# A new subcortical mite, *Divilia orbiculata* n. sp. (Acari: Hemisarcoptidae), from Siberia based on adults and phoretic deutonymphs

Alexander A Khaustov, Vladimir A Khaustov, Pavel B Klimov

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Alexander A Khaustov, Vladimir A Khaustov, Pavel B Klimov. A new subcortical mite, *Divilia orbiculata* n. sp. (Acari: Hemisarcoptidae), from Siberia based on adults and phoretic deutonymphs. *Acarologia*, 2024, 64 (1), pp.123-137. 10.24349/c9a2-3j04 . hal-04416803

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# A new subcortical mite, *Divilia orbiculata* n. sp. (Acari: Hemisarcoptidae), from Siberia based on adults and phoretic deutonymphs

Alexander A. Khaustov<sup>a</sup>, Vladimir A. Khaustov<sup>a</sup>, Pavel B. Klimov<sup>b</sup>

## Original research

### ABSTRACT

We describe females, males and phoretic deutonymphs of *Divilia orbiculata* n. sp. (Hemisarcoptidae) collected under the bark of fallen birch twigs in Western Siberia in association with sordariomycete fungi. Adults were previously unknown in *Divilia* and we describe them for the first time. *Divilia oculata* Sevastianov, 1969, the type species of the genus *Divilia*, is redescribed based on the phoretic deutonymph (holotype).

**Keywords** Astigmata; Hemisarcoptoidea; systematics; morphology; Western Siberia

**Zoobank** http://zoobank.org/31585F66-FFF5-468C-9BCD-B70AB049A0F1

### Introduction

The family Hemisarcoptidae (Acari: Astigmata: Hemisarcoptoidea) has 11 genera and more than 30 species (Schatz *et al.* 2011). Of them, adults were described only for five genera: *Congovidia* Fain and Elsen, 1971, *Hemisarcoptes* Lignières, 1893, *Linobia* Berlese, 1884, *Nanacarus* Oudemans, 1902, and *Nanacaroides* Volgin and Mironov, 1979. Species of *Hemisarcoptes* are predators of armored scale (Diaspididae) insects and their eggs (Houck, OConnor 1990); species of *Nanacarus* and *Nanacaroides* often inhabit the spore tubes of polypore fungi (OConnor 2009); *Linobia coccinellae* (Scopoli) is a subelytral parasite of the chrysomelid beetle *Chrysomela populi*; and a species of *Congovidia* Fain and Elsen, 1971 was collected in the nest of a solitary wasp in Brazil (Fain, Camerik 1977). Most hemisarcoptid species were described based only on phoretic deutonymphs associated with various insects, mostly beetles. Species of *Hemisarcoptes* are phoretic under the elytra of coccinellid beetles of the genus *Chilocorus*, absorbing the host hemolymph through the anus while phoretic (Houck, Cohen 1995). The genus *Divilia* Sevastianov, 1969 has three described species, all known from phoretic deutonymphs only: *D. oculata* Sevastianov, 1969 (type species), *D. occidentalis* Fain, Hurst, Tweddle, Lachlan, Majerus and Britt, 1995 and *D. exigua* Fain, Hurst, Fassotte, Webberley, Sloggett and Majerus, 1997. *Divilia oculata* is known from ants *Lasius fuliginosus* and *Dolichoderus quadripunctatus* in Ukraine and *Formica polyctena* and *F. rufa* in western Russia (Sevastianov 1969); *D. occidentalis* was found phoretic on coccinellid beetles *Chilocorus renipustulatus* (Fain *et al.* 1995) in England and *Adalia bipunctata* in the Netherlands (Fain *et al.* 1997); and *D. exigua* was recorded from the coccinellid beetle *Vibidia duodecimguttata* in Poland (Fain *et al.* 1997). Furthermore, two unidentified species of *Divilia* have been recorded in bark beetle pheromone traps in Western Siberia (Khaustov *et al.* 2018).

