Holotype : female on slide. Thailand, Khon Kaen province, Chum Phae district, Tham Nayn Noi (note: “tham” = “cave” in Thai), altitude 359 m a.m.s.l., 16.8292°N, 101.9848°E. 3.XII.2020; S. Jantarit, A. Nilsai, K. Sarakhamhaeng and K. Jantapaso leg. (sample # THA_SJ_KKN04), dark zone of a cave, by entomological aspirator. Paratypes: same data as holotype, 11 specimens (three female and eight subadults on slides). Additional material: same data as holotype, 3 specimens (in ethanol)

Holotype and 11 paratypes on slides deposited in NHM-PSU.

Habitus (Fig. 1A). Medium size Entomobryidae. Body length 1.8–2.3 mm (holotype 1.8 mm). No scales. Eyes absent. Color: whitish in alcohol, without pigmentation. Four antennal segments. Body slender not bent nor humped at the level of Th. II. Abd. IV 3.80–5.63 times as long as Abd. III along the dorsal midline.

Pseudopores (Figs 3F, 4A–C). Pseudopores present as round flat disks, smaller than mac sockets, except for the coxae and manubrium where psp are as large as mac sockets, present on various parts of the body: antennae, head, tergites, coxae and manubrium. On antennae, psp located ventro-apically between the tip of antennal segments and the chaetae of the apical row, or just below the apical row of chaetae (2 psp on Ant. I, 2–3 psp on Ant. II, and 3 psp on Ant. III). On the head, 1–2 psp located externally on each peri-antennal area. On tergites, 1+1 psp close to the axis from Th. II to Abd. IV (Figs 4A–C). On coxae, 1–2 psp on coxae I, 2–3 psp on coxae II and 1–2 psp on coxae III, located close to longitudinal rows of chaetae. On manubrium, 2+2 dorso-apical ones (Fig. 3F).

Clypeus and mouthparts (Figs 2A–C, 2H, I, 3G). Clypeal area with three long, smooth prefrontal; six middle chaetae (2+2 small ciliated chaetae of unequal size posteriorly and 1+1 rather long, thin, smooth chaetae anteriorly); and 1+1 long smooth lateral chaetae (Fig. 3G). Prelabral and labral chaetae 4/5, 5, 4, all thin and smooth; the three median chaetae of the second row longer than two lateral ones (35–40 vs. 25 µm) (Fig. 2H). Distal border of the apical non-granulated area of the labrum with a relatively narrow median U- or V-form intrusion into the granulated area dorsally; apical edge without spines (Fig. 2H). Ventro-distal complex of labrum well differentiated, asymmetrical, with 1+1 distal combs of 14–19 minute teeth on the right side and 14–16 strong and larger teeth on the left side (Fig. 2A), and an axial pair of long sinuous tubules. Maxillary outer lobe with one basal chaeta, one apical chaeta (basal chaeta thicker than apical one) and three smooth sublobal hairs (55–60 vs. 35–38 µm) (Fig. 2B). Labial palp strongly modified for the genus, with 0, 5, 0, 4, 4 guards for papillae A–E, as described by Fjellberg (1999) for Entomobryidae or by Xu and Zhang (2015) and Jantarit et al. (2019) for Coecobrya. Lateral process of labial palp subcylindrical, as thick as normal chaetae, with tip beyond the apex of the labial papilla (Fig. 2C). Mandible apex blunt and strong, asymmetrical (left with four teeth, right with five teeth) (Fig. 2I); molar plate with three strong pointed basal teeth, and 3–(5) smaller inner distal teeth, identical in both mandibles. Maxilla capitulum with a three-toothed claw and several stout ciliated lamellae; lamella 2 large and broad, lamella 3 well developed; several other lamellae present as figured in Jantarit et al. (2019).

Antennae (Fig. 2D). Antennae very long, approximately 3.78–5.14 times as long as cephalic diagonal. Antennal segments ratio as I: II: III: IV. 1: 2.08–2.20: 2.17–2.21: 3.75–4.40 (N = 3). Antennal segments not subdivided nor annulated. Antennal chaetal types not analysed in detail. Ant. I ventrally with many smooth spiny mic of various sizes in its basal part, many subcylindrical, hyaline sens in its middle to apical part, and many long smooth straight chaetae. The paddle-like chaetae (sensu Nilsai et al. 2017) on Ant II dorsally absent. Ant. III organ with typical five sens, sens one and four subequal, hyaline; sens five acuminate, and shorter; sens two and three swollen in paddle-like chaetae shape (Fig. 2D). Ant. IV without apical bulb. Subapical organite not distinctly knobbed, swollen, slightly enlarged apically, inserted dorsally.

Dorsal head chaetotaxy (Fig. 3D). Dorsal cephalic chaetotaxy with four antennal chaetae (An3a2 and An3 as mac, An1–2 as mes), four anterior mac (A0, A2–3 and A5), three median (M1, M2 and M4) and eight sutural (S) mac (S0, S1–7); Gr. II with four mac; A₀ as mac; 5–7+5–7 scale-like structures (usually 6+6) (sensu Jantarit et al. 2019) present below sutural mac, probably inside the integument; a pair of short cephalic trichobothria, external and close to the middle of the head (Fig. 3D).

Ventral head chaetotaxy (Fig. 2E). Chaetae of labial basis all smooth (mrel₁l₂), chaetae m e and l₁ subequal, r thin and shortest, and l₂ longest. The r/m length ratio: 0.13–0.14 (Fig. 2E). Postlabial chaetae X₂, X and X₄ smooth, acuminate and minute chaetae, of similar size, X₃ normally absent but present as mic in one individual. On each side of the cephalic groove with 9 chaetae, of which, the proximal six always long and smooth, 7^th and 9^th as mics, 8^th always long and ciliated, one specimen with three mics distally (Fig. 2E).

