Troglopedetes albus Joseph, 1872

Medium sized Paronellidae. Body colour white, sometimes with light orange to red pigment dots. Eyes per side 0–3. Scales present on antenna, head, body and ventral side of furca, absent on ventral tube and legs. Pseudopores on tergites arranged as 1, 1/1, 1, 1, 1 by half tergite from Th. II to Abd. IV, with a row of 4+4 pseudopores behind the posterior row of chaetae of Abd. IV. Labial basis chaetotaxy as M1M2R(r)E(e)L1(l1)L2(l2). Presence of one or two sublobal hairs on maxillary outer lobe. Antennae of various length, composed of four segments, with Ant. IV always divided into two equal or subequal sub-segments and devoid of apical bulb. Suture zone of head when visible follows divergent lines. Trichobothrial pattern 0, 0/0, 2, 3, 3. Dorsal macrochaetotaxy oligochaetotic, polychaetotic on the collar. Macrochaetae on head present as 0–7+0–7 in area dorsalis (central mac). Th. II with a compact group of 6+6 mac accompanied by 0–4+0–4 mac anteriorly. Th. III with a group of 3+3 mac accompanied by 0–1+0–1 mac anterior-externally. Claw with 0–2 inner teeth, a pair of lateral ones and a dorsal tooth. Dens elongated with one or two rows of spines, those on external row larger, more serrated than those on internal row. Mucro of various length, 2–16 × shorter than dens, with 3–5(6) main teeth, proximal tooth sometimes with 1–5 basal toothlets.

The number and arrangement of trichobothria on Abd. IV allows clear separation of Troglopedetinae (3+3 trichobothria) from other Paronellidae (2+2 trichobothria). Many characters are unknown for several species of Troglopedetes, including its type species. Two characters complementary to those listed by Soto-Adames et al. (2014) are discussed below. A new set of characters present in Troglopedetes are presented below as a result of this work.

Pseudopores are arranged on tergites as in other Entomobryoidea: 1, 1/1, 1, 1, 1 from Th. II to Abd. IV. Additionally, a row of 4+4 pseudopores is constant behind the posterior row of chaetae of Abd. IV (Deharveng, 1988a). These pseudopores are present in Cyphoderopsis (Jantarit et al. 2013) and were reported in various number (4–10+4–10) under the name “lenticular organs” sensu Christiansen and Bellinger (1996) in Trogolaphysa (Soto-Adames and Taylor 2013) and in Troglobius (Cipola et al. 2016). They have also been detected in Cyphoderidae (Jantarit et al. 2014), but not in other families of Entomobryoidea, pointing to relatedness between the cited genera and Cyphoderidae, which have led some Collembologists to consider Cyphoderidae as a subfamily of Paronellidae.

Dorsal clothing of macrochaetae is clearly oligochaetotic in the Troglopedetes species where it has been described. Pattern on Th. II includes a compact group of six chaetae (P3 complex of Soto-Adames et al. 2014) which is very obvious and constant. The same group, including 3–6 mac, is present in Trogolaphysa (Soto-Adames 2015, Soto-Adames and Taylor 2013), and a group of three or four mac in a line is found in Cyphoderopsis (Jantarit et al. 2013). The pattern on Th. III exhibits a group of three mac in Troglopedetes whereas Trogolaphysa shows 0–3 mac and Cyphoderopsis has none.

Dens of Troglopedetes is elongated with either one or two rows of spines, those of the external row larger and more serrated than those of the internal one that are rather short and smooth. Soto-Adames et al. (2014) mistakenly stated that Troglopedetes has a single row of dental spines. In fact, species of the Mediterranean region, Africa, south-west and central Asia known so far have only one row of 8–45 dental spines, but all Thai species have two rows of dental spines (internal row with 9–45 spines, external one with fewer spines).

Holotype male and seven paratypes on slides (one male, four females and two subadults). Thailand: Satun Province: La-Ngu district, Tham Kae, 6°53'41"N, 99°46'44"E, 24 m a.s.l., 25 Jul 2017, S. Jantarit, A. Nilsai and K. Surakhamhaeng leg., dark zone of cave, by aspirator (sample # THA_SJ_STN04). Holotype and five paratypes deposited in NHM-PSU, two paratypes deposited in MNHN. Measurements of holotype in Table 1.