Here, we describe a new species *Divilia orbiculata* based on adults and phoretic deutonymphs collected under the bark of fallen birch twigs in Western Siberia. This is the first

Received 28 July 2023
Accepted 04 January 2024
Published 16 January 2024

Corresponding author
Alexander A. Khaustov<sup>D</sup>:
alex1973khaustov@gmail.com

Academic editor
Akashi Hernandes, Fabio

https://doi.org/10.24349/c9a2-3j04

ISSN 0044-586X (print)
ISSN 2107-7207 (electronic)

<figure><img src="image_7.png" /></figure>

Khaustov A. A. *et al.*

Licensed under
Creative Commons CC-BY 4.0

OPEN ACCESS

<footnote><sup>a</sup>Tyumen State University, Tyumen, 6 Volodarskogo Str., 625003 Russia.</footnote>

<footnote><sup>b</sup>Purdue University, Lilly Hall of Life Sciences, G-225, 915 W State St, West Lafayette, Indiana 47907, USA.</footnote>
description of adults in this genus. We also redescribe the holotype of *Divilia oculata* (phoretic deutonymph).

## Material and methods

The mite specimens were collected under the thin bark of old birch twigs lying on the ground, in association with sordariomycete (pyrenomycete) fungi (Fig. 5). Some of collected mite specimens were cleared in lactic acid and mounted in Hoyer's medium. Several specimens were preserved in 96% ethanol for future molecular work. Mites were studied under a Carl Zeiss AxioImager A2 (Carl Zeiss, Germany) compound microscope with phase contrast and differential interference contrast (DIC) optics. Photos of mite colonies were taken with an Olympus OM-D Em-10 digital camera attached to a Discovery V8 (Carl Zeiss, Germany) stereomicroscope; slide-mounted mites were imaged using an AxioCam ICc5 (Carl Zeiss, Germany) digital camera. Images and drawings were processed in Adobe Photoshop using image stacks as the background. Idiosomal chaetotaxy follows Griffiths *et al.* (1990); the terminology of coxisternal setae follows Norton (1998); chaetotaxy and solenidiotaxy of appendages follow Grandjean (1946) and (1939) for palps and legs, respectively. All measurements are given in micrometers (µm) for the holotype, followed by the range for paratypes. Legs were measured from the base of trochanter to the distal part of tarsus, excluding pretarsus and claw.

## Systematics

### Family Hemisarcoptidae Oudemans, 1908

### Genus *Divilia* Sevastianov, 1969

Type species: *Divilia oculata* Sevastianov, 1969, by original designation.

**Diagnosis** — Adults (based on *D. orbiculata* n. sp.).

*Female.* Chelicera robust (Fig. 7A); movable and fixed digits with two teeth each; paraxial surface with two spiniform cheliceral processes; cheliceral seta (cha) short, needle-like. Subcapitulum with one pair of setae (h); gnathosomal supracoxal setae absent. Palps short; basal palpal segment with only one dorsal seta (sup), ventral seta (a) absent; palpal solenidion very small; palpal eupathidia (ul) not observed. Idiosoma egg-shaped, sejugal furrow weakly developed (Fig. 6). Ocelli present, situated anterolaterad setae si; prodorsal shield absent; supracoxal setae (scx) filiform, situated laterad small supracoxal sclerite. Idiosoma with 23 pairs of setae: vi, si, se, scx, $c_1$, $c_2$, $c_p$, $c_3$, $d_1$, $d_2$, $e_1$, $e_2$, $f_2$, $h_1$, $h_2$, $h_3$, $la$, $3a$, $4a$, $4b$, g, $ps_1$, and $ps_2$. Most of hysterosomal setae short, filiform; setae $h_3$ very long, whip-like. Three pairs of cupules: *ia*, *im* and *ih*; cupules *ip* absent. All legs very short, subequal in length, robust (Figs 8, 9); all tarsi lack claws. Legs setation: leg I: Tr 0, Fe 1 (vF), Ge 2(2) (cG, mG, $\sigma'$, $\sigma''$), Ti 1(1) (dT, $\phi$), Ta 8(4) (*d*, *f*, *la*, *wa*, *ra*, *p*, *q*, *s*, $\epsilon$, $\omega_1$, $\omega_2$, $\omega_3$); leg II: Tr o, Fe 1 (vF), Ge 2(1) (cG, mG, $\sigma$), Ti 1(1) (dT, $\phi$), Ta 8(1) (*d*, *f*, *la*, *wa*, *ra*, *p*, *q*, *s*, $\omega_1$); leg III: Tr 0, Fe 0, Ge 0, Ti 1 (kT), Ta 6 (*d*, *r*, *w*, *p*, *q*, *s*); leg IV: Tr 0, Fe 0, Ge 0, Ti 0, Ta 6 (*d*, *r*, *w*, *p*, *q*, *s*). Setae *p* and *q* on tarsi I-IV massive, spiniform, distinctly larger than spiniform seta *s*.