Tergite chaetotaxy (Figs 4A–D). Th. II with two (m1, m2) medio-medial, one (m4) medio-sublateral and 18–20 posterior mac; 1+1 ms and 2+2 sens antero-laterally (Fig. 4A).

Th. III with 23–26 mac. 2+2 sens laterally (Fig. 4A).

Abd. I with six central mac (m4i, m2–4, m2i, m4p), 1+1 ms and 1+1 sens laterally (Fig. 4B).

Abd. II with two (m3, m3e) central and one (m5) lateral mac, 2+2 tric without modified chaetae, 1+1 sens laterally and 1+1 mic near internal tric (Fig. 4B).

Abd. III with one (m3) central and three (am6, pm6, p6) lateral mac. 3+3 tric without modified chaetae, 1+1 sens laterally, 1+1 mic near m3, ms not seen (Fig. 4B).

Abd. IV with four central mac (M, A5–6, B5) and six (D3, E2–4, E2p, F3) lateral mac, 2+2 tric and about 19 long S-like chaetae and one mic in the middle below psp, without modified chaetae (Fig. 4C).

Abd. V with at least 6 obvious mac and several mes to small mac, and 3+3 sens (Fig. 4D).

Abd. VI not analysed.

S-chaetae formula from Th. II to Abd. V: 2+ms, 2/1+ms, 2, 2, ≈ 20, 3; ps not seen, as sens on Abd. IV 1/3 as long as S-like chaetae (Figs 4A–D).

Legs (Figs 2G, 3B). Leg long; tita of leg III slightly longer than tita of legs I and II. Legs devoid of scales, covered with ordinary ciliated chaetae of various lengths, mic not seen. Trochanteral organ with 18–21 smooth, straight, unequal spine-like chaetae (Fig. 3B). The distal whorl of tita III with 10 subequal ciliated mes, irregularly arranged, and usually claw I–II with dorso-apical clavate tenent hair (pointed in two specimens). A smooth, thin and long chaeta close to tenent hair (sensu Jantarit et al. 2019) absent. Claw III generally with dorso-apical clavate tenent hair (8 individuals with clavate tenant hair, 4 individuals with pointed tenant hair; holotype with pointed tenent hair Fig. 2G). Ventro-distal smooth chaeta of tita III thick, erected, pointed, rather short. Pretarsal mic minute (2.5–3.0 µm). Claw slender and elongated. Unguis of all claw with one small inner teeth at 53 % and a pair of unequal basal teeth at about 44–49 % of inner edge from basis. Unguiculus approximately 2/3 as long as inner edge of claw, rather swollen baso-externally, pointed apically, devoid of inner tooth, with at least five minute outer teeth, often inconspicuous, at 3/4 of its length (Fig. 2G).

Ventral tube (Figs 3C, E). Ventral tube two to three times longer than wide. Lateral flaps with 6–7+6–7 smooth chaetae except for one specimen with one ciliated chaeta present in both sides (Fig. 3C). Anterior face with 6–8+6–8 chaetae, 2(3) of them larger than others, all ciliated, arranged roughly asymmetrically (Fig. 3E); posterior face with at least 12 chaetae, four apical chaetae longer and larger than others and about 8–13 proximal chaetae; two straight smooth chaetae and 6–11 either small finely ciliated or mics arranged asymmetrically (Fig. 3C).

Furcal complex (Figs 2F, 3A, F). Tenaculum with four large teeth of decreasing size from the basal to the distal one of each ramus, on a prominent, irregular body, with a postero-basal strong serrated chaeta bent distally. Mucrodens 1.6 times longer than manubrium. Furcula without smooth chaetae. Manubrium with a dense cover of ciliated chaetae both dorsally and ventrally. Manubrial plaque with 2+2 psp and three to six ciliated chaetae (usually 5+5) (Fig. 3F). Distal part of manubrium ventrally with 13+13 ciliate chaetae (Fig. 3A). Dens without spines, annulated and covered with ciliated chaetae on both sides. Distal smooth part of dens slightly longer than mucro. Mucro strong and falcate, basal spine long, reaching the tip of the mucronal tooth (Fig. 2F).

Genital plate. Female genital plate with 2+2 genital mic, male genital plate not clearly seen.

Coecobrya whitteni sp. nov. was found in the dark zone of a cave on the surface of the muddy ground, near the bank of a stream. It was also found in the upper levels on stalagmites, clay, gravel and rock surfaces. This species was found mainly in eutrophic habitats where piles of guano were well-presented. There was a big colony of the intermediate roundleaf bat (Hipposideros larvatus) inside the cave. The air temperature of the habitat where this species was collected was 22.9–24.0 °C and the relative humidity was 85%. In the same cave, and in the same chamber, at least six different stygobitic species were also observed in the small puddles: Aequigidiella aquilifera, Dugesia deharvengi, Heterochaetella glandularis, Siamoporus deharvengi, Stenasellus rigali and Theosbaena cambodjiana. The co-occurrence of these six species was first observed in 1987 (Association Pyrénéenne de Spéléologie 1988; Deharveng and Bedos 2000, 2012) and from our observations they are all still present in rather large numbers of individuals. We also found a millipede (Plusioglyphiulus saksit) and a spider (Speocera deharvengi) in the same habitat where this new species was found. Most of these observed species only known as endemics to this cave. The discovery of this new species in Tham Nayn Noi emphasizes the importance of this cave in harboring the endemic subterranean fauna of the area.

Coecobrya whitteni sp. nov. is named in honor of the late Tony Whitten in appreciation of his enormous contributions to the discovery and conservation of karst and cave invertebrates across Asia.