Habitus. Slightly troglomorphic, slender, with elongate legs, furca and antennae. Body length 1.3–1.6 mm. Fourth abdominal segment 3.5–6 × (n = 9, all adults) as long as the third one along dorsal axis. Furca well developed, ca. 1.6–2.2 (n = 8) × shorter than body length. Body colour white with spots of orange pigment. Eyes absent, no ocular patch.

Chaetal types. Four types of chaetae on somites, appendages (except antennae) and mouthparts: scales, present on antennae I and II, head, body and furca, absent on legs and ventral tube; ordinary chaetae on all body parts; S-chaetae and trichobothria on tergites; hairs devoid of sockets on outer maxillary lobe and labial papilla. Chaetal types on antennae are much more diverse and described further separately.

Pseudopores (Figs 2A, 3B–D, 4B, 8A–D, 10B, 10D, E). Pseudopores present as round flat disks larger than mac sockets, on antennae, head and tergites. Dorsal pseudopore formula: 1–(2)/1, 1/1, 1, 1, 1+4 (Fig. 8A–D). On antenna, two psp detected ventro-distally on Ant. I, one ventro-distally on Ant. II and one ventro-distally on Ant. III (Figs 3B, D, 4B). On head, 1–(2) psp close to antennal basis (Fig. 2A). On legs, psp present externally on coxae (two for legs I and II and 2–(3) for leg III). On manubrium, two psp on the dorso-distal plaque (Fig. 10B, D, E), on dens (new location for Troglopedetes) two psp dorso-basally near the internal spine on each side (Fig. 10D, E).

Mouthparts. Labral formula 4/5,5,4 (Fig. 2G); prelabral chaetae short, bent and ciliated, labral chaetae thinner, longer, smooth and acuminate, those of the distal row slightly shorter than those of the median row. Ventro-distal complex of labrum well differentiated, asymmetrical, with 2 distal combs (a larger one with 6–8 teeth on the left side, a smaller one with more than ten minute teeth on the right side) and an axial pair of sinuous tubules as in Cyphoderopsis (Jantarit et al. 2013) (Fig. 2F). Distal part of labrum not adorned with spines dorso-distally. Labial palp similar to that described by Fjellberg (1999) for Troglopedetes sp., with strong papillate chaetae. Indicative number of guards for each major papillate chaetae: A (0), B (5), C (0), D (4) and E (4); lateral process subcylindrical, reaching slightly above the apex of papilla E (Fig. 2C); five smooth proximal chaetae. Chaetae of labial basis as M1M2REL1l2, with M1, M2, E and L1 subequal and ciliated, R shorter than others and ciliated, l2 short, smooth and acuminate (Fig. 2I). Outer maxillary lobe with one papillate chaeta, one basal chaeta and two sublobal hairs, shorter than others (Fig. 2B). Maxillary head with a 3-toothed claw, several stout shortly ciliated lamellae not observed in detail and three thin elongate structures (two dorsally and one ventrally) (Fig. 2D, E). Mandible head strong, asymmetrical (left side with four teeth, right side with five teeth); molar plate with three strong pointed basal teeth, and other two or three inner distal teeth, identical in both mandibles (Fig. 2H).

Ventral chaetotaxy of head (Fig. 2I). Head densely covered with oval scales (40–50 µm), postlabial chaetae along the linea ventralis as three mes anteriorly, one mac and an oblique line of five mes posteriorly on each side.

Antennae (Figs 3–7). Antennae shorter than body, 2.2 × (n = 6) as long as cephalic diagonal. Ant. IV subdivided into two subequal segments, without apical bulb (Fig. 5). Lengths of antennal segments I-IV (IVa+IVb) as 1:1.9:1.3:2.5 (average, n = 6). Two other specimens with Ant. II and III fused (Figs 6, 7). Antennal chaetae (scales, five types of ordinary chaetae, 14 types of S-chaetae and subapical organite) described separately. Antennal scales oval, present dorsally only on Ant. I and II and ventrally on Ant. II, absent ventrally on Ant. I, and absent on Ant. III and IV (Figs 3A, C, D, 6B–D).

