Insectolaelaps diaperi Mašán, 2025, sp. nov.
Creators: name: Mašán, Peter
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Mesostigmata
Digamasellidae
Insectolaelaps
Insectolaelaps diaperi

description: Insectolaelaps diaperi sp. nov.
(Figures 14–27)
Diagnosis
Idiosoma broadly oval, with mostly strong, acicular and similarly long setae; setae j1, r2 and r3 on soft integument in deutonymph. Shield surface completely (dorsal and ventrianal shields, ventral shield of male) or only laterally reticulate (sternal and sternogenital shields), or punctate (anal shield) or smooth (genital shield, sternal shield of deutonymph). In females, sternal setae st1–st3 somewhat thicker than others, bases of st3 conspicuously close together; in deutonymph, st2 and st4 unusually placed on soft integument. Ventrianal shield with four pairs of opisthogastric setae (Jv1–Jv3, Zv2), strongly widened in anterior part, with distinct punctation near anus. Peritremes of adults short, reaching level between coxae II and III. Movable cheliceral digit with six to seven teeth in females and five to seven teeth in deutonymphs; male spermatodactyl thin, apically narrowed, moderately curved and longer than movable cheliceral digit. Genu III and tibia III with eight setae each; genu IV and tibia IV without conspicuously elongated dorsal setae. Male legs II and IV spurred, as in Figs 22A–C, 22E, 23; subapical spur of tarsus II well developed, with rounded apex.
Description
Female (Figs 14A, 15–17, 18C, 19A, 19B, 20A–20C, 21C, 27A). Dorsal idiosoma (Figs 14A, 15). Idiosoma 530– 660 μm long, 365–445 μm wide (n = 5), weakly dorso-ventrally flattened, elongate, suboval to obovate, completely covered by two dorsal shields. Podonotal shield 240–305 μm long, 350–440 μm wide, semicircular, strongly convex anteriorly, moderately curved laterally and almost straight or slightly convex posteriorly, with four weakly indicated medial scleronodules at level of setae r5, reticulate pattern on surface in anterior and lateral parts, and 22 pairs of setae (j1–j6, z1–z6, s1–s6, r2–r5). Opisthonotal shield 295–350 μm long, 350–440 μm wide, subpentagonal, widest at level between setae S1 and S2, with straight to slightly convex anterior margin, curved lateral margins slightly expanded ventrally, well-rounded posterior margin, reticulate surface and finely punctate medial area between setae J4 and J5; 20 pairs of opisthonotal setae, of which only R1 is located on the soft integument outside the shield. Most dorsal setae relatively stout, acicular and similar in length, except for short, needle-like setae z1 and J5 and elongate, whip-like setae Z5 and S5. Lengths of selected dorsal setae: j1 28–35 μm, j2 37–47 μm, j3 47–54 μm, j4 35–42 μm, j5 34–40 μm, j6 36–44 μm, z1 10–20 μm, z5 34–44 μm, s1 20 –29 μm, s5 and s6 54 –63 μm, r2 26–34 μm, r3 44–54 μm, J1 41–47 μm, J2 39–48 μm, J3 35–43 μm, J4 29–39 μm, J5 15–23 μm, Z1 57–63 μm, Z2 55–64 μm, Z3 39–46 μm, Z4 29–36 μm, Z5 125–175 μm, S1 50 –59 μm, S2 55 –66 μm, S3 49 –58 μm, S4 46 –52 μm, S5 140–190 μm, R1 25–35 μm, R2 25–33 μm, R3 27–38 μm, R4 29–37 μm, R5 32–40 μm.