Among the described troglomorphic Coecobrya species in Thailand, Coecobrya whitteni sp. nov. is near to C. cavicta Nilsai & Zhang, 2017 from Satun province, southern Thailand in the body length, dorsal head chaetotaxy, labial chaetae, number of sublobal hairs on maxillary outer lobe, number of mac on Abd.III and number of chaetae on ventrodistal part of manubrium. However, it differs from C. cavicta by the combination of various characters i.e. longer length of antennae, number of mac of dorsal tergits on Th. II (21–23 vs. 36–37), Th. III (23–26 vs. 35), Abd. II (2 vs. 3) and Abd. IV (11 vs. 18–20), number of inner teeth of claw (3 vs. 2) and number of smooth chaetae of trochanteral organe (18–21 vs. 15–16) (see Table 1). In fact, Coecobrya whitteni sp. nov. is most similar to C. troglobia sp. nov. which is described in this work since the caves where these two species are found are only 3.4 km apart in a straight line, separated by limestone mountains. The altitudes of the two caves differs by about 200 m. The two species are similar in body size, antennal length, number of sublobal hair on the maxillary outer lobe, number of chaetae on Gr. II, labial chaetae, number of mac on Abd. I–IV, number of inner teeth of the claw, tenent hair, similar number in ventral tube chaetae both anterior and posterior side as well as a lateral flap, number of chaetae on trochanteral organ (Table 1). However, Coecobrya whitteni sp. nov. differs from C. troglobia sp. nov. by the number of An dorsal mac on the head (4 vs. 5) and number of chaetae on Th. II (medio-medial mac = 2 vs. 3, medio-sublateral mac = 1 vs. 4) (Table 1). Coecobrya whitteni sp. nov. has in fact already been mentioned by Deharveng and Bedos (2000) as an undescribed cf. Coecobrya species (Fig. 31.8A page 625) from oligotrophic habitats. (Note that in this reference the cave is misnamed as Tham Kubio).

Holotype : female on slide. Thailand, Khon Kaen province, Chum Phae district, Tham Phaya Nakharat, altitude 562 m a.m.s.l., 16°48'50.5"N, 101°57'23.9"E. 3.XII.2020; S. Jantarit, A. Nilsai, K. Sarakhamhaeng and K. Jantapaso leg. (sample # THA_SJ_KKN03), dark zone of a cave, by entomological aspirator. Paratypes: same data as holotype, 7 specimens (3 females and 4 subadults on slides). Additional material: same data as holotype, 6 specimens (in ethanol).

Holotype and seven paratypes on slides deposited in NHM-PSU.

Habitus (Fig. 1B). Medium size Entomobryidae. Body length 2.0–2.4 mm (holotype 2.4 mm). No scales. Eyes absent. Color: whitish in alcohol, without pigmentation. Four antennal segments (sometimes Ant. II and III fused together). Body slender not bent nor humped at the level of Th. II., elongated antennae, legs and furca. Th. II slightly larger than Th. III; Abd. IV about 3.5 times as long as Abd. III along the dorsal midline.

Pseudopores (Figs 6D, 7A–C). Pseudopores present as round flat disks, smaller than mac sockets (Figs 7A–C), except for the coxae and manubrium where psp are as large as mac sockets, present on various parts of the body: antennae, head, tergites, coxae and manubrium. On antennae, psp located ventro-apically between the tip of antennal segments and the chaetae of the apical row, or just below apical row of chaetae (2 psp on Ant. I, 2–3 psp on Ant. II, and 3 psp on Ant. III). On head, 1–2 psp located externally on each peri-antennal area. On tergites, 1+1 psp close to the axis from Th. II to Abd. IV (Figs 7A–C). On coxae, 1–2 psp on coxae I, 2–3 psp on coxae II and 1–2 psp on coxae III, located close to longitudinal rows of chaetae. On manubrium, 2+2 dorso-apical ones (Fig. 6D).

Clypeus and mouthparts (Figs 5A, B, D, G, H, 6H). Clypeal area with nine chaetae arranged in three rows, three long smooth prefrontal, 2+2 small ciliated chaetae sometimes asymmetric arrangement, and 1+1 long smooth facial chaetae, the lateral long smooth chaetae not seen (Fig. 5H). Prelabral and labral chaetae 4/5, 5, 4, all thin and smooth; three median chaetae of the second rows longer and slightly larger than those of the distal and proximal rows and longer than lateral ones (35–40 vs. 25–30 µm) (Fig. 5A). Distal border of the apical non-granulated area of the labrum with a relatively narrow median U- or V-form intrusion into the granulated area dorsally; apical edge without spines (Fig. 5A). Ventro-distal complex of labrum well differentiated, asymmetrical, with 1+1 distal combs of 14–16 minute on the right side and 14–16 strong and larger teeth on the left side (Fig. 5B), and an axial pair of long sinuous tubules. Maxillary outer lobe with one basal chaeta, one apical chaeta (basal chaeta thicker than apical one) and three smooth sublobal hairs (60–65 vs. 35–38 µm) (Fig. 5D). Labial palp strongly modified for the genus, with 0, 5, 0, 4, 4 guards for papillae A–E. Lateral process of labial palp subcylindrical, as thick as normal chaetae with tip beyond the apex of the labial papilla (Fig. 5G). Mandible apex strong, asymmetrical (left with four teeth, right with five teeth) (Fig. 6H); molar plate with three strong pointed basal teeth, and 3–(5) smaller inner distal teeth, identical in both mandibles. Maxilla capitulum with a three-toothed claw and several stout ciliated lamellae; lamella 2 large and broad, lamella 3 well developed; several other lamellae present.