Body dorsal chaetotaxy (Figs 2A, 8A–D). Dorsal macrochaetae formula: 4,4/8,4/0,2,4,3 (Figs 2A, 8A). Trichobothrial pattern: 1/0, 0/0, 2, 3, 3 (Figs 2A, 8A). Trichobothrial complexes well developed with modified mes of various sizes (Fig. 8A–D) described below for each segment. The figured mes pattern is not complete.

Head with 12–13 peri-antennal mac in line on each side, with 4+4 central mac (chaetae A, B, E, F of Deharveng and Gers (1993), absence of the chaetae C, D and G, cephalic mes short, feebly serrated, equal, symmetrically arranged (not analysed). One lateral cephalic trichobothrium much shorter than closest mac on each side; suture zone not visible (Fig. 2A). Head dorsally densely covered with round to oval scales (20–35 µm). Body densely covered with oval scales (15–50 µm).

Th. II with a collar consisting of a few rows of mac along its anterior and antero-lateral margins, a compact group of six central mac on each side (“P3 complex” of Soto-Adames et al. (2014) and two antero-lateral mac; one antero-lateral ms; one antero-lateral sens; two or three short mic laterally, and a few others not counted centrally (Fig. 8A).

Th. III with four mac by side (a group of three central and one anterior to them), one sens at antero-lateral margins, and ca. eight or nine mac or long mes at lateral margins (Fig. 8A).

Abd. I without central mac, with one ms laterally on each side, and three mes laterally, mic not counted (Fig. 8A).

Abd. II with two tric on each side and six or seven modified mes around them (three or four around the internal tric and three near external tric), two mac (one near internal tric and one near external tric), one sens near internal tric (Fig. 8A, B), three mic (one close to internal tric and two close to external tric), others mes sockets internally visible, not counted.

Abd. III with three tric on each side (one internal, two external) and eight or nine modified mes around tric (two near internal tric, six or seven near the two external tric); four mac (one near internal tric and three near external tric); one sens anterior to internal tric and one ms posterior to the two external tric; several mes at lateral margins, not counted (Fig. 8A, C).

Abd. IV with three tric on each side (two antero-lateral, one postero-lateral) and ca. 7–9 modified mes around the two antero-lateral tric; postero-lateral tric without modified mes. Mac distributed as three central on each side (one antero-external to pseudopore, two anterior to posterior tergite margin), one near postero-lateral tric, and at least four external, mixed with many mes or smaller mac on lateral to posterior margins (not counted); probably three sens anteriorly; at least six S-like chaetae sensu Lukić et al. (2015) anteriorly, and several mes or S-like chaetae uniformly distributed (not counted); six serrated mes in line in the posterior row, four near axis and two along pseudopore line, from medium to short size (Fig. 8A, D).

Abd. V with only one sens detected on each side, and several ordinary chaetae from mes to mac, not counted (Fig. 8A). Abd. VI chaetotaxy not analysed.

Legs (Fig. 9A–C). Legs long. Tita III as long as head diagonal, slightly longer than Tita I and II. Legs devoid of scales, mostly covered with ordinary ciliated chaetae of various length, from mes to mac. Trochanteral organ of leg III with eight smooth, straight, unequal, spiny chaetae (n = 1) (Fig. 9C). Tibiotarsus chaetotaxy mostly composed of strong ciliated-serrated mes, the basal ones longer and thicker (50–60 µm), slightly shorter distally (up to 15–20 µm). Distal row with 8–10 subequal ciliated mes and a dorso-apical tenent hair thin, smooth and acuminate on all tita; a ventro-distal strong smooth erected chaeta present on Tita III (Fig. 9A). Praetarsal mic minute (2.5–3 µm) (Fig. 9A). Unguis slender and relatively short (25–30 µm long, 6–7 µm wide at basis), 8–9 × shorter than tita, with one rather strong tooth at 30% of inner edge and a pair of inner basal teeth of unequal size; unguiculus pointed, narrow, lanceolate and elongate, ca. 0.6 × as long as claw, its external edge smooth (Fig. 9A).