*Male.* Gnathosoma as in female. Idiosoma smaller and more flattened dorsoventrally than in female. Prodorsum with triangular prodorsal shield (Fig. 11A). Setae 4b modified into unpaired sucker; genital setae (g) represented by alveoli. Other character states as in female.

*Phoretic deutonymph.* Gnathosoma strongly reduced; subcapitulum and palps very short, only gnathosomal solenidia present. Prodorsal sclerite smooth; ocelli and underlying pigment spot well developed. Hysterosomal seta $c_1$ present. Setae $la$ and $3a$ absent or represented by alveoli; setae $4a$, $4b$ and *g* filiform. Tarsi I-III with claws. Legs setation: leg I: Tr 0, Fe 1 (vF), Ge 2(1) (cG, mG, $\sigma$), Ti 1(1) (dT, $\phi$), Ta 6(3) (*d*, *e*, *f*, *la*, *wa*, *ra*, $\epsilon$, $\omega_1$, $\omega_3$); leg II: Tr o, Fe 1 (vF), Ge 2(1) (cG, mG, $\sigma$), Ti 1(1) (dT, $\phi$), Ta 6(1) (*d*, *e*, *f*, *la*, *wa*, *ra*, $\omega_1$). In *Divilia occidentalis* and
*D. exigua*, tarsus IV has 4 setae; leg III: Tr 0, Fe 0, Ge 0, Ti 1 (*kT*), Ta 4 (*d*, *r*, *w*, *s*); leg IV: Tr 0, Fe 0, Ge 0, Ti 0, Ta 5 (*d*, *w*, *r*, *q*, *s*). Setae *d* of tarsi I and II foliate distally. Tibia and tarsus IV fused. Setae *d* and *w* of tarsus IV very long, whip-like; setae *d* IV thinner and distinctly longer than *w* IV (Fig. 18).

### *Divilia oculata* Sevastianov

*Divilia oculata* Sevastianov, 1969: 447.

(Figs 1–4)

<figure><img src="image_8.png" /><figcaption>**Figure 1** *Divilia oculata* Sevastianov, 1969, phoretic deutonymph (holotype): A – dorsum of body, B – venter of body. Legs not shown.</figcaption></figure>

### Redescription

**Phoretic deutonymph** — Body broadly ovate. Length of idiosoma 210, width 160. Length of gnathosomal solenidion ω 18.

*Idiosomal dorsum* (Figs 1A, 4A). Prodorsal and hysterosomal shields punctate, without striae or wrinkles. Cupules not observed. Supracoxal setae *scx* smooth, filiform subequal in length with setae *se*. All dorsal setae thin, filiform and pointed. Length of setae: *vi* 21, *si* 10, *se* 15, *scx* 16, *c*₁ 12, *c*₂ 13, *c*ₚ 11, *c*₃ 16, *d*₁ 8, *d*₂ 13, *e*₁ 12, *e*₂ 13, *f*₂ 10, *h*₁ 12, *h*₂ 12, *h*₃ 18.