Antennae (Figs 5C, E). Antennae very long, approximately 4.0–6.8 times as long as cephalic diagonal. Antennal segments ratio as I: II: III: IV = 1: 1.1–2.7: 0.7–2.4: 2.1–4.6 (N = 5). Antennal segments not subdivided nor annulated. Antennal chaetal types not analysed in detail. Smooth spiny mic at base of antennae: 3 dorsal, 3 ventral on Ant. I, 1 internal, 1 external and 1 ventral on Ant. II, 1 smooth ventral on Ant. I, smooth straight long chaetae on antennae present. Ant. I ventrally with many smooth spiny mic of various sizes in its basal part, many subcylindrical, hyaline sens in its middle to apical part, and many long smooth straight chaetae. The paddle-like chaetae on Ant II absent. Ant. III organ with five sens; sens one and four subequal, hyaline; sens five acuminate, dark and shorter; sens two and three swollen (Fig. 5C). Ant. IV very long, not subdivided, without apical bulb. Subapical organite not distinctly knobbed, swollen, slightly enlarged apically, inserted dorsally (Fig. 5E).

Dorsal head chaetotaxy (Fig. 6I). Dorsal cephalic chaetotaxy with five antennal chaetae (An1–3, An3a, An3a2, An1 as mes), four anterior mac (A0, A2–3 and A5) three median (M1–2, M4) and eight sutural mac (S0, S1–7); Gr. II with four mac; A₀ as mac; 6+6 scale-like structures present below sutural mac, probably inside the integument; a pair of short cephalic trichobothria, external and close to the middle of the head (Fig. 6I).

Ventral head chaetotaxy (Fig. 5F). Chaetae of labial basis all smooth (mrel₁l₂), chaetae m, e and l₁ subequal, r thin and shortest, and l₂ longest, The r/m length ratio: 0.11–0.16 (Fig. 5F). Postlabial chaetae X₂, X and X₄ smooth and minute chaetae, X₁ and X₃ absent. On each side of cephalic groove with 9 chaetae, of which the anterior six always long and smooth, 7^thand 9^th as mics, 8^th always long and ciliated, one specimen with three mics distally in one side (Fig. 5F).

Tergite chaetotaxy (Figs 7A–D). Th. II with three (m1, m2, m2i2) medio-medial, two (m4, m4p) medio-sublateral and 15–18 posterior mac; 1+1 ms and 2+2 sens antero-laterally (Fig. 7A).

Th. III with 24–27 mac, a4i and a6i as mac, 2+2 sens laterally (Fig. 7A).

Abd. I with six (m2–4, m2i, m4p, m4i) mac, 1+1 ms and 1+1 sens laterally (Fig. 7B).

Abd. II with two (m3, m3e) central and one (m5) lateral mac. 2+2 tric without modified chaetae, 1+1 sens laterally and 1+1 mic near internal tric (Fig. 7B).

Abd. III with one (m3) central, and three (am6, pm6, p6) lateral mac. 3+3 tric without modified chaetae, 1+1 sens laterally, 1+1 mic near m3, ms not seen (Fig. 7B).

Abd. IV with five central mac (I, A5–6, B4–5) and six (D3, E1, E2p, E3–4, F3) lateral mac, 2+2 tric and about 18 long S-like chaetae anteriorly, without modified chaetae (Fig. 7C).

Abd. V with 15–18 mac and several mes to small mac, and 3+3 sens (Fig. 7D). Abd. VI not analysed. S-chaetae formula from Th. II to Abd. V: 2+ms, 2/1+ms, 2, 2, ≈15–18, 3; ps not seen, as sens on Abd. IV 1/3 as long as S-like chaetae (Figs 7A–D).

Legs (Figs 6E, G). Leg long; tita of leg III slightly longer than tita of legs I and II. Legs devoid of scales, covered with ordinary ciliated chaetae of various lengths, mic not seen. Trochanteral organ with 19–23 smooth, straight, unequal spine-like chaetae (Fig. 6E). The distal whorl of tita with 9–10 subequal ciliated mes, irregularly arranged, and usually dorso-apical clavate tenent hair present (two specimens claw III with pointed tenent hair). A smooth, thin and long chaeta close to the absent tenent hair. Ventro-distal smooth chaeta of tita III thick, erected, pointed, rather short. Claw rather slender and elongated. Unguis of all claws with two inner teeth, one-minute tooth at about 90 % from base of the claw, and a strong inner tooth at 40–46 %, and a pair of subequal basal teeth at about 30–34 % of inner edge from basis. Unguiculus approximately 2/3 as long as inner edge of the claw, rather swollen baso-externally, pointed apically, with one inner tooth and at least four minute outer teeth, often inconspicuous near the tip of its length (Fig. 6G).

Ventral tube (Figs 5I, 6A–C). Ventral tube three to four times longer than wide. Lateral flaps usually with 7–9+7–9 smooth chaetae, sometimes 1–2 ciliated present. In the holotype, 10 smooth and one ciliated chaeta present on one side (Fig. 5I). Anterior face with 7–9+7–9 ciliated chaetae, three of them apically larger than others (Fig. 6B); posterior face with 4 long, smooth chaetae apically, the middle chaetae with 4–6 long, smooth chaetae mixed with 5–6 mic arranged roughly asymmetrically, and 2–3 proximal chaetae, ciliated in the holotype (Fig. 6C) but smooth in 2 specimens (Fig. 6A).

Furcal complex (Figs 6D, F). Tenaculum with four large teeth of decreasing size from the basal to the distal one of each ramus, on a prominent, irregular body, with a postero-basal strong serrated chaeta bent distally. Mucrodens 1.15–1.42 times longer than manubrium. Furcula without smooth chaetae. Manubrium densely cover of ciliated chaetae both dorsally and ventrally. Manubrial plaque with 2+2 psp and five ciliated chaetae (Fig. 6D). Distal part of the ventral manubrium not clearly seen in all specimens. Dens without spines, annulated and covered with ciliated chaetae on both sides. Distal smooth part of dens as long as the mucro. Mucro strong and falcate, basal spine long, nearly reaching the tip of the mucronal tooth (Fig. 6F).

Genital plate. Female genital plate with 2+2 genital mic.

Coecobrya troglobia sp. nov. is restricted to the dark zone of the cave, where it was found in two chambers in an oligotrophic environment. Most individuals were found on the floor, on stalagmites and on the rock walls. The temperature in the dark zone was 21.4–23 °C and the relative humidity was about 75 %.