Ventral tube (Fig. 9D–F). Ventral tube ca. 4 × longer than wide, with 3+3 long serrated mac anteriorly (Fig. 9D) and six mes (two ciliated and four smooth) on each lateral flap (Fig. 9E); posteriorly with at least 31 long ciliated mes and two distal smooth mes (Fig. 9F).

Furcal complex (Fig. 10A–E). Tenaculum with four teeth on each ramus, of decreasing size from the basal to the distal one, on a prominent, irregular body, with a postero-basal strong, densely serrated, distally bent chaeta (Fig. 10A). Manubrium ca. 0.82 × (n = 8) shorter than mucrodens (mucro+dens). Manubrium dorsally with subequal ciliated mes (none smooth), irregularly arranged in three or four rows in two longitudinal stripes separated by a glabrous axial stripe, external row of chaetae distally with at least 7–11 long ciliated mes, dorso-distal plaque with 4+4 mes and 2+2 pseudopores (Fig. 10B). Ventrally, dense cover of round to oval (22–38 µm) and thin elongated scales (20–25 µm). Dens straight, elongate, hairy, slightly and progressively tapering, dorsally with two rows of spines, mixed with ciliated mes of various length, thickness and shape. Dorso-external row with 15–22 spines, dorso-internal row with 26–40 spines (asymmetries between dentes); external spines larger and less sclerotised than internal ones. Some short ciliated mes interspersed with spines in the external row; dorsally between the two rows of spines a mix of short and long ciliated mes, irregularly arranged in one row distally turning to three or four rows proximally; laterally, many short ciliated mes; dorso-distally, 3–(4) stronger ciliated mes; 2+2 psp on dorso-basally between the two rows of spine, sometimes inconspicuous (Fig. 10C, D). Dens ventrally entirely and densely scaled, the scales elongate (20–38 µm) (oval shape distally), arranged in short lines from 3–5 (distally) to 6–8 scales (proximally) (Fig. 10D). Mucro rather stout, short, 9.3–13.7 (average 12, n = 8) × shorter than dens (Fig. 10D, E), with five main teeth, the apical one blunt and strong, the subapical one acute and strong, a latero-distal one small and acute, and two dorso-basal, one minute and acute and one strong, acute and longer without toothlets basally (Fig. 10E).

Genital plate (Fig. 10F, G). Male genital plate of the circinate type, with six genital mic and 16 circumgenital short, thin, smooth mes (Fig. 10F); female genital plate with 2+2 mic (Fig. 10G).

Troglopedetes kae sp. nov. is only known from a small chamber in the dark zone of a cave, accessible by a very low and narrow passage. Specimens were found as small populations in an oligotrophic habitat, i.e., on wall and ground with very humid and wet environment, without any trace of organic matter.

The species name is taken from the type locality (Tham Kae).

Troglopedetes kae sp. nov. has four medial head macrochaetae, three medial Abd. IV macrochaetae, one inner teeth of claw and mucro with five teeth. It is near T. centralis Deharveng & Gers, 1993 from a cave in Doi Chiang Dao, Chiang Mai province in the absence of eyes, chaetotaxy of labial basis and of outer maxillary lobe, dorsal macrochaetotaxy from head to Abd. IV, chaetotaxy of anterior side of ventral tube and claw morphology. However, T. kae sp. nov. differs from T. centralis by its smaller size (1.3–1.6 vs. 1.7–2.1 mm), body colour with spots of orange pigment (vs. white), longer antennae (0.5–0.6 × as long as body vs. 0.4), thinner claw with an internal tooth at 30 vs. 50–65% from the basis, chaetae on lateral flap of the ventral tube (6+6 vs. 7+7), higher ratio dens:mucro (9.3–13.7 vs. 8.8), and mucro with five teeth (vs. four).

In the same cave and same habitat, we found another morphotype with very different claw complex; thick and clavate tenent hair, two strong inner teeth on claw at 74% and 91% of inner edge, and external edge of unguiculus with two or three minute outer basal teeth, sometimes inconspicuous (Fig. 9B). However, material was not enough to describe it in detail.