*Idiosomal venter* (Figs 1B, 4B). Coxisternal fields smooth. Setae *1a* and *3a* absent. Anterior apodemes of coxisternal fields I fused to form sternum; an area of striate cuticle extending between posterior apodemes II; posterior apodemes II with surface sclerotization along 1/2 of length; apodemes III directed anteromedially, medial apices fused with posterior median apodeme by surface sclerotization; anterior apodemes IV fused with median apodeme; posterior apodemes IV underlying anterior margin of attachment organ; free end of median apodeme simple. Anterior and posterior suckers of attachment organ subequal. Anterior conoidal setae (*ps*₂) situated on the same transverse level as posterior suckers (*ad*₁+₂). Length of setae: *4a* 10, *4b* 30, *g* 9.
<figure><img src="image_9.png" /><figcaption>**Figure 2** *Divilia oculata* Sevastianov, 1969, phoretic deutonymph (holotype): A – right leg I, dorsal aspect, B – right leg II, dorsal aspect.</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>**Figure 3** *Divilia oculata* Sevastianov, 1969, phoretic deutonymph (holotype): A – right leg III, ventral aspect, B – right leg IV, ventral aspect.</figcaption></figure>

*Legs* (Figs 2, 3). Length of legs: I 83, II 82, III 43, IV 31. Leg I (Fig. 2A). Tibia with unusually long dorsodistal subtriangular projection. Solenidion ω₁ 14 digitiform, slightly thickened distally; solenidion ω₃ 9 baculiform; famulus ε small, spiniform, situated mesad solenidion ω₁; solenidion φ 44 attenuate; solenidion σ 5 baculiform. Setae cG, mG of genu, gT of tibia, and f of tarsus needle-like; setae vF of femur, d, la, wa, ra of tarsus filiform. Alveolae of solenidion ω₂ absent. Leg II (Fig. 2B). Tibia with unusually long dorsodistal subtriangular
<figure><img src="image_11.png" /><figcaption>**Figure 4** Phase contrast micrographs of *Divilia oculata* Sevastianov, 1969, phoretic deutonymph (holotype): A – dorsal view, B – ventral view.</figcaption></figure>

projection. Solenidion ω₁ 17 digitiform, slightly thickened distally; solenidion φ 40 attenuate; solenidion σ 6 baculiform. Setae cG, mG of genu, gT of tibia, and f of tarsus needle-like; setae vF of femur, d, la, wa, ra of tarsus filiform. Leg III (Fig. 3A). All setae smooth and pointed; seta s of tarsus spiniform, other setae filiform. Leg IV (Fig. 3B). Tarsus IV widened distally, with five setae; all setae filiform.

Other instars unknown.

**Material examined** — Phoretic deutonymph (holotype), Ukraine, Khmelnitsky Region, Chemerovetsky District, vicinity of Chemerovtsy settlement, on ant *Lasius fuliginosus*, 28 June 1959, V.D. Sevastianov. Housed at the Museum of Zoology, Odessa I. I. Mechnikov National University, Odessa, Ukraine.

**Remarks** — The original description of *Divilia oculata* is incomplete. The hysterosomal sclerite is depicted with numerous striae in the original description. However, we observed a smooth hysterosomal sclerite in the holotype (Fig. 4). Sevastianov (1969) reported *D. oculata* from different ant hosts in different regions (Western Ukraine, European Russia). It is likely that his concept of *D. oculata*, may involve more than one species. We examined several specimens of *Divilia* sp. collected from various ant species (mostly *Formica* spp.) from different localities in Russia having a striated hysterosomal sclerite. However, these phoretic deutonymphs clearly differ from *D. oculata* by other morphological characters.

**Divilia orbiculata n. sp.**

Zoobank: A757DF0F-B14C-47B5-8347-5FCE196C1B58

(Figs 5–18)

**Description**

**Female** — (Figs 6, 7A–C, 8, 9, 10A, 14A). Idiosoma (Figs 6, 7B, C, 10A, 14A). Length of idiosoma 415–455, maximum width 240–290.