The name of the new species is derived from the Greek stem “trogle (τρώγλη)” which means “hole”, referring to the habitat of this new species which is restricted to the subterranean environment.

Coecobrya troglobia sp. nov. is also near to C. cavicta Nilsai & Zhang, 2017 from Satun province, southern Thailand in the number of mac of M series and Gr. II of dorsal head chaetotaxy, labial chaetae, number of sublobal hairs on maxillary outer lobe, number of mac on medio-medial area of Th.II, number of mac on Abd. III. However, Coecobrya troglobia sp. nov. is diffent from C. cavicta by having bigger body size, longer length of antennae, number of chaetae along cephalic groove, number of mac of dorsal tergits on Th. II (20–23 vs. 36–37), Th. III (24–27 vs. 35), Abd. II (2 vs. 3) and Abd. IV (11 vs. 18–20), number of inner teeth of claw (3 vs. 2) and number of smooth chaetae of trochanteral organ (19–23 vs. 15–16) (see Table 1). Coecobrya troglobia sp. nov. is close to C. whitteni sp. nov. from Tham Nayn Noi in Chum Phae district, Khon Kaen province, but they clearly differ from each other in a few morphological characters, see the detailed diagnosis in the remarks under C. whitteni sp. nov. and Table 1.

Holotype : male on slide. Thailand, Phetchabun province, Nong Phai district, Tham Tho, altitude 261 m a.m.s.l., 16.1231°N, 101.0222°E. 9.X.2019; S. Jantarit and A. Nilsai leg. (sample # THA_SJ_PNB06), dark zone of a cave, by entomological aspirator. Paratypes: same data as holotype, 12 specimens (1 male, 4 females and 7 subadults on slides). Additional material: same data as holotype, 8 specimens (in ethanol).

Holotype and 12 paratypes on slides deposited in NHM-PSU.

Habitus (Fig. 1C). Medium size Entomobryidae. Body length 1.6–2.1 mm (holotype 1.8 mm). No scales. Eyes absent. Color: whitish in alcohol, with orange pigmentation on head, body, legs and furca. Four antennal segments. Body slender not bent nor humped at the level of Th. II. Th. II slightly larger than Th. III. Abd. IV 3.70–4.25 times as long as Abd. III along dorsal midline.

Pseudopores (Figs 9E, 10A–C). Pseudopores present as round flat disks, smaller than mac sockets, except for the coxae and manubrium where psp are as large as mac sockets, present on various parts of the body: antennae, head, tergites, coxae and manubrium. On antennae, psp located ventro-apically between the tip of antennal segments and the chaetae of the apical row, or just below apical row of chaetae (2 psp on Ant. I, 2–3 psp on Ant. II, and 3 psp on Ant. III). On head, 1–2 psp located externally on each peri-antennal area. On tergites, 1+1 psp close to the axis from Th. II to Abd. IV (Figs 10A–C). On coxae, 1–2 psp on coxae I, 2–3 psp on coxae II and 1–2 psp on coxae III, located close to longitudinal rows of chaetae. On manubrium, 2+2 dorso-apical ones (Fig. 9E).

Clypeus and mouthparts (Figs 8A–C, E–G). Clypeal area with three long, smooth prefrontal; seven middle chaetae (two long smooth chaetae and five ciliated chaetae; 1+1 long lateral chaetae (Fig. 8G). Prelabral and labral chaetae 4/5, 5, 4, all thin and smooth; the three median chaetae of the first row longer than two lateral ones, two lateral chaetae 1/2.5 length of others on second row (Fig. 8A). Distal border of the apical non-granulated area of the labrum with a relatively narrow median U- or V-form intrusion into the granulated area dorsally; apical edge without spines (Fig. 8A). Ventro-distal complex of labrum well differentiated, asymmetrical, with 1+1 distal combs of 13–15 minute on the right side and 14–16 strong and larger teeth on the left side (Fig. 8C), and an axial pair of long sinuous tubules. Maxillary outer lobe with one basal chaeta, one apical chaeta (basal chaeta thicker than apical one) (34–44 µm vs. 12–15 µm) and four smooth sublobal hairs (Fig. 8F). Labial palp strongly modified for the genus, with 0, 5, 0, 4, 4 guards for papillae A–E. Lateral process of labial palp subcylindrical, as thick as normal chaetae, with tip beyond the apex of the labial papilla (Fig. 8B). Mandible apex strong, asymmetrical (left with four teeth, right with five teeth); molar plate with three strong pointed basal teeth, and 3–(5) smaller inner distal teeth, identical in both mandibles (Fig. 8E). Maxilla capitulum with a three-toothed claw and several stout ciliated lamellae; lamella 2 large and broad, lamella 3 well developed; several other lamellae present.

Antennae (Fig. 8D). Antennae extremely long, approximately 3.5–6.4 times as long as cephalic diagonal. Antennal segments ratio as I: II: III: IV. 1: 1.85: 1.76: 2.54 (N = 3). However, Ant II and III fused together in most cases. Antennal segments not subdivided nor annulated. Antennal chaetal types not analysed in detail. Smooth spiny mic at base of antennae: 3 dorsal, 3 ventral on Ant. I, 1 internal, 1 external and 1 ventral on Ant. II, 1 smooth ventral on Ant. I, smooth straight long chaetae on antennae present Ant. I ventrally with many smooth spiny mic of various sizes in its basal part, many subcylindrical, hyaline sens in its middle to apical part, and many long smooth straight chaetae. The paddle-like chaetae on Ant II absent. Ant. III organ with five sens not clearly seen in all specimens. Ant. IV without apical bulb. Subapical organite not distinctly knobbed, swollen, slightly enlarged apically, inserted dorsally (Fig. 8D).

