Thailand • 1 larva; Trang Prov., Na Yong Distr., Wang Nam Rab resort; 07°34'32"N, 99°47'13"E; 142 m; 18.v.2017; leg. C. Suttinun; on slide; GBIFCH01556161; VMCMU • 1 larva; Trang Prov., Yan Tha Khao Distr., Klong Tha Ped; 07°29'33"N, 99°46'26"E; 50 m; 18.v.2017; leg. C. Suttinun; on slide; GBIFCH00980855; VMCMU • 9 larvae; Trang Prov., Huai Yod Distr., Khao Lak waterfall; 07°43'44"N, 99°44'21"E; 66 m; 18.v.2017; leg. C. Suttinun; 9 in alcohol; GBIFCH00980853, GBIFCH00763798; MZL.

Larva. Following combination of characters differentiate L. multus from other species of the group batakorum: head and thorax dorsally beige with grey-brown markings, abdomen dorsally grey-brown, laterally whitish with black markings, terga V and X brighter (Fig. 1d); hind protoptera well developed.

Figure 1. 

Labiobaetis mon sp. nov., larva: a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal view. Labiobaetis multus (Sumatra): d. Habitus, dorsal view. Scale bars: 1 mm (a, b); 100 µm (c).

The species differs from L. mon sp. nov. and L. lahu sp. nov. mainly by the colour pattern of the larva (Fig. 1d). The figured larva is from Sumatra (Kaltenbach and Gattolliat 2019b), its conspecificity with material from Thailand is supported by morphology and a COI sequence. Additionally, Fig. 1d is in line with a picture of the type series of L. multus (Müller-Liebenau 1984: fig. 24).

Malaysia (Selangor), Indonesia (Sumatra), Thailand (Fig. 32a).

Holotype. Thailand • larva; Phetchaburi Prov., Kaeng Krachan Distr., Huai Mae Kamoei; 12°58'42"N, 99°34'55"E; 119 m; 24.ii.2018; leg. C. Suttinun; on slide; GBIFCH00980857; VMCMU. Paratypes. 40 larvae; same data as holotype; 21 in alcohol; GBIFCH00980854, GBIFCH00763852; MZL; 19 in alcohol; GBIFCH00763797; VMCMU • 10 larvae; Ratchaburi Prov., Suan Phueng Distr., Swiss valley; 13°30'33"N, 99°17'12"E; 140 m; 26.v.2017; leg. C. Suttinun; 1 on slide; GBIFCH00592518; MZL; 9 in alcohol; GBIFCH00763808; VMCMU • 35 larvae; Ratchaburi Prov., Suan Phueng Distr., Pha Wo Tai; 13°30'57"N, 99°20'40"E; 118 m; 25.xi.2018; leg. C. Suttinun; 1 on slide; GBIFCH00980852; 34 in alcohol; GBIFCH00763799; MZL • 1 larva; Prachuab Khiri Khan Prov., Kui Buri Distr., Yang Chum; 12°04'40"N, 99°41'46"E; 57 m; 19.iv.2019; leg. C. Suttinun; on slide; GBIFCH00607177; VMCMU • 1 larva; Chanthaburi Prov., Khao Kitchakut Distr., Klong Krasue Yai; 12°52'36"N, 102°05'48"E; 38 m; 05.vi.2018; leg. C. Suttinun; on slide; GBIFCH00829296; MZL.

Thailand • 1 larva; Prachuab Khiri Khan Prov., Kui Buri Distr., Huai Sam Rong; 100 m; 12°03'50"N, 99°37'39"E; 19.iv.2019; leg. C. Suttinun; on slide; GBIFCH01556160; VMCMU.

Larva. Following combination of characters differentiate L. mon sp. nov. from other species of the group batakorum: head and thorax dorsally mostly dark brown with indistinct brighter pattern; abdomen dorsally brown to dark brown, paler in middle area, segment V not much brighter; hind protoptera present, well developed.

