent). Among podonotal setae z1, s1, s2 distinguished by much shorter length (7–11), length of j1,2 18–26, other setae 22–36. On opisthonotal region setae J1-4 (20–28) shorter than others (30–44), and J5 clearly shortest (11–15). Dorsal shield with 4 pairs of cuPageBreakPageBreaktaneous glands gdj4, gdz6, gdZ3 and gdZ4. All marginal setae on soft cuticle (Fig. 12); 4 setae in series r (their length 16–24), 6 setae in series R (22–38); marginal poroid Rp in usual position between setae R3 and R4.

Idiosomal venter. Base of tritosternum narrow (18–22 × 11–14); laciniae with sparse large barbs, free for nearly entire length, fused basal area broadest, with short spicules (Fig. 17); length of lacinia free part 68–78. Presternal platelets 10–16 × 20–24, distinct, lineate, clearly separate from sternal shield (Fig. 12). Sternal shield wider (100–124) than long (60–72), lSt/wSt 0.48–0.64, minimal width between coxae II 62–74; consolidated with endopodal platelets between coxae I–II but not between coxae II–III. Endopodal projections between coxae I–II strong, nearly straight, their posterolateral margin concave, apices encompassing opening of gland gvb, and abutting or uniting with exopodal extensions (Figs 13–16). Sternal shield entirely reticulated; anterior margin straight or slightly concave; posterior margin straight or slightly concave. Sternal shield with typical setae st1-3 (30–34) and lyrifissures iv1-3; rarely, vestiges of gland gv1 present, off posterior margin of sternal shield. Setae st4 (22–28) on soft cuticle. Free endopodal fragments between coxae II–III well sclerotized with angular inner margin. Endopodal strips between coxae III and IV free, well developed (Fig. 18), partly hidden under epigynal flap. Epigynal shield (116–132 × 80–116) distinctly reticulated (Fig. 12), broadly axe- or flask-shaped, with broadly convex hyaline flap not extending to sternal shield, and posterior margin broadly convex; lateral margins strongly widening behind level of setae st5, but st5 (24–28) and paragenital poroids iv5 remain on soft cuticle. Two openings of gland gv2 medially to coxa IV and on posterior margin of exocoxal strip behind coxa IV usually poorly visible (Fig. 18). Two pairs of postgenital platelets in fold of soft cuticle. Ventrianal shield expansive, fully reticulated, wider (224–280) than long (165–192), lVA/wVA 0.63–0.82, consolidated with metapodal platelet sigillae laterally; anterior margin broadly concave, nearly abutting epigynal shield; posterior margin broadly convex, with cribrum a narrow band subdivided along 8 small festoons. Ventrianal shield with 6 (JV1-4, ZV2, ZV3) opisthogastric setae, plus the circumanal setae; setae similar in moderate length (22–30); paranal setae (20–26) inserted at level of anterior margin of anus, and nearly as long as postanal seta (24–32); opening of gland gv3 inconspicuous. Setae ZV1 absent, and ZV4, JV5 on soft cuticle; JV5 rather long (32–40). Exopodal strip usually fragmented alongside coxae II–III, mostly contiguous with peritrematal shield but ending freely from it, with extension that abuts or merged with endopodal extensions between coxae I–II (Figs 13–16). Peritrematal shield rather wide (Fig. 10), its anterior end united with dorsal shield, its posterior edge connecting with exopodal platelet enveloping coxa IV posteriorly; lyrifissures ip1-3 and glands gp1-2present (Fig. 18). Peritreme slightly shortened (152–180 × 9–11), not extending beyond mid-level of coxa I anteriorly. Spermathecal apparatus of laelapoid form, without sclerotized sections (Fig. 21).