Dorsal head chaetotaxy (Fig. 9D). Dorsal cephalic chaetotaxy with three antennal chaetae (An1, An3a, An3, An1 as mes); four anterior mac (A0, A2–3 and A5), three median (M1, M2 and M4) and eight sutural mac (S0, S1–7); Gr. II with 4(5) mac; A₀ as mac; 6–8+6–8 scale-like structures (usually 6+6) present below sutural mac, probably inside the integument; a pair of short cephalic trichobothria, external and close to the middle of the head (Fig. 9D).

Ventral head chaetotaxy (Figs 9A, B). Chaetae of labial basis almost all smooth (m₁m₂rel₁l₂) or (m_imrel₁l₂ sensu Zhang and Pan, 2020) (Fig. 9A) except m1(mi) ciliated in one side in two specimens (Fig. 9B), chaetae m1, e and l₁ subequal, r thin and shortest, and l₂ longest, m2 longer and thicker than m1. The r/m2 length ratio: 0.15–0.21 (Fig. 9A). Postlabial chaetae X₂, and X₄ smooth and minute chaetae, X, X₃ long and smooth and X₁ absent (Fig. 9A). On each side of the cephalic groove with 8–9 chaetae, of which the anterior five always long and smooth, 6^thand 8^th long and ciliated, 7^thand 9^th mics (Fig. 9A).

Tergite chaetotaxy (Figs 10A–D). Th. II with three (m1, m2, m2i) medio-medial, three (m4, m4p, m4i) medio-sublateral and 28–31 posterior mac; 1+1 ms and 2+2 sens antero-laterally (Fig. 10A).

Th. III with 29–36 mac. 2+2 sens laterally (Fig. 10A).

Abd. I with seven (a2–3, m2–4, m2i, m4p) mac, 1+1 ms and 1+1 sens laterally (Fig. 10B).

Abd. II with two (m3, m3e) central and one (m5) lateral mac, 2+2 tric without modified chaetae, 1+1 sens laterally and 1+1 mic near internal tric (Fig. 10B).

Abd. III with two (a2, m3) central, and three (am6, pm6, p6) lateral mac, 3+3 tric without modified chaetae, 1+1 sens laterally,1+1 mic near m3, ms present (Fig. 10B).

Abd. IV with eight central mac (I, M, A5–6, A5p, B4–6) and nine (D3, E1–4, F1–3, F3a) lateral mac, 2+2 tric and at least 8 long S-like chaetae, without modified chaetae (Fig. 10C).

Abd. V with at least 9 obvious mac mixed with several mes to small mac, and 3+3 sens (Fig. 10D). Abd. VI not analysed.

S-chaetae formula from Th. II to Abd. V: 2+ms, 2/1+ms, 2,2+ms, ≈8, 3; as and ps sens on Abd. IV 1/3 as long as S-like chaetae (Figs 10A–D).

Legs (Figs 8J, K). Leg long; tita of leg III slightly longer than tita of legs I and II. Legs devoid of scales, covered with ordinary ciliated chaetae of various lengths, mic not seen. Trochanteral organ with 17–23 smooth, straight, unequal spine-like chaetae (Fig. 8K). The distal whorl of tita III with 9–10 subequal ciliated mes, irregularly arranged, and dorso-apical pointed tenent hair (claw II–III clavate in one specimen). A smooth, thin and long chaeta close to tenent hair absent. Ventro-distal smooth chaeta of tita III thick, erected, pointed, rather short. Claw rather slender and elongated. Unguis of all claw with one inner tooth at 68 % from the base of claw; a pair of unequal basal teeth at about 50–52 % of inner edge from basis, outer tooth present at 40 % from base of the claw (Fig. 8J). Unguiculus approximately 2/3 as long as inner edge of the claw, pointed apically, devoid of inner and outer teeth (Fig. 8J).

Ventral tube (Figs 8H, I, 9C). Ventral tube about three times longer than wide. Lateral flaps with 7–8+7–8 chaetae (6–7+6–7 smooth chaetae and 0–2+0–2 ciliated chaetae present (Figs 8H–I, 9C). Anterior face with 6–7+6–7 ciliated chaetae, 2(3) of them larger than others (Fig. 8H); posteriorly with 4 apical long smooth chaetae, and about 8–9 proximal smooth chaetae mixed with long and mic chaetae arranged roughly asymmetrically (Fig. 9C).

Furcal complex (Figs 9E–G).Tenaculum with four large teeth of decreasing size from the basal to the distal one of each ramus, on a prominent, irregular body, with a postero-basal strong serrated chaeta bent distally. Mucrodens 1.22–1.31 times longer than manubrium. Furcula without smooth chaetae. Manubrium with a dense cover of ciliated chaetae both dorsally and ventrally. Manubrial plaque with 2+2 psp and five to six ciliate chaetae (Fig. 9E). Distal part of manubrium ventrally with 10–12 + 10–12 ciliate chaetae (Fig. 9G). Dens without spines, annulated and covered with ciliated chaetae on both sides. Distal smooth part of dens longer than mucro. Mucro strong and falcate, basal spine long, nearly reaching the tip of the mucronal tooth (Fig. 9F).

Genital plate. Female genital plate with 2+2 genital mic, male genital plate not clearly seen.

Coecobrya ellisi sp. nov. was found deep in a cave which has many chambers, on the muddy ground floor, on stalagmites and on wet rock walls. Many individuals were found feeding on the patches of bat guano in mesotrophic to eutrophic habitats. The relative humidity of the cave was 86–89% and the temperature was 25.8–27.5 °C. The cave where this species was found is located in an isolated limestone hill and has a narrow, vertical, entrance about 25 m deep which is equipped with iron ladders. The cave is approximately 250 m long and 30 m deep and many of the chambers are dug out and enlarged. Bad air, with a low oxygen level (<18%), was also detected in some chambers, including the one where the new species was found which is at the base of the iron ladders.