Ventral idiosoma (Figs 16, 17). Tritosternum normal for the genus. Presternal plates weakly sclerotized, transversely striate and separately connected to anterolateral margins of sternal shield. Sternal shield shorter than wide, 68–85 μm long in its better sclerotized part, 98–115 μm wide at the narrowest part between coxae II, with well-developed anterolateral and lateral corners, straight medial anterior and deeply concave posterior margins; lateral surface reticulate or with longitudinal lines, medial surface smooth or sometimes with very faint reticulate pattern in its anterior part; four pairs of sternal setae (st1–st4) and three pairs of slit-like lyrifissures (iv1–iv3), of which st1 on weakly sclerotized anterior part of shield; sternal setae st1–st3 similar in length and thickness, slightly thicker than st4 and other ventral setae, with following distances between them: st3↔st3 (48–60 μm) ≤ st1↔st1 (55–69 μm) <st2↔st2 (92–104 μm) <st4↔st4 (105–112 μm). Epigynal shield elongate, 125–140 μm long, 105–125 μm at widest part behind genital setae (st5) and 76–86 μm at narrowest part in anterior part between coxae IV, with rounded hyaline anterior margin reaching level of setae st4, almost straight lateral and posterior margins, smooth surface, and a pair of setae on posterolateral margins; genital lyrifissures (iv5) on soft integument near posterolateral corners of shield. Ventrianal shield (Fig. 17) longer than wide, 223–255 μm long and 185–232 μm wide, convex anteriorly and posteriorly, concave laterally, conspicuously widened in anterior part and moderately narrowed in submedial or posterior part, normally with four pairs of opisthogastric setae (Jv1–Jv3, Zv2) in addition to three circumanal setae (in one female, as in Fig. 16, Zv3 also on ventrianal shield); almost entire surface reticulate except for punctate area in posteriormost part near anus; circumanal setae similar in length (ad 46–55 μm, pa 42–49 μm); posterior margin connected to opisthonotal shield, with cribrum having two or three transverse rows of denticles. Endopodal platelets III/IV free, small and subtriangular. Exopodal platelets fused into a narrow strips, free of peritrematal shields except for their posterior tips. Peritrematal shields narrow, free over almost entire length including poststigmatic part, connected to podonotal shield between setae r2 and r3; peritremes short, 115–135 μm long, with anterior tip between setae r3 and r4. Two pairs of metapodal platelets present; larger platelets narrow and long, 52–65 μm x 8–15 μm in size, more or less constricted in anterior part; smaller platelets suboval to irregularly shaped, 8–16 μm x 6–10 μm in size. Soft opisthogastric integument with three pairs of setae (Jv5, Zv1, Zv3). All sternal and opisthogastric setae with attenuated apical part and following lengths: st1 35–43 μm, st2 and st3 31–40 μm, st4 33–43 μm, st5 36–45 μm, Jv1 30–39 μm, Jv2 and Jv3 40–49 μm, Jv5 49–65 μm, Zv2 and Zv3 43–55 μm.
Sperm induction system (Fig. 21C). Normal for genus, with a pair of well-sclerotized spherical structures, each adjacent to inner margin of coxa IV and bearing two tubular processes; processes often variously curved, slightly thicker in the basalmost part, 45–62 μm long, and with short terminal parts usually insignificantly thickened and apically rounded.
Gnathosoma (Figs 14A, 18C, 19A, 19B, 20A–20C). Deutosternal furrow wide (Fig. 18C), with five transverse rows of many denticles connected laterally by undulate longitudinal lines; posteriormost row widest and extending well beyond longitudinal lines; corniculi well sclerotized and spaced, horn-like, slightly divergent to each other; internal malae apically pointed, with densely fimbriated outer margins and projecting beyond corniculi. Hypostomal setae smooth and needle-like; setae h2 shortest and h3 longest (h1 35–45 μm, h2 9–15 μm, h3 45–56 μm, pc 20–27 μm). Middle article of chelicerae relatively long and narrow, gradually widening proximally, 125–140 μm long (Figs 19A, 19B); movable digit 44–52 μm long, with well-developed terminal hook and usually six to seven teeth, including the largest with most proximal position; fixed digit with bidentate terminal hook, a small subterminal tooth and a laterally located row of three larger medial teeth and usually 2–4 minute proximal teeth; pilus dentilis short and thick; dorsal seta short, hyaline and barely observable; arthrodial membrane well developed, usually with a row of several spines near ventral base of movable digit. Anterior margin of epistome triramous; all processes similar in size, pointed and spiny in their apical part (Figs 20A–C).