Gnathosoma. Gnathotectum basically triramous, with usually three short, denticulate processes (Figs 4–7), middle projection equal to or longer than lateral ones. Subcapitulum (Fig. 8) longer (98–116) than wide (71–80). Deutosternum with PageBreakPageBreak7 narrow, laterally adjoined rows of denticles (2–7 denticles in each row); groove width 8–9. Hypostomatic pair hp3 (39–44) longer than other subcapitular setae (22–30); all setae simple, attenuate. Corniculi of moderate length and width, 30–36 × 11–13. Internal malae slightly longer than corniculi, gradually tapering to tip, with lateral margins fimbriated basally. Chelicera not large (Figs 19–20), its length without basal segment 128–139; cheliceral digits of moderate size (48–57, lCh/lD 9.5–12.1 %), one and a half longer than corniculus (lCh/lCo 1.48–1.75). Fixed digit of chela ending in apical hook, masticatory surface with one subapical tooth and pilus dentilis in antaxial position and four denticles in paraxial position. Movable digit (44–55) slightly shorter than fixed one, bidentate. Palp length 156–175; internal seta of trochanter (28–32) longer than external seta (19–26); palp with typically specialized setae on femur (al) and genu (al1, al2) thick with oblique tip; palp tarsus without macroseta (Fig. 11).

Legs. Legs of moderate length (I 340–396, II 272–304, III 264–296, IV 336–372); leg I shorter than dorsal shield. Length of tarsi I 92–106, II 80–90, III 84–89, IV 102–124. Leg chaetome as described for genus. Setae of legs simple, generally of moderate length; tarsi II–IV each with dorso-proximal setae ad-2, pd-2 not elongated or curved, and with al-1, pl-1 not thinner or more elongated than adjacent setae. Ambulacrum I on pedicellate base, claws I (8–10) smaller than claws II–IV (12–15). Tarsus I distally with 7 rod-like solenidia, 5 of them inserted apically. Ambulacra of legs II–IV (length 24–30) with moderately long paradactyli (9–11) extending clearly beyond apices of claws. Tarsi II–IV with apical setae ad-1 and pd-1 shorter (8–12) than claws (Fig. 3). Four subapical setae on tarsi II–IV evenly distant from apex, almost of equal length, ventral setae av-1 and pv-1 slightly weaker and shorter (18–23) than lateral setae al-1 and pl-1 (20–27).

Idiosomal dorsum. Dorsal shield 396–424 × 236–276, narrower than in female (lD/wD ca 1.50–1.75), fully reticulated, with all r-R marginal setae (10 pairs) on shield, such that podonotal region with 22 pairs of setae, including r2-5, and opisthonotal region with 20 pairs of setae, including R1-6 (S2 always absent). Relative lengths of setae as on female.

Idiosomal venter. Tritosternum base (12–16 × 10–12) shorter than in female (Fig. 22). Presternal platelets connected with sternitigenital shield. Sternitigenital shield fully united with endopodal platelets developed between coxae I–II, coxae II–III, and coxae III–IV, its posterior margin sometimes with pair of indentations (Fig. 25); length of shield 136–158, width between gvb openings 92–110, width at midlevel of coxae II 64–72, width at midlevel of coxae IV 60–72. Sternitigenital shield fully reticulated, with setae st1-3 (24–30) longer than setae st4,5 (20–24), and with lyrifissures iv1,2; lyrifissures iv3 and vestiges of glands gv1 not discernible. Ventrianal shield abutting but free from sternitigenital and peritrematal shields, fully reticulated, expansive, slightly wider (194–224) than long (176–202), yet narrower than in female, lVA/wVA 0.82–0.98, consolidated with metapodal platelet sigillae laterally; anterior margin straight or slightly concave, posterior margin and cribrum formed as in female. Ventrianal shield with setation and form, placement, and lengths of setae as in female, except JV1 more removed from anterior margin and poroids iv5 present on shield. Setae ZV1 absent, ZV4 and JV5 on soft cuticle.

PageBreakPageBreakGnathosoma. Apices of gnathotectum similar to female but sometimes variously shaped in different ways (Figs 26–28). Corniculi and internal malae as in female (Fig. 24). Cheliceral digits (38–43, lCh/lD 9.1–10.7 %) longer than corniculus (30–32 × 11–12, lCh/lCo 1.22–1.34). Fixed digit with dentition similar to female (Fig. 23) except smaller number of denticles in paraxial row (2–3). Movable digit with one large denticle and simple, closed, trough-like spermatodactyl (length of free part 22–24), protruding shortly beyond tip of digit.