This species is named in honor of Martin Ellis, a British speleologist who played a role in the Tham Luang cave rescue in Thailand (in 2018), and for his outstanding contribution to the study of cave fauna in Thailand. Our biological surveys have benefited tremendously from his support, including the discovery of this new species.

Coecobrya ellisi sp. nov. is close to and shares most morphological characters with C. phitsanulokensis sp. nov. from Tham Yai Nakarat, Noen Mapang district, Phitsanulok province. The two caves where these new two species were discovered are only 55 km apart in a straight line. They are similar in chaetotaxy of dorsal head, number of sublobal hairs on maxillary outer lobe, labial chaetotaxy, medio-medial and medio-sublateral mac on Th. II, number of mac on Abd. I, Abd. III, pointed tenent hair, anterior face of ventral tube and number of chaetae on manubrium plaque. However, C. ellisi sp. nov. can be easily distinguished from C. phitsanulokensis sp. nov. by the number of An mac on dorsal head (3 vs. 5), number of central mac on Abd. II (2 vs 3(4), number of central mac on Abd. IV (8 vs. 9), lateral mac on Abd. IV (9 vs. 8), number of inner teeth of claw (3 vs. 2) and number of chaetae on ventro-distal part of manubrium (10–12 vs. 13) (Table 1). Moreover, C. ellisi sp. nov. possesses orange dots clearly pigmented on the antennae, head, body, legs and manubrium while all other troglomorphic Coecobrya species so far described in Thailand are devoid of any trace of pigmentation (Fig. 1C).

Holotype : female on slide. Thailand, Phitsanulok province, Noen Mapang district, Tham Yai Nakarat, altitude 85 m a.m.s.l., 16.5052°N, 100.6864°E. 7.X.2019; S. Jantarit, A. Nilsai, K. Sarakhamhaeng and K. Jantapaso leg. (sample # THA_SJ_PLK01), dark zone of a cave, by entomological aspirator. Paratypes: same data as holotype, 7 specimens (3 females and 4 subadults on slides). Additional material: same data as holotype, 13 specimens (in ethanol)

Holotype and seven paratypes on slides deposited in NHM-PSU.

Habitus (Fig. 1D). Medium size Entomobryidae. Body length 1.8–2.3 mm (holotype 1.8 mm). No scales. Eyes absent. Color: whitish in alcohol, without pigmentation. Four antennal segments. Body slender not bent nor humped at the level of Th. II. Th. II slightly larger than Th. III. Abd. IV 3.58–3.88 times as long as Abd. III along the dorsal midline.

Pseudopores (Figs 12H, 13A, B, D). Pseudopores present as round flat disks, smaller than mac sockets, except for the coxae and manubrium where psp are as large as mac sockets, present on various parts of the body: antennae, head, tergites, coxae and manubrium. On antennae, psp located ventro-apically between the tip of antennal segments and the chaetae of the apical row, or just below the apical row of chaetae (2 psp on Ant. I, 2–3 psp on Ant. II, and 3 psp on Ant. III). On the head, 1–2 psp located externally on each peri-antennal area. On tergites, 1+1 psp close to the axis from Th. II to Abd. IV (Figs 13A, B, 13D). On coxae, 1–2 psp on coxae I, 2–3 psp on coxae II and 1–2 psp on coxae III, located close to longitudinal rows of chaetae. On manubrium, 2+2 dorso-apical ones (Fig. 12H).

Clypeus and mouthparts (Figs 11A–C, F, 12A). Clypeal area with three long, smooth prefrontal chaetae; 9 middle chaetae (two long smooth chaetae, 7 small ciliated chaetae from mic to mes arranged asymmetrically), and two long, smooth lateral chaetae (Fig. 11A). Prelabral and labral chaetae 4/5, 5, 4, all thin and smooth; three median chaetae of the first and second rows longer than the two lateral ones (32–38 vs. 12–15 µm) (Fig. 11C). Distal border of the apical non-granulated area of the labrum with a relatively narrow median U- or V-form intrusion into the granulated area dorsally; apical edge without spines (Fig. 11C). Ventro-distal complex of labrum well differentiated, asymmetrical, with 1+1 distal combs 15–16 minute on the right side and 13 strong and larger teeth on the left side, and an axial pair of long sinuous tubules. Maxillary outer lobe with one basal chaeta, one apical chaeta (basal chaeta thicker than apical one) and four smooth sublobal hairs (65–70 vs. 25–32 µm) (Fig. 11F). Labial palp strongly modified for the genus, with 0, 5, 0, 4, 4 guards for papillae A–E. Lateral process of labial palp subcylindrical, as thick as normal chaetae, with tip beyond the apex of the labial papilla (Fig. 11B). Mandible apex blunt and strong, asymmetrical (left with four teeth, right with five teeth); molar plate with three strong pointed basal teeth, and 3–(5) smaller inner distal teeth, identical in both mandibles (Fig. 12A). Maxilla capitulum with a three-toothed claw and several stout ciliated lamellae; lamella 2 large and broad, lamella 3 well developed; several other lamellae present.

Antennae. Antennae long, approximately 3.1–4.2 times as long as cephalic diagonal. Antennal segments ratio as I: II: III: IV. 1: 0.5–0.73: 0.48–0.7: 0.41–0.68 (N = 6). Antennal segments not subdivided nor annulated. Antennal chaetal types not analyzed in detail. Ant. I ventrally with many smooth spiny mic of various sizes in its basal part, many subcylindrical, hyaline sens in its middle to apical part, and many long smooth straight chaetae. The paddle-like chaetae on Ant II absent. Ant. III organ with five sens not clearly seen in all specimens. Ant. IV without apical bulb. Subapical organite not distinctly knobbed, swollen, slightly enlarged apically, inserted dorsally.