Legs (Figs 14A, 27A). All legs shorter than idiosoma, with well-developed pretarsus and ambulacral apparatus including pulvillus and two claws; pulvillus and claws of legs I slightly smaller than those of other legs; legs I shorter or similar in length to legs IV; dorsal scutal surface of coxae I obliquely cleft, with an interspace of soft cuticle (seen in Fig. 14A) and a row of several denticles on anterior margin; anterior margin of coxae II with a sharp spine; legs I 410–455 μm, legs II 340–385 μm, legs III 330–405 μm, legs IV 410–495 μm long. Chaetotaxy of the legs: leg I—coxa (2), trochanter 1-1/3-1 (6), femur 2-3/1, 2/3-2 (13), genu 2-3/2, 2/1-2 (12), tibia 2-3/2, 2/1-2 (12); leg II—coxa (2), trochanter 1-0/3-1 (5), femur 2-3/1, 2/2-1 (11), genu 2-3/1, 2/1-2 (11), tibia 2-2/1, 2/1-2 (10); leg III—coxa (2), trochanter 1-1/3-0 (5), femur 1-2/1, 1/0-1 (6), genu 2-2/1, 2/0-1 (8), tibia 2-1/1, 2/1-1 (8); leg IV— coxa (1), trochanter 1-1/3-0 (5), femur 1-2/1, 1/0-1 (6), genu 1-2/1, 2/0-1 (7), tibia 1-1/1, 2/1-1 (7); tarsi II–IV with 18 setae; pv1 of genu III absent. Leg setae smooth and mostly needle-like, except for some slightly thickened dorsal setae of femora II–IV and genua III–IV, including spine-like seta pd2 on genua III and IV (Fig. 27A), conspicuously shortened and thickened apicoventral setae (av1, pv1) on tarsi II–IV, elongated and distally attenuated whip-like setae ad2 on tarsi II–IV (these ad2 with unusual perpendicular orientation to tarsal axis).
Male (Figs 14B, 18E, 19C, 19D, 20D–20F, 21A, 21B, 22, 23, 27B). Idiosoma 465–570 μm long, 335–420 μm wide (n = 6; Fig. 22D). Podonotal shield 230–290 μm long and 335–420 μm wide, laterally fused with peritrematal shield located ventrally at anterolateral margins; opisthonotal shield 245–295 μm long and 335–415 μm wide, extensively united laterally and posteriorly with ventral shield. All dorsal setae on podonotal and opisthonotal shields, including marginal setae R2–R5. Sternitogenital shield as in Fig. 21A, 210–235 μm long, with well-developed endopodal corners between coxae II–III and III–IV, reticulate pattern only on lateromarginal areas and four pairs of similar sternal setae (st1–st4 30–47 μm); genital setae (st5) on triangular plates adjacent to posteriormost part of sternitogenital shield, each plate with two or three longitudinal lines on outer surface and inner posterior margin connected to posterior margin of sternitogenital shield. Ventral shield with convex anteromedial margin, small notches behind coxae IV directed towards setae Zv1, and same number of opisthogastric setae as in female. Peritrema as in Fig. 21B. Gnathosoma relatively shorter and broader than in female (Fig. 18E), with similar features as in female, except for distance between corniculi (more distant in male) and width of deutosternal furrow in its anterior part. Length of rostral setae as follows: h1 36–43 μm, h2 10–14 μm, h3 45–50 μm, pc 19–27 μm. Middle article of chelicerae relatively shorter than in female and similarly thick over entire length, 103–112 μm long; movable digit 35–41 μm long, regularly curved, with well-developed terminal hook, large medial tooth and spermatodactyl; spermatodactyl thin and long (51–58 μm long), gradually narrowing towards apex, moderately curved, bluntly pointed, directed forward and upward, and extending far beyond terminal part of movable digit; sperm duct relatively broad, shorter than spermatodactyl (with opening in subapical part) and located approximately along the central axis of spermatodactyl; fixed digit with terminal hook, a distal tooth and small pilus dentilis placed on small projecting base (Figs 19C, 19D). Epistome as in Figs 20D–F, with shorter and wider processes than in female; central process sometimes conspicuously widened, and outer margins of lateral processes sometimes completely serrate. Legs II spurred (Fig. 23A): anteroventral seta of femur, genu, tibia and tarsus modified into a strongly sclerotized structure, formed as a robust and superficially striated spur (femur) or small and semiglobular tubercle (genu, tibia, tarsus); femur II with another ventrolateral medial projection; ventral telotarsus II with large convex protuberance in distal part, clearly more pronounced than that in proximal part (Figs 23B–D). Proximal segments of legs IV also spurred (Figs 22A–C): posteroventral distal margin of coxa with inconspicuous, rounded, petal-like projection (rarely formed as anteriorly directed spine), anterodistal margin of trochanter shaped into a small spine, and medial posteroventral surface of femur with conspicuous, bluntly pointed spur located on suboval or rounded base and usually directed towards distal margin of femur; sexual dimorphism of dorsal setae of femur IV and genu IV not developed (Figs 27A, 27B), although male dorsal setae ad2 and pd2 of femur with bases on a common bump-like projection (Fig. 22E). Other characteristics as in female.