The locality where T. kae sp. nov. was collected is located 400 km south of the Isthmus of Kra, i.e., more south than other described Troglopedetes from Thailand. The Isthmus of Kra is well-known to be a biogeographical transition zone between Indochinese and Sundaic fauna (Fig. 1). It was previously considered to be the southern distribution limit for the genus Troglopedetes, and the northern limit for the closely related genus Cyphoderopsis in Thailand (Deharveng and Gers 1993, Jantarit et al. 2013). This discovery provides evidence that the two genera may actually overlap in southern Thailand, and questions the role of the Isthmus of Kra as biogeographical barrier for cave fauna.

Holotype male and four paratypes (one female, three subadults) on slides. Thailand: Chumphon Province: Lang Suan district, Tham Don Non (Tapan), 9°54'14"N, 99°02'41"E, ca 60 m a.s.l., 25 Jul. 2015, S. Jantarit leg., dark zone of cave, by aspirator (sample # THA_SJ_CPN01). Holotype and two paratypes deposited in NHM-PSU. Two paratypes deposited in MNHN. Measurements of holotype in Table 2.

Habitus. Slightly troglomorphic, slender, with elongate legs, furca and antennae (Figs 1, 11A). Body length 1.3–1.5 mm. Fourth abdominal segment 3 × as long as the third one along dorsal axis. Furca well developed, ca. 2 × shorter than body length. Body colour white with spots of orange pigment. Eyes absent, no ocular patch.

Chaetal types. Four types of chaetae on somites, appendages (except antennae) and mouthparts: scales, present on antennae I and II, head, body and furca, absent on legs and ventral tube; ordinary chaetae on all body parts; S-chaetae and trichobothria on tergites; hairs devoid of sockets on outer maxillary lobe. Chaetal types on antennae are much more diverse and described separately further.

Pseudopores (Figs 12C, 13D, 15A, B, D). Pseudopores present as round flat disks larger than mac sockets, on antennae, head and tergites. Dorsal pseudopore formula: 1–(2)/1, 1/1, 1, 1, 1+4 (Figs 11J, 15A). On antenna, 1–(2) psp detected ventro-distally on Ant. I., one ventro-distally on Ant. II and one ventro-distally on Ant. III, sometimes not clearly seen (Figs 12C, 13D). On head, 1–(2) psp close to antennal basis. On legs, psp present externally on coxae (two for legs I and II and 2–(3) for leg III). On manubrium, two psp on each dorso-distal plaque, on dens (new location for Troglopedetes) two psp dorso-basally near the internal spine on each side (Fig. 16E).

Mouthparts. Labral formula 4/5,5,4; prelabral chaetae short, bent and ciliated, labral chaetae thinner, smooth and acuminate, those of the distal row slightly shorter than those of the median row. Ventro-distal complex of labrum well differentiated, asymmetrical, with two distal combs (a larger one with 6–8 teeth on the left side, a smaller one with more than ten minute teeth on the right side) and an axial pair of sinuous tubules. Distal part of labrum not adorned with spines dorso-distally. Labial palp similar to that of T. kae sp. nov. (Fig. 11B). Chaetae of labial basis as M1M2REL1l2. Chaetae M1, M2, E and L1 subequal and ciliated, R shorter than others and ciliated, l2 short, smooth and acuminate (Fig. 11D, G). Outer maxillary lobe with one papillate chaeta, one basal chaeta and two sublobal hairs, shorter than others (Fig. 11C). Maxillary head with a 3-toothed claw, several stout shortly ciliated lamellae not detailed here; special structures present on the maxilla head, i.e., a thin elongate structure, arising from the basis of the maxilla head and reaching claw basis; close to it a spiny structure and a thin structure in an opposite side (Fig. 11F). Mandible heads strong, asymmetrical (left side with four teeth, right side with five teeth); molar plate with three strong pointed basal teeth, and other two or three inner distal teeth, identical in both mandibles (Fig. 11E).

Ventral chaetotaxy of head (Fig. 11D, G). Head densely covered with oval scales (40–50 µm), postlabial chaetae along the linea ventralis as three mes anteriorly, one mac and one oblique line of four or five mes posteriorly on each side.