Legs. Length of legs I–IV 344–376, 272–284, 256–264 and 320–340 respectively; length of tarsi I–IV 96–101, 78–80, 76–80 and 100–112 respectively. Legs without dimorphically modified setae.

Unknown.

. Idiosomal dorsum. Idiosoma 304–320 × 185–212. Podonotal shield 188–200 × 176–184, reticulate, with 11 pairs of setae (Fig. 29) and no less than 5 pairs of pore-like structures including opening of gland gdj4. Pygidial shield 54–76 × 160–164, reticulate, with 8 pairs of setae and openings of glands gdZ3, gdZ4. Interscutal soft cuticle with 7 pairs of setae and 3 pairs of mesonotal sclerites, anterior sclerites bearing gland pores gdz6 and poroids idz6. Setae r2, r3, and r5 on lateral soft cuticle beside podonotal shield. All dorsal setae needle-shaped, their length 14–35, except J5 clearly shortest (7–8).

Idiosomal venter. Tritosternum as in adults (Fig. 31). Sternal shield poorly sclerotized, with 3 pairs of setae (20–24) and 3 pairs of lyrifissures; presternal platelets weakly developed. Seta st5 absent, but poroid iv5 distinct. Anal shield nearly circular, with paranal setae nearly as long as postanal seta, and usually with opening of gland gv3. Opisthogastric region with 2 pairs of fine medial sclerites, small (10–13 × 7–8) metapodal platelets, 4 pairs of setae and 5 pairs of poroids. Peritremes extending to posterior margins of coxae III.

Gnathosoma. Gnathosomal structures in general as in adults, tectum as in Fig. 30.

Legs. Leg chaetotaxy typical for protonymphs of Ascidae (Lindquist and Evans 1965).

Idiosomal dorsum. Idiosoma 260 × 180. Podonotal and pygidial shields smooth, bearing 9 and 4 pairs of needle-shaped setae, respectively (Fig. 34). Interscutal soft cuticle with 3 pairs of narrow sclerites and 4 pairs of setae. Pygidial shield bent caudally, so setae J5 and Z4 inserted on ventral surface.

Idiosomal venter. Tritosternum in general as in adults (Fig. 32). Intercoxal region without delineated sternal shield, with 3 pairs of setae (17–18), lacking lyrifissures but with typical subdermal pair of structures between bases of legs III. Ventral soft cuticle with transverse fold nearly delineating podosomatic from opisthogastric regions. Opisthogastric soft cuticle with typical 4 pairs of opisthogastric setae plus ventrolaterally displaced dorsal setae S4, S5, Z5. Anal shield (38 × 78), transversally oval, wider than long, with circumanal setae large, paranals (54) longer than postanal (36), and with gland opening gv3 nearly posterior to paranal setae; anal valves with tiny euanal setae; cribrum undeveloped.

Gnathosoma. Hypostome, gnathotectum (Fig. 33), chelicera similar to adults, setae hp-3 and pc absentPageBreakPageBreak.

Legs. Leg chaetotaxy typical for larvae of Ascidae (Lindquist and Evans 1965).

The species name indicates its geographical range.

Distribution.

At present known from zonal and mountainous tundra landscapes of West, Middle and East Siberian sectors (Fig. 35).

Ecology.

Recorded from dry and humid tundra sites, meadows including zoogenic ones (e.g. bird of prey outlooks) and shrub (, dwarf , ) communities.

Variability.

The species is rather stable morphologically. The variability concerns mainly the form of gnathotectum (Figs 4–7, 26–28), the degree of coalescence of endocoxal and exocoxal elements around coxa II (Figs 13–16), sometimes the symmetrical or asymmetrical absence of setae s1, s2, z1, and the numbers of denticles in the rows on the deutosternum (usually 2–5 or 3–7).