Larva (Figs 1a–c, 2, 3). Body length 3.6–4.8 mm. Cerci ~1/2 body length; paracercus ~1/3 of body length. Antenna: ~2× as long as head length.

Figure 2. 

Labiobaetis mon sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Labial palp; e. Hypopharynx and superlinguae; f. Maxilla; g. Maxillary palp; h. Left mandible i Right mandible. Scale bars: 20 µm (c, e, f, h, i); 10 µm (a, b, d, g).

Figure 3. 

Labiobaetis mon sp. nov., larva morphology: a. Hind leg; b. Hind claw; c. Section of hind femur; d. Section of hind tibia; e. Antennal base; f. Posterior margins of abdominal terga; g. Abdominal segment IX, posterior margin of tergum and sternum; h. Paraprocts; i, j. Tergalius IV; k. Left half of metanotum with hind protopteron. Scale bars: 50 µm (a); 20 µm (i); 10 µm (b–h, j).

Colouration (Fig. 1a–c). Head and thorax head dorsally mostly dark brown with indistinct pattern as in Fig. 1a. Abdomen dorsally brown to dark brown, paler in middle area, segment X pale brown. Fore protoptera brown. Thorax and abdomen ventrally off-white to pale brown, laterally with dark brown marking. Legs off-white to pale brown, femur medially, distally, and basally with grey-brown markings, tibia, and tarsus distally darker. Caudalii yellow-brown, dark brown section in distomedial part.

Antenna (Fig. 3e) with scape and pedicel sub cylindrical, distolateral process at scape well developed.

Labrum (Fig. 2a, b). Sub-rectangular, length 0.7× maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; pair of submedian setae, and submarginal arc of six long, simple setae on each side, 1^st and 2^nd setae closely together. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 2i). Incisor and kinetodontium fused. Incisor with three denticles; kinetodontium with four denticles, inner margin of innermost denticle with row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola convex, smooth. Tuft of setae on proximal corner of mola present.

Left mandible (Fig. 2h). Incisor and kinetodontium fused. Incisor with four denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola slightly convex, smooth. Tuft of setae on proximal corner of mola present.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 2e). Lingua approx. as long as superlinguae. Lingua longer than broad; medial tuft of stout setae well developed, short; medially expanded. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 2f, g). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and four short to long, simple setae. Maxillary palp longer than length of galea-lacinia; 2-segmented; palp segment II approx. as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment with distolateral excavation, apically rounded.

Labium (Fig. 2c, d). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ~9 spine-like seta; apex with two long and one medium, robust, apically pectinate setae; outer margin with ~4 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and ~2 short, simple setae in anteromedial area; dorsally with five or six long, spine-like setae near inner margin. Labial palp with segment I approx. as long as length of segments II and III combined. Segment II with broadly rounded, thumb-like, distomedial protuberance; distomedial protuberance 0.7× width of base of segment III; dorsally with row of ~4 spine-like setae near outer margin. Segment III conical; length approx. as maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera (Fig. 3k) present, well developed.

Legs (Fig. 3a–d). Ratio of foreleg segments 1.3:1.0:0.7:0.2, middle leg 1.3:1.0:0.6:0.3, hind leg 1.4:1.0:0.7:0.2. Femur. Fore femur length ~3× maximum width, middle and hind femur less wide. Outer margin with a row of 7–12 spine-like setae; length of setae ~0.2× maximum width of femur. Apex rounded, with pair of spine-like setae and short, stout, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch reduced or rudimentary on foreleg and well developed on middle and hind leg. Tibia. Outer margin with row of short, stout, apically rounded setae, distalmost seta larger. Inner margin with row of medium spine-like setae, on apex tuft of fine, simple setae. Patella-tibial suture present on basal 2/3 area. Tarsus. Outer margin with row of short, stout, apically rounded setae. Inner margin with row of curved, spine-like setae increasing in length distally. Claw with one row of ~12 denticles; distally pointed.