Antennae (Figs 11H–I, 12A–D, 13A–F, 14A–C). Antennae shorter than body, ca. 2 × (n = 3) as long as cephalic diagonal. Ant. IV subdivided into two subequal segments, without apical bulb. Lengths of antennal segments I to (IVa+IVb) as 1:1.8:1.5:2.9 (average, n = 3). Antennal chaetae (scales, five types of ordinary chaetae, 13 types of S-chaetae and subapical organite) described separately. Antennal scales oval, present dorsally only on Ant. I and II and ventrally on Ant. II, absent ventrally on Ant. I, and absent on Ant. III and IV (Figs 11H, 12A–D, 13D–F).

Dorsal chaetotaxy (Figs 11J, 15A, B, D). Dorsal macrochaetae formula: 1,4/8,4/0,2,4,3 (Figs 11J, 15A). Trichobothrial pattern: 1/0, 0/0, 2, 3, 3 (Figs 11J, 15A, B, D). Trichobothrial complexes well developed with modified mes of various sizes (Fig. 15A–D) as described below for each segment. The mes pattern is not complete. Head with 12 or 13 peri-antennal mac in line on each side; with 1+1 central mac (chaetae A of Deharveng and Gers 1993), chaetae B-F absent, at least 9+9 cephalic mes short, feebly serrated, equal in size, symmetrically arranged (Fig. 11J). One lateral cephalic trichobothria much shorter than closest mac on each side; suture zone visible, without associated mac (Fig. 11J). Head dorsally densely covered with round to oval scales (20–35 µm). Body densely covered with oval scales (15–50 µm).

Th. II collar consisting of a few rows of mac along its anterior and antero-lateral margins, a compact group of six central mac on each side (“P3 complex”) and two antero-lateral mac; one antero-lateral ms; one antero-lateral sens; two or three short mic laterally, and a few others not counted centrally (Fig. 15A).

Th. III with four mac on each side (a group of three central and one anterior to them); one sens at antero-lateral margins; one mic laterally; and ca. 11+11 mac or long mes at lateral margins (Fig. 15A).

Abd. I without central mac, with one ms laterally on each side; two or three mic arranged in line externally to pseudopore and two larger lateral mic; three mes laterally (Fig. 15A).

Abd. II with two tric on each side and six or seven modified mes around them (two around the internal tric and four or five near external tric), two mac (one near internal tric and one near external tric), one sens near internal tric; three mic (one close to internal tric and two close to external tric), others mes sockets internally visible, not counted (Fig. 15A, B).

Abd. III with three tric on each side (one internal, two external) and nine or ten modified mes around tric (two near internal tric and seven or eight near the two external tric); four mac (one near internal tric and three near external tric); one sens anterior to internal tric and one ms posterior to the two external tric; two mic/mes external to the external mac; several mes at lateral margins, not counted (Fig. 15A, C).

Abd. IV with three tric on each side (two antero-lateral, one postero-lateral); and ca. 6–9 modified mes around the two antero-lateral tric; postero-lateral tric without modified mes. Mac distributed as three central on each side (one antero-external to pseudopore, two anterior to posterior tergite margin), one near postero-lateral tric, and four or five external, mixed with many mes or smaller mac on lateral to posterior margins (not counted); probably three sens anteriorly; at least seven S-like chaetae sensu Lukić et al. (2015), and several mes or S-like chaetae uniformly distributed (not counted); six serrated mes in line in the posterior row (one near axis and five along pseudopore line, from medium to short) (Fig. 15A, D).

Abd. V with only two sens detected on each side, and several ordinary chaetae from mes to mac in size (Fig. 15A). Abd. VI chaetotaxy not analysed.