Deutonymph (Figs 14C, 18A, 18B, 18D, 20G–20L, 24–26, 27C–27F). Dorsal idiosoma (Fig. 10). Idiosoma 450–550 μm long, 315–460 μm wide (n = 10), elongate, suboval, covered by two dorsal shields and with the same number of setae as in adults; in mature deutonymphs probably before molting, idiosoma conspicuously expanded laterally, subcircular, not completely covered by the shields. Podonotal shield 210–255 μm long, 245–310 μm wide, subpentagonal, with indistinct or only faintly indicated medial scleronodules between z5 and 19 pairs of setae (lacking j1, r2 and r3, located on soft integument outside shield); anterior margin straight, as if truncated, without vertical setae (j1 rarely with asymmetrical placement on shield margin) and rarely a paravertical seta (z1); bases of j1 and z1 with position on ventral side and covered by convex idiosomal vertex in freshly molted deutonymphs (Figs 26A–C). Opisthonotal shield 195–250 μm long, 240–310 μm wide, with straight anterior and well-rounded posterior margins and with similar setation as in female, except for presence of four pairs of marginal setae (R2 – R5, located on the soft integument adjacent to the lateral margins of shield). Surface of both dorsal shields similarly ornamented as in female except for reticulation in areas between setae J1–J3, Z1 and Z2, which consists mainly of dots instead of lines. Dorsal setae mostly thin and needle-like, only Z5 and S5 elongate and whip-like as in adults. Soft integument densely striated. Lengths of selected dorsal setae as follows: j1 22–27 μm, j2 22–28 μm, j3 26–34 μm, j4–j6 15–21 μm, z1 10–15 μm, z5 15–19 μm, s1 13 –18 μm, s5 30 –35 μm, s6 32 –37 μm, r2 16–21 μm, r3 34–40 μm, J1 and J2 16–21 μm, J3 and J4 13–17 μm, J5 7–12 μm, Z1 and Z2 24–31 μm, Z3 and Z4 16–21 μm, Z5 180–225 μm, S1 28 –35 μm, S2 29 –37 μm, S3 23 –28 μm, S4 20 –26 μm, S5 170–200 μm, R1 17–23 μm, R2 – R5 13–20 μm.
Ventral idiosoma (Fig. 25). Sternal shield 190–220 μm long, 75–95 μm wide (at widest part of iv2), with weakly sclerotized anteriormost part with st1 and obliquely striated presternal plates, with smooth and unevenly sclerotized surface and only two pairs of setae on lateral margins (st1, st3); sternal setae st2, st4 and st5 on soft integument adjacent to lateral and posterior margins of shield (Fig. 26D); rarely st2 asymmetrically on sternal margin or st3 asymmetrically on soft integument. Seven pairs of opisthogastric setae (Jv1–Jv3, Jv5, Zv1–Zv3), all arranged on the soft integument. Anal shield 65–95 μm long, 110–125 μm wide, semicircular, straight anteromedially, well curved laterally, strongly convex posteriorly and usually punctate on almost entire surface except anteromedial part; cribrum with a row of denticles (Figs 25, 27F). Two pairs of metapodal platelets, inner platelets minute, usually slit-shaped, and outer platelets distinct, suboval and with a vermiform appendage on anterior margin. Peritreme well developed, with only a few narrow fragments of peritrematal shield in anterior and submedial parts, not connected to podonotal shield, with anterior tip between setae z1 and s1. Lengths of selected ventrally located setae as follows: st1 35–42 μm, st2–st5 30–38 μm, ad 29–34 μm, pa 25–30 μm, Jv5 32–40 μm, and other opisthogastric setae 30–38 μm.