Discussion

Notes on two problematic genera of Arctoseiinae

Genus

In the following key, Gwiazdowicz, 2004 is treated in the original sense (Gwiazdowicz 2004) to include Gwiazdowicz, 2004 and PageBreak (Ma & Yin, 1999) comb. n. Subsequently, Gwiazdowicz (2007) broadened his concept of to accommodate other species (e.g., Berlese, 1921, Halbert, 1915) and thereby distinguished his genus from Thor, 1930, primarily on the dorsal shield of adults having lateral incisions in , and these lacking in . However, not only is the lack of such incisions a plesiomorphic character state, as presented in some other genera of Arctoseiinae, but the presence of lateral incisions varies greatly among species, and is even subject to geographical variability and sexual dimorphism among some species, in . So, Athias-Henriot (1959, 1961) reported the lack of lateral incisions on females of Willmann, 1949 from Corsica and Spain, although shallow ones are present in other parts of Europe. Observations by Lindquist (1964) also indicated these differences between some populations. Illustrations of (Berlese, 1917) by Bernhard (1963) show just the slightest of lateral incisions on females, and entire lateral margins on males. Also, since has been previously designated as type-species of the genus by Evans (1954), Gwiazdowicz’s placement of this species in would render this genus a junior synonym of . With added phylogenetic perspective, we continue to follow the previous concept of Lindquist and Evans (1965), such that the genus embraces and includes the species , , and . Adult females of are somewhat similar to those of and in retaining what may be considered to be an apomorphically reduced, deutonymphal form of anal shield. However, as indicated in the following key, the genus shares with and Lindquist & Evans, 1965 the apomorphic attribute of having dorsoproximal setae ad-2 and pd-2 of tarsi II to IV elongated, curved, somewhat whip-like, while retaining the plesiomorphic attribute of genu III having eight setae, including pv-1. In contrast, , and are plesiomorphic in having setae ad-2 and pd-2 of tarsi II to IV unmodified, but sharing the apomorphic attribute of genu III having seven setae, in absence of pv-1.

Genus

Provisionally, we exclude the monotypic genus Lindquist & Evans, 1965 from the Arctoseiinae and from the following key to its genera. Based exclusively on gnathosomatic and idiosomatic attributes, the type-species of this genus, Hirschmann, 1962, has been assigned to various genera as conceived by different authors’ concepts of the family Ascidae, i.e., to the genus (including , Berlese, 1916 and Athias-Henriot, 1961) sensu Hirschmann (1962), to the subgenus (including but excluding and ) by Bernhard (1963), and to the genus (including but excluding and ) by Karg (1971, 1993). Accounting for those attributes and additional ones of leg chaetotaxy, thePageBreak species was assigned to a separate, new genus and placed in the tribe Ascini of the subfamily Ascinae (separate from the subfamily Arctoseiinae), by Lindquist and Evans (1965). The chaetotaxy of the genu and tibia of legs III and IV of resembles that of genera of Arctoseiinae, but was excluded from the Arctoseiinae based primarily on the adult female having a fully divided dorsal shield, and having sternal setae st5 inserted on the edges of the epigynal shield, rather than on soft cuticle. However, new observations of female by one of us (EEL) revealed the unanticipated absence of setae al-3 and pl-3 on basitarsi III–IV, and also of pd-3 on basitarsus IV. The chaetotaxy of tarsi II to IV is extremely constant throughout the families of free-living Gamasina (Evans 1963). Losses of basitarsal setae on legs II to IV are not known to occur among species of Ascidae, but they have been noted sporadically in the Digamasellidae and Rhodacaridae (Lindquist 1975). Also, in the absence of j2, setae j3 are inserted relatively closely behind j1 in , much as in the digamasellid subgenus Chant, sensu Lindquist (1975). The subcortical habitat association of with scolytid beetles is in common with that of a variety of digamasellids. As adult females of are highly neotenous in both leg and dorsal idiosomal setation, the similarity of leg chaetotaxy on genua and tibiae II–IV with Arctoseiinae is thought to be convergent, and our new observations persuade us to place tentatively in the Digamasellidae instead of the Ascidae, until such time as additional attributes become available from description of the female spermathecal system and of attributes of the adult male.