Dorsal head chaetotaxy (Fig. 11E). Dorsal cephalic chaetotaxy with five antennal chaetae (An1–3, An3a2, An3a, An1 as mes), four anterior mac (A0, A2–3 and A5) three median (M1, M2 and M4) and eight sutural mac (S0, S1–S7); Gr. II with 4 or 5 mac; A₀ as mac; 5–7+5–7 scale-like structures present below sutural mac, probably inside the integument; a pair of short cephalic trichobothria, external and close to the middle of the head (Fig. 11E).

Ventral head chaetotaxy (Fig. 11D). Chaetae of labial basis all smooth (m₁m₂rel₁l₂), (m_imrel₁l₂ sensu Zhang and Pan, 2020), chaetae m1(m_i), e and l₁ subequal, r thin and shortest, and l₂ longest, m2 longer and thicker than m1. The ratio of r to m2: 0.13–0.19 (Fig. 11D). Postlabial chaetae X₂, X and X₄ minute chaetae, X₁ and X₃ absent. On each side of cephalic groove with 8–11 chaetae, of which the anterior five always long and smooth, others either smooth or finely ciliated, at least 3–4 minute chaetae always present on the posterior ones (Fig. 11D).

Tergite chaetotaxy (Figs 13A–D). Th. II with three (m1, m2, m2i) medio-medial, three (m4, m4p, m4i) medio-sublateral and 31–33 posterior mac; 1+1 ms and 2+2 sens antero-laterally (Fig. 13A).

Th. III with 32–33 mac. 2+2 sens laterally (Fig. 13A).

Abd. I with seven (a2–3, m4, m2–3, m2i, m4p) mac, 1+1 ms and 1+1 sens laterally (Fig. 13B).

Abd. II with 3(4) (a2, m3, m3ep, and m3e sometimes present) central and one (m5) lateral mac. 2+2 tric without modified chaetae, 1+1 sens laterally and 1+1 mic near internal tric (Fig. 13B).

Abd. III with two (a2, m3) central and three (am6, pm6, p6) lateral mac, 3+3 tric without modified chaetae, 1+1 sens laterally,1+1 mic near m3, ms present (Fig. 13B).

Abd. IV with nine central mac (I, M, A4–6, A5p, B4–6) and nine (D3, E1–4, E2p, F1–3) lateral mac, 2+2 tric and about 8 long S-like chaetae, without modified chaetae (Fig. 13D).

Abd. V with 12 obvious mac mixed with several mes to small mac, and 3+3 sens (Fig. 13C). Abd. VI not analysed.

S-chaetae formula from Th. II to Abd. V: 2+ms, 2/1+ms,2,2+ms, ≈8, 3; as and ps sens on Abd. IV 1/3 as long as S-like chaetae (Figs 13A–D).

Legs (Figs 12B, D). Leg long; tita of leg III slightly longer than tita of legs I and II. Legs devoid of scales, covered with ordinary ciliated chaetae of various lengths, mic not seen. Trochanteral organ with 19 smooth, straight, unequal spine-like chaetae (Fig. 12D). The distal whorl of tita III with 10 subequal ciliated mes, irregularly arranged, and dorso-apical pointed tenent hair. A smooth, thin and long chaeta close to tenent hair absent. Ventro-distal smooth chaeta of tita III thick, erected, pointed, rather short. Claw slender and elongated. Unguis of all claws without inner tooth, and a pair of subequal basal teeth at about 29–36 % of inner edge from basis. Unguiculus approximately 1/2 as long as the inner edge of the claw, rather swollen basally, pointed apically, devoid of inner tooth, with at least 3–4 minute outer teeth, often inconspicuous, at 3/4 of its length (Fig. 12B)

Ventral tube (Figs 12E, F). Ventral tube about four times longer than wide. Lateral flaps with 6–8+6–8 smooth chaetae (Fig. 12F). Anterior face with 6–7+6–7 ciliated chaetae, four of them larger than others (Fig. 12E); posterior face with 4 long, smooth apical chaetae and about 11 smooth chaetae arranged roughly asymmetrically, mixed with mic or small acuminate mes (Fig. 12F).

Furcal complex (Figs 12C, G, H). Tenaculum with four large teeth of decreasing size from the basal to the distal one of each ramus, on a prominent, irregular body, with a postero-basal strong serrated chaeta bent distally. Mucrodens 1.11–2.27 times longer than manubrium. Furcula without smooth chaetae. Manubrium with a dense cover of ciliated chaetae both dorsally and ventrally. Manubrial plaque with 2+2 psp and five to six ciliate chaetae (Fig. 12H). Distal part of manubrium ventrally with 13–15+13–15 ciliate chaetae (Fig. 12C). Dens without spines, annulated and covered with ciliated chaetae on both sides. Distal smooth part of dens slightly longer than mucro. Mucro strong and falcate, basal spine long, nearly reaching the tip of the mucronal tooth (Fig. 12G).

Genital plate . Female genital plate with 2+2 genital mic.

Coecobrya phitsanulokensis sp. nov. was found from the twilight zone (ca. 20 m from the cave entrance) to the dark zone of the cave on wet and muddy ground and on the decaying organic material inside the cave. The length of the main passage in the cave is about 300 m. The temperature was 26.2–27.9 °C, the soil temperature was 24.1–24.3 °C and the relative humidity in the cave was 78–89 %. The cave has a seasonal stream in it, but there was no water during our visit. This cave is developed in a very small isolated limestone hill (0.4 × 0.9 km) surrounded by a flood plain agricultural landscape, with at least seven other caves having been reported in this hill.

This species is named after the type locality, Phitsanulok province, where the material was collected.

Among the troglobitic Coecobrya species C. phitsanulokensis sp. nov. is similar to C. ellisi sp. nov. from Tham Tho, Nong Phai district, Phetchabun province. For the species diagnosis see the remarks under Coecobrya ellisi sp. nov. and Table 1.