Gnathosoma (Figs 18A, 18B, 18D, 20G–L). Middle article of chelicerae 93–103 μm long (movable digit 31–37 μm), similar to female (Fig. 18A); movable digit usually with six teeth, but often also with five or seven teeth; fixed digit usually without 2–4 minute teeth in lateral row, as present in female. Ventral gnathosoma as in female (Figs 18B, 18D), with rostral setae of following length: h1 21–30 μm, h2 10–15 μm, h3 33–39 μm, pc 18–23 μm. Anterior margin of epistome as in Figs 20G–L, similar to that of female; some specimens with conspicuously widened central process (Fig. 20G). Other characteristics as in female.
Legs (Figs 14C, 27C–E). All legs shorter than idiosoma (Fig. 14C): legs I 350–420 μm, legs II 280–340 μm, legs III 270–340 μm, and legs IV 330–400 μm long. Setation as in adults, but some dorsal setae not as thickened, and apicoventral setae (av1 and pv1) of tarsi II–IV thin, needle-like and subapically arranged. Seta ad2 of tarsi II–IV elongate, distally attenuated, almost whip-like and erect (Figs 27C, 27E), similar to female. Dorsal and lateral setae of some leg segments of legs III and IV as in Figs 27C–E.
Type material
Holotype female: Slovakia, Little Carpathians Mountains, Lozorno Village, Lintavy Forest, deciduous forest, decaying fruiting body of Laetiporus sulphureus (Basidiomycota: Polyporales) growing on a trunk of Quercus sp. and infested by Diaperis boleti (Coleoptera, Tenebrionidae), elevation 330 m, September 10, 2024. Paratypes: two females, two males and 13 deutonymphs (six of them on D. boleti)—with the same collection data as in the holotype; one female — Biele Karpaty Mountains, Pruské Village, Babiná Forest, mixed forest, in Phaeolus schweinitzii (Basidiomycota: Polyporales) on a trunk of Pinus silvestris, elevation 270 m, August 17, 2023; eight deutonymphs— Borská Nížina Lowland, Lozorno Village, Dlhá Mláka Forest, pine forest with birch admixture, on D. boleti in Fomitopsis betulina (Basidiomycota: Polyporales) on a trunk of Betulus sp., elevation 180 m, June 21, 2023; one male — Borská Nížina Lowland, Vysoká Pri Morave Village, Horný Les Forest, hard floodplain forest, in L. sulphureus on a trunk of Cerasus avium, elevation 145 m, May 19, 2020; one male — Podunajská Rovina Flatland, Svätý Jur Town, Panónsky Háj Forest, deciduous forest, in L. sulphureus on a trunk of Quercus sp., elevation 135 m, June 12, 2023; one female, two males — Strážovské Vrchy Mountains, Podskalie Village, Veľké Skaly Mt., meadow, in fruiting body of Trametes cf. trogii on a trunk of Quercus sp., elevation 445 m, July 2, 2024; two dutonymphs— Tríbeč Mountains, Lovce Village, Pelúsok Brook Valley, deciduous forest, on D. boleti, in F. betulina on a trunk of Betulus sp., elevation 340 m, June 3, 2024. All these specimens were collected by the author and are deposited at the Institute of Zoology of the Slovak Academy of Sciences, Bratislava, Slovakia.
Etymology
The specific name of this species refers to its phoretic association with the darkling beetle of the genus Diaperis Geoffroy.