1	Leg chaetotaxy reduced: seta pd-3 absent on genu and tibia I, pl-2 absent on genu and tibia II, al-2 absent on genua and tibiae III-IV (maximum number of setae on genua I to IV, 12-10-8-7; on tibiae I-IV, 12-9-7-7); adult dorsal shield entire, with or without lateral incisions; opisthonotal region of dorsal shield usually with 4 pairs of lateral setae (S2 usually absent, exception – some Xenoseius Lindquist & Evans, 1965)	Arctoseiinae (6 genera)...2
–	Leg chaetotaxy without above reductions: pd-3 present on genu and tibia I, pl-2 present on genu and tibia II, al-2 present on genua and tibiae III-IV (minimum number of setae on genua I to IV: 12-11-8-9; on tibiae I-IV: 12-9-8-10); adult dorsal shield entire or divided; opisthonotal region of dorsal shield usually with 5 pairs of lateral setae (S2 present)	Ascinae (11 genera)
2	Genu III usually with 8 setae (pv-1 present); tarsi II–IV each with dorso-proximal setae ad-2, pd-2 elongate, curved	3
–	Genu III with 7 setae (pv-1 absent); tarsi II–IV with dorso-proximal setae not elongate or curved	5
3	Female with broad anal shield bearing only three circumanal setae; subcapitulum with hypostomatic setae hp-1 only slightly elongated, about 1.2 as long as hp-3;dorsal shield without midlateral incisions	Iphidonopsis Gwiazdowicz, 2004
–	Female with ventrianal shield bearing 1–6 pairs of opisthogastric setae in addition to circumanal setae; subcapitulum with anterior pair of hypostomatic setae hp-1 conspicuously elongated, at least 1.5 as long as hp-3;dorsal shield with or without midlateral incisions4
4	Tarsus I without pretarsus and claws; setae j1 and z1 smooth or barbed and variable in length; all other dorsal setae simple, none paddle-shaped	Xenoseius Lindquist & Evans, 1965
–	Tarsus I with pretarsus and claws; setae j1 and z1 smooth, pointed, or j1 rarely paddle-shaped; some dorsal setae (at least s4 and Z5) always paddle-shaped	Zerconopsis Hull, 1918
5	Tarsi II–IV with 1 (al-1) or 2 (al-1, pl-1) dorso-lateral subapical setae very slender and elongate; vertex of dorsal shield strongly arched downward, setae j1 concealed from above; peritremes sharply recurved anteriorly; dorsal shield without midlateral incisions; palptarsus with macroseta	Iphidozercon Berlese, 1903
–	Tarsi II–IV with neither of dorso-lateral subapical setae slender and elongate; vertex of dorsal shield not strongly arched downward, setae j1 visible from above; peritremes not recurved anteriorly; dorsal shield with or without midlateral incisions; palptarsus without macroseta	6
6	Dorsal shield of adult with parallel sides, lightly to moderately sclerotized, with lateral incisions of deutonymph retained or obliterated on adult, in male sometimes bearing some marginal setae of series r but none of R (these free on soft cuticle in female); opisthogastric setae ZV1 present; female with anal shield distant from metapodal plates and setae JV1; male with sternitigenital shield incompletely consolidated with endopodal strips alongside coxae I–IV and abutting or removed from variably expansive ventral/ventrianal shielding	Arctoseius Thor, 1930
–	Dorsal shield of adult relatively broad, well sclerotized, entire, in male bearing all marginal r-R setae (these free on soft cuticle in female); opisthogastric setae ZV1 absent; both sexes with expansive ventrianal shield encompassing metapodal plates anterolaterally and including setae JV1 anteriorly; male with expansive sternitigenital shield fully consolidated with endopodal strips alongside coxae I–IV and abutting expansive ventrianal shield	Maxinia gen. n.