An area between setae *vi* with very weak sclerotization. Supracoxal setae *scx* filiform, with slightly thickened basal half and with few weak barbs; Grandjean's organ simple and narrowly elongate (Figs 7B, 14A). Anterior apodemes of coaxal fields I fused medially in the
<figure><img src="image_12.png" /><figcaption>**Figure 5** *Divilia orbiculata* n. sp. colonies under the bark of birch twigs in association with sordar-iomycete fungi (A-D).</figcaption></figure>

<figure><img src="image_13.png" /><figcaption>**Figure 6** *Divilia orbiculata* n. sp., female: A – idiosoma in dorsolateral view, B – idiosoma in ventrolateral view.</figcaption></figure>
<figure><img src="image_14.png" /><figcaption>**Figure 7** *Divilia orbiculata* n. sp., female (A–C) and male (D): A – chelicera, paraxial view, B – supracoxal seta and Grandjean's organ; C – spermatheca; D – gnathosoma, ventral aspect.</figcaption></figure>

<figure><img src="image_15.png" /><figcaption>**Figure 8** *Divilia orbiculata* n. sp., female: A – left leg I, dorsal aspect, B – left leg II, dorsal aspect.</figcaption></figure>
<figure><img src="image_16.png" /><figcaption>**Figure 9** *Divilia orbiculata* n. sp., female: A – left leg III, dorsal aspect, B – left leg IV, dorsal aspect.</figcaption></figure>

form of a Y. Posteromedial extensions of anterior apodemes of coxal fields I recurved laterally. Posterior apodemes of coxal fields I fused posteromedially with anterior apodemes of coxal fields II. Anterior apodemes of coxal fields II thickened, spiked anteromedially and recurved posteromedially. Posterior apodemes of coxal fields II absent. Anterior apodemes of coxal fields III and IV arched anteromedially. Posterolateral extension of anterior apodemes of coxal fields III and IV hooked. Posterior apodemes of coxal fields III and IV absent. A pair of small sclerites situated anteriad setae *c*₃. Anus and ovipore contiguous, posteriad to coxal fields IV. Genital papillae internal to inverted V-shaped genital opening. Setae *ps*₁ and *ps*₂ subequal in length, flanking ovipore. Spermatheca (Fig. 7C) funnel-shaped, slightly asymmetrical, with a pair of cup-shaped sclerites and long duct. Length of idiosomal setae: *vi* 13–15, *si* 16–18, *se* 55–60, *scx* 24–27, *c*₁ 12–15, *c*₂ 12–15, *c*ₚ 14–17, *c*₃ 16–19, *d*₁ 13–17, *d*₂ 15–19, *e*₁ 13–18, *e*₂ 17–22, *f*₂ 21–24, *h*₁ 23–26, *h*₂ 22–26, *Ia* 19–22, *3a* 18–21, *4a* 12–15, *4b* 13–16, *g* 15–17, *ps*₁ 13–15, *ps*₂ 15–17. Setae *h*₃ very long and thin (not measured).

Legs (Figs. 8, 9). Length of legs: I 68–77, II 64–67, III 60–72, IV 58–67. Leg I (Fig. 8A). Solenidion ω₂ very short (1–2), difficult to see, adjacent to short and thick spiniform famulus ε; solenidion ω₁ 9–10 digitiform, slightly widened distally; solenidion ω₃ 11–12 baculiform; solenidion φ 35–37 attenuate; solenidia σ' 7–8 and σ'' 11–12 adjacent, digitiform. Setae *vF, d, la, ra* and *wa* long, filiform; setae *cG, mG* of genu, *gT* of tibia and *f* of tarsus short, needle-like; seta *s* of tarsus spiniform; setae *p* larger than *q*, both very thick, slightly hooked distally. Anterolateral surface of trochanter with two weakly sclerotized tooth-like projections. Leg II (Fig. 8B). Solenidion ω₁ 10–11 digitiform, slightly widened distally; solenidion φ 27–30 attenuate; solenidion σ 4–5 digitiform. Setae *vF, d, la, ra* and *wa* long, filiform; setae *cG* and *mG* of genu, *gT* of tibia and *f* of tarsus short, needle-like; seta *s* of tarsus spiniform; setae *p* larger than *q*, both very thick, slightly hooked distally. Leg III (Fig. 9A). Setae *d, w* and *r* of tarsus long, filiform; seta *kT* of tibia short, needle-like; setae *p, q* and *s* subequal, very thick, spiniform, slightly hooked distally. Leg IV (Fig. 9B). Setae *d, w* and *r* of tarsus long, filiform; setae *p, q* and *s* subequal, very thick, spiniform, slightly hooked distally.