Ecological notes
The phoretic deutonymphs of Insectolaelaps diaperi are not rare in the forest areas of southwestern Slovakia, especially in some polypore fungi inhabited by their specific host beetle Diaperis boleti, such as Fomitopsis betulinus, Laetiporus sulphureus, Phaeolus schweinitzii and Trametes cf. trogii. If this beetle was missing in the examined fungus, we were also unable to detect the mite. In contrast to the tenebrionid Neomida haemorrhoidalis, D. boleti is not a monophagous fungivore and feeds on a much broader spectrum of fungal species. In general, it prefers sporocarps of various “soft” polypores growing mainly on deciduous trees. Insectolaelaps diaperi is a monoxenous species and, unlike Insectolaelaps latopini, has not been found on other fungivorous tenebrionids. The deutonymphs of I. diaperi are relatively large and can also be found on the body surface and in the subelytral cavity of adult beetles.
The beetle Diaperis boleti seems to be the main host for two mesostigmatic mites. In addition to the deutonymphs of Insectolaelaps diaperi, it also harbors the females of the fungicolous blattisociid mite Lasioseius boleti recently described by Mašán (2023a). The beetle is widespread in Slovakia and occurs in Europe, Northwest Africa and Asia (Burakowski et al. 1987). Its typical habitat is old deciduous forests, but it can also be found in fungi on isolated trees in parks or gardens. The longevity of the “soft” and “fleshy” sporocarps of the above-mentioned fungi is considerably reduced compared to perennial fungi such as Fomes fomentarius, e.g. only one year in Laetiporus sulphureus, so that some beetles (together with mites) that survive the winter have to colonize a new fungus at the beginning of the new reproductive season (Burakowski et al. 1987).
Despite the enormous effort and the high number of phoretic deutonymphs on the host beetles in the observed fruiting bodies, only a limited number of adult individuals could be obtained from the sporocarps. The adults were collected individually from both sides of the fungal surface (in the case of Laetiporus sulphureus), from tunnels left by larvae of different fungivorous insects in the fungal tissue (L. sulphureus, Phaeolus schweinitzii), and inside the pores of the active hymenophore (Trametes cf. trogii).
Taxonomic notes
With the broadened shape of the idiosoma and ventrianal shield, most of the dorsal setae of similar length and the straight anteromedial margin of the opisthonotal shield, Insectolaelaps diaperi is most similar to Insectolaelaps japanoarmatus Hirschmann & Wiśniewski, 1982, a species originally based only on barely adequate illustrations of misidentified females of Insectolaelaps armatus from Japan (Ishikawa 1980). The females of the two species can be easily distinguished by the following characters, with the corresponding data for I. diaperi in parentheses: 1) setae J4 longer than j5 and J1: J4>j5≈J1 (J4 shorter than j5 and J1: J4<j5≤J1), 2) movable cheliceral digit with eight teeth in addition to the terminal hook (with six to seven teeth), 3) bases of setae st1–st4 longitudinally aligned, all near the lateral margins of the sternal shield (st3 conspicuously adjacent and in the submedial part of the shield), and 4) ventrianal shield with straight anterior margin and widened posterior part (with widely convex anterior margin and widened anterior part).
Insectolaelaps latoarmatus Hirschmann & Wiśniewski, 1982 from North America is another very similar species, which can be distinguished from the new species by the same features as in Insectolaelaps japanoarmatus, such as the form and arrangement of the setae on the sternal shield, the shape of the ventrianal shield, the relative length of the opisthonotal setae J4 and the dentition of the movable cheliceral digit.
Among the Insectolaelaps species, deutonymphs are known in about ten species. All these deutonymphs have a normal number of four pairs of setae on the sternal shield (st1–st4). The same structure of the deutonymphs of Insectolaelaps diaperi is unusual in that it has only two pairs (st1, st3) on the lateral edges of the shield. The arrangement of the sternal setae is often related to the size of the shield, but in the new species it does not seem to be reduced compared to congeners. I am currently not aware of any digamasellid species with a similar feature.
description: Published as part of Mašán, Peter, 2025, Digamasellid mites (Acari: Mesostigmata) in association with saproxylic darkling beetles (Coleoptera: Tenebrionidae) and wood-decaying fungi (Polyporales) in Slovakia, pp. 1-58 in Zootaxa 5627 (1) on pages 9-13, DOI: 10.11646/zootaxa.5627.1.1, http://zenodo.org/record/15325037