Legs (Fig. 16A, B). Legs long; Tita III as long as head diagonal, slightly longer than Tita I and II. Legs devoid of scales, mostly covered with ordinary ciliated chaetae of various length, from mes to mac. Trochanteral organ of leg III with 11–13 smooth, straight, unequal spiny chaetae (Fig. 16B). Tibiotarsus chaetotaxy mostly composed of strong ciliated-serrated mes, basal ones longer and thicker (60 µm), the distal ones slightly shorter (up to 15–20 µm). Distal row with ten subequal ciliated mes and a dorso-apical tenent hair thin, smooth and acuminate on all tita; a ventro-distal strong smooth erected chaeta present on Tita III (Fig. 16A). Praetarsal mic minute (2.5–3 µm, Fig. 16A). Unguis slender and relatively short (27–30 µm long, 6–7 µm wide at basis), 8–9 × shorter than tita; with one rather strong tooth at 50–55% of inner edge and a pair of inner basal teeth of unequal size (Fig. 16A). Unguiculus acuminate, 0.6 × as long as claw, its external edge with a minute outer basal tooth, sometimes inconspicuous (Fig. 16A).

Ventral tube (Fig. 16C). Ventral tube 4 × longer than wide; with 3+3 long serrated mac anteriorly and six mes (two ciliated and four smooth) on each lateral flap (Fig. 16C); posteriorly with many long ciliated mes, not suitable for observation in available specimens.

Furcal complex (Fig. 16D–F). Tenaculum with four large teeth on each ramus, of decreasing size from the basal to the distal one, on a prominent, irregular body, with a postero-basal strong, densely serrated, distally bent chaeta (Fig. 16D). Manubrium slightly shorter than mucrodens (ca. 0.95 ×). Manubrium dorsally with subequal ciliated mes (none smooth) irregularly arranged in 3–4 rows in two longitudinal stripes separated by a glabrous axial stripe, external row of chaetae distally with at least 5–7 long ciliated mes, dorso-distal plaque with 4+4 mes and 2+2 pseudopores. Ventrally, dense cover of round to oval (20–38 µm) and thin elongated scales (20–25 µm).

Dens straight, elongate, hairy, slightly and progressively tapering, dorsally with two rows of spines, mixed with ciliated mes of various length, thickness and shape. Dorso-external row with 17–20 subequal spines, dorso-internal row with 30–37 subequal spines (asymmetries between dentes); external spines larger and less sclerotised than internal ones. Short ciliated mes interspersed with spines in the external row; dorsally between the two rows of spines a mix of short and long ciliated mes, irregularly arranged in one row distally turning to 3–4 rows proximally; laterally, many short ciliated mes; dorso-distally, 3–(4) stronger ciliated mes; 2+2 psp on dorso-basally between the two rows of spine, sometimes inconspicuous. Dens ventrally entirely and densely scaled, scales elongate (20–38 µm), arranged in short lines from 3–5 (distally) to 6–8 scales (proximally) (Fig. 16E).

Mucro rather stout, short, 12–15 × shorter than dens (Fig. 16E, F), with four main teeth, the apical one blunt and strong, the two subapical ones smaller, the dorso-basal one slightly longer with one or two toothlets basally (Fig. 16F).

Genital plate. Genital plate not seen.

Troglopedetes meridionalis sp. nov. was found in small populations in the dark zone of a cave, foraging on a small patch of old and humid bat guano.

The name of the species, meridionalis, means southern in Latin, referring to the location of the species in the southern part of peninsular Thailand.

Troglopedetes meridionalis sp. nov. is the only species of the genus with one medial head macrochaeta. It is similar to T. convergens Deharveng & Gers, 1993 from a cave of Ratchaburi province in the absence of eyes, two rows of dental spines, labial basis chaetotaxy, similar dorsal chaetotaxy from head to Abd. IV, anterior ventral tube chaetotaxy, and claw morphology. It can be distinguished by the combination of characters listed in Tables 3A and 3B, in particular the absence of the chaetae “E” on head, larger size (1.3–1.5 vs. 0.95–1.3 mm), antennae relatively shorter (0.35–0.4 vs. 0.45–0.5 × as long as body), tenent hair acuminate vs. usually clavate, each lateral flap of ventral tube with six chaetae (vs. seven), dental spines of the internal row more numerous (30–37 vs. 19–23) and higher ratio of dens:mucro (12–15 vs. 9).

The pair of mac immediately ahead A and that ahead the uneven anterior mac on head are not figured in Deharveng and Gers (1993), as they were not considered as mac, but long mes. Their sockets in the new species are smaller than those of mac, but clearly marked.