**Male** — (Figs 7D, 10B, 11–13, 14B–D). Idiosoma (Figs 10B, 11, 14B–D). Length of
idiosoma 265–285, maximum width 160–165. Prodorsal shield well sclerotized, about twice
longer than wide (Fig. 14B). Ventral apodemes similar to those of female, except presence of
short posterior apodemes of coxal fields II and IV. Genital area with weakly sclerotized sclerite
(Fig. 14C). Aedeagus short and S-shaped (Fig. 14D). Length of idiosomal setae: *vi* 15, *si*
13–15, *se* 54–57, *scx* 19–21, *c*₁ 11–13, *c*₂ 11–14, *c*ₚ 16–18, *c*₃ 14–17, *d*₁ 13–16, *d*₂ 15–17, *e*₁
15–17, *e*₂ 12–15, *f*₂ 14–16, *h*₁ 17–20, *h*₂ 19–22, *la* 18–20, *3a* 18–20, *4a* 13–15, *ps*₁ 11–13, *ps*₂
12–13.

<figure><img src="image_17.png" /><figcaption>**Figure 10** Phase contrast micrographs of *Divilia orbiculata* n. sp.: A – ventrolateral view of female, B – ventral view of male.</figcaption></figure>

Legs (Figs. 12, 13) similar to those of female, except solenidion ω₂ well developed, digitiform, slightly widened distally and seta s of tarsi I and II only slightly thickened. Length of legs: I 63–64, II 56–64, III 49–52, IV 50–51. Length of solenidia: leg I: ω₁ 7, ω₂ 4, ω₃ 12–13, φ 28, σ' 5, σ'' 7–8; leg II: ω₁ 7, φ 24, σ 3–4.

**Phoretic deutonymph** — (Figs 15–18). Body broadly ovate. Length of idiosoma 210 (205–235), width 140 (135–160). Length of gnathosomal solenidion ω 18.

*Idiosomal dorsum* (Figs 15A, 18A). Prodorsal and hysterosomal shields punctate; hysterosomal shield with weak longitudinal wrinkles. Cupules *ia* located posterolaterad of setae *c*₂; cupules *ip* very small, located anterolaterad of setae *f*₂. Supracoxal setae *scx* smooth, filiform, longer than setae *se*. All dorsal setae thin, filiform and pointed. Length of setae: *vi* 13 (12–14), *si* 8 (8–10), *se* 9 (8–11), *scx* 14 (14–18), *c*₁ 7 (7–9), *c*₂ 8 (7–10), *c*ₚ 9 (8–11), *c*₃ 12 (12–13), *d*₁ 9 (8–10), *d*₂ 7 (7–9), *e*₁ 9 (9–12), *e*₂ 9 (8–11), *f*₂ 9 (8–11), *h*₁ 8 (8–9), *h*₂ 7 (7–9), *h*₃ 18 (15–20).

*Idiosomal venter* (Figs 15B, 18B). Setae 3a represented by alveoli. Other character states as in *D. oculata*. Length of setae: 4a 7 (7–8), 4b 13 (13–21), g 6 (6–10).

Legs (Figs 16, 17) very similar to those of *D. oculata*, except small alveola of solenidion ω₂ present anteromedially to solenidion ω₁, and triangular dorsodistal projections of tibiae I and II shorter. Length of legs: I 79 (78–89), II 77 (72–86), III 47 (44–50), IV 34 (33–36). Length of solenidia: leg I: ω₁ 10 (10–12), ω₃ 9 (9–11), φ 46 (46–50), σ 5 (4–6).
<figure><img src="image_18.png" /><figcaption>**Figure 11** *Divilia orbiculata* n. sp., male: A – idiosoma in dorsal view, B – idiosoma in ventral view.</figcaption></figure>