Abdominal terga (Fig. 3f, g). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I–IX with triangular spines, wide and short on I, less wide and longer toward end of abdomen.

Abdominal sterna (Fig. 3g). Posterior margin of sterna: I–VI smooth, without spines; VII–IX with small, triangular spines.

Tergalii (Fig. 3i, j). Present on segments I–VII. Margin with small denticles intercalating fine, simple setae. Tracheae mainly limited to trunk. Tergalius I as long as length of 2/3 II; tergalius IV as long as segments V and 1/2 VI combined; tergalius VII slightly longer than segment VIII.

Paraproct (Fig. 3h). Distally not expanded, with 9–15 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

Unknown.

The species is dedicated to the indigenous Mon people in Thailand.

Thailand (Fig. 32a).

Holotype. Thailand • larva; Tak Prov., Mueang Distr., Klong Lan Sang; 16°46'53"N, 99°01'16"E; 253 m; 25.xii.2017; leg. C. Suttinun; on slide; GBIFCH00596154; VMCMU. Paratypes. 2 larvae; same data as holotype; on slides; GBIFCH01223072, GBIFCH01223073; MZL • 2 larvae; Tak Prov., Mueang Distr., Oum Yom; 06°48'16"N, 99°01'19"E; 249 m; 26.xii.2017; leg. C. Suttinun; 1 on slide; GBIFCH01223071; 1 in alcohol; GBIFCH00763789; VMCMU • 8 larvae; Loei Prov., Wang Saphung Distr., Loei River; 17°18'04"N, 101°46'33"E; 256 m; 18.xii.2018; leg. C. Suttinun; 1 on slide; GBIFCH00607175; 7 in alcohol; GBIFCH00763787, GBIFCH00763790; VMCMU • 22 larvae; Chiang Mai Prov., Chiang Dao Distr., Kaeng Pantao; 19°17'02"N, 98°58'05"E; 403 m; 21.xi.2018 and 05.xi.2023; leg. C. Suttinun; 1 on slide; GBIFCH00607176; MZL; 21 in alcohol; GBIFCH00980856, GBIFCH00980858, GBIFCH00763791, GBIFCH00763786, GBIFCH00763871, GBIFCH00763874; VMCMU • 63 larvae; Tak Prov., Mae Sot Distr., Moei River; 16°42'04"N, 98°30'41"E; 194 m; 27.xii.2017; leg. C. Suttinun; in alcohol; GBIFCH00829295, GBIFCH00763785, GBIFCH00763788; VMCMU; GBIFCH00763851, GBIFCH00763873; MZL • 23 larvae; Ratchaburi Prov., Suan Phueng Distr., Pha Wo Tai; 13°30'57"N, 99°20'40"E; 118 m; 25.xi.2018; leg. C. Suttinun; in alcohol; GBIFCH00980851, GBIFCH00763807; VMCMU.

Larva. Following combination of characters differentiate L. lahu sp. nov. from other species of the group batakorum: thorax and abdomen dorsally dark grey with yellowish pattern as in Fig. 4a, especially yellowish oval markings on terga III and V; legs with reddish-brown spot distally on femur; hind protoptera present, well developed.

Figure 4. 

Labiobaetis lahu sp. nov., larva: a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal and ventral view. Scale bars: 1 mm (a, b); 100 µm (c).

Larva (Figs 4–6). Body length 4.2–5.0 mm. Cerci ~0.4 body length, paracercus ~0.3× body length. Antenna: ~2× as long as head length.

Figure 5. 

Labiobaetis lahu sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Labial palp; e. Hypopharynx and superlinguae; f. Maxilla; g. Maxillary palp; h. Left mandible; i. Right mandible. Scale bars: 20 µm (c, e, f, h, i); 10 µm (a, b, d, g).

Figure 6. 

Labiobaetis lahu sp. nov., larva morphology: a. Hind leg; b. Fore claw; c. Section of hind femur; d. Section of fore femur with femoral patch; e. Right half of metanotum with hind protopteron; f. Posterior margins of abdominal terga; g. Abdominal terga VIII and IX, posterolateral margin; h. Paraproct; i. Antennal base; j, k. Tergalius V. Scale bars: 50 µm (a, e); 20 µm (j); 10 µm (b–d, f–i).

Colouration (Fig. 4a–c). Thorax and abdomen dorsally dark grey with distinct yellowish markings as in Fig. 1a; abdominal segments V and X brighter. Fore protoptera yellowish and grey. Thorax and abdomen ventrally whitish-yellow; abdominal segments II–V with dark grey, arched marking; segments VI–IX dark grey. Legs off-white to yellowish, femur medially and basally with grey markings, distally with distinct reddish-brown spot, tibia and tarsus distally grey. Caudalii whitish-yellow, dark brown section in distomedial part.

Antenna (Fig. 6i) with scape and pedicel sub cylindrical, distolateral process at scape well developed.

Labrum (Fig. 5a, b). Sub-rectangular, length 0.7× maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; pair of submedian setae, and submarginal arc of four or five long, simple setae on each side, 1^st and 2^nd setae closely together. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 5i). Incisor and kinetodontium fused. Incisor with four denticles; kinetodontium with four denticles, inner margin of innermost denticle with row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola slightly convex, smooth. Tuft of setae on proximal corner of mola present.

Left mandible (Fig. 5h). Incisor and kinetodontium fused. Incisor with four denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola slightly convex, smooth. Tuft of setae on proximal corner of mola absent.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 5e). Lingua longer than superlinguae. Lingua longer than broad; medial tuft of stout setae well developed, short; in distal 1/2 expanded. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 5f, g). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and four short to long, simple setae. Maxillary palp longer than length of galea-lacinia; 2-segmented; palp segment II approx. as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment with distolateral excavation, apically constricted.

Labium (Fig. 5c, d). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ~9 spine-like seta; apex with three long, robust, apically pectinate setae; outer margin with ~4 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and one short, simple seta in anteromedial area; dorsally with five long, spine-like setae near inner margin. Labial palp with segment I ~0.8× length of segments II and III combined. Segment II with broadly rounded, thumb-like, distomedial protuberance; distomedial protuberance 0.7× width of base of segment III; dorsally with row of ~4 spine-like setae near outer margin. Segment III conical; length ~0.8× maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera (Fig. 6e) present, well developed.

Legs (Fig. 6a–d). Ratio of foreleg segments 1.4:1.0:0.6:0.2, middle leg 1.3:1.0:0.6:0.2, hind leg 1.2:1.0:0.7:0.2. Femur. Femur length ~3× maximum width. Outer margin with a row of 8–10 spine-like setae; length of setae ~0.2× maximum width of femur. Apex rounded, with pair of spine-like setae and short, stout, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch well developed on fore and middle leg, reduced or rudimentary on hind leg. Tibia. Outer margin with row of short, stout, apically rounded setae, distalmost seta larger. Inner margin with row of medium spine-like setae; on apex tuft of fine, simple setae. Patella-tibial suture present on basal 1/2. Tarsus. Outer margin with row of short, stout, apically rounded setae. Inner margin with row of curved, spine-like setae increasing in length distally. Claw with one row of 12 or 13 denticles; distally pointed.

Abdominal terga (Fig. 6f, g). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I–IX with triangular spines, wide and short on I, less wide and longer toward end of abdomen; terga VIII and IX additionally with posterolateral spines.

Abdominal sterna. Posterior margin of sterna: I–VI smooth, without spines; VII–IX with small, triangular spines.

Tergalii (Fig. 6j, k). Present on segments I–VII. Margin with small denticles intercalating fine, simple setae. Tracheae limited to trunk and few branches. Tergalius I as long as length of 1/2 II; tergalius IV as long as segments V and 1/3 VI combined; tergalius VII approx. as long as segment VIII.

Paraproct (Fig. 6h). Distally not expanded, with ~14 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

Unknown.