<figure><img src="image_19.png" /><figcaption>**Figure 12** *Divilia orbiculata* n. sp., male: A – left leg I, dorsal aspect, B – left tarsus I, ventral aspect; C – left leg II, dorsal aspect; D – left tarsus II, ventral aspect.</figcaption></figure>
<figure><img src="image_20.png" /><figcaption>**Figure 13** *Divilia orbiculata* n. sp., male: A – left leg III, ventral aspect, B – left leg IV, ventral aspect.</figcaption></figure>

<figure><img src="image_21.png" /><figcaption>**Figure 14** DIC micrographs of *Divilia orbiculata* n. sp., female (A) and male (B-D): A – supracoxal seta *scx* and Grandjean's organ; B – prodorsum; C – hysterosoma, ventral aspect; D – aedeagus, lateral aspect.</figcaption></figure>
<figure><img src="image_22.png" /><figcaption>**Figure 15** *Divilia orbiculata* n. sp., phoretic deutonymph (holotype): A – dorsum of body, B – venter of body. Legs not shown.</figcaption></figure>

<figure><img src="image_23.png" /><figcaption>**Figure 16** *Divilia orbiculata* n. sp., phoretic deutonymph (holotype): A – right leg I, dorsal aspect, B – right leg II, dorsal aspect.</figcaption></figure>
<figure><img src="image_24.png" /><figcaption>**Figure 17** *Divilia orbiculata* n. sp., phoretic deutonymph (holotype): A – right leg III, ventral aspect, B – right leg IV, ventral aspect.</figcaption></figure>

<figure><img src="image_25.png" /><figcaption>**Figure 18** Phase contrast micrographs of *Divilia orbiculata* n. sp., phoretic deutonymph (holotype): A – dorsal view, B – ventral view.</figcaption></figure>

**Type material** — Phoretic deutonymph (holotype), slide ZISP S-Hms-1, Russia, Novosibirsk Region, vicinity of Novosibirsk, 54°49′44.7″N 83°14′21.1″E, colonies of sordariomycete fungi, under thin bark of fallen birch twigs, on ground; 22 October 2022, collected by Aiji A.I. (twigs) and Khaustov V.A. (mites); paratypes: 12 females, 3 males, 5 phoretic deutonymphs,
same data.

**Type deposition** — The holotype, two paratype phoretic deutonymphs, 2 paratype females and 1 paratype male are deposited in the mite collection of the Zoological Institute of RAS, Saint Petersburg, Russia; other paratypes are deposited in the collection of the Tyumen State University Museum of Zoology, Tyumen, Russia.

**Etymology** — The name of the new species is derived from *orbiculatus* (round, having circular shape; Latin adjective, gender feminine) referring to the ball-shaped body of females.

**Differential diagnosis** — The phoretic deutonymph of the new species is similar to *Divilia oculata* in having solenidion σ on genu II well-developed, tarsus IV with five setae, and alveoli 1a absent. The new species differs from *D. oculata* in having alveoli of setae 3a present (absent in *D. oculata*); dorsal hysterosomal sclerite with longitudinal wrinkles (without wrinkles in *D. oculata*); setae *se* and *si* are subequal and clearly shorter than *scx* (*se* longer than *si* and subequal with *scx* in *D. oculata*); and solenidion ω₁ on tarsus II (11–13) shorter than that in *D. oculata* (17).

## Acknowledgements

Authors would like to thank the volunteer Aiji A.I. (Novosibirsk, Russia) for collecting samples. This study was supported by the Ministry of Science and Higher Education of the Russian Federation within the framework of the Federal Scientific and Technical Program for the Development of Genetic Technologies for 2019–2027 (agreement № 075-15-2021-1345, unique identifier RF—193021X0012).

## ORCID

Alexander A. Khaustov ID https://orcid.org/0000-0002-0306-112X

Vladimir A. Khaustov ID https://orcid.org/0000-0003-2831-7213

Pavel B. Klimov ID https://orcid.org/0000-0002-9966-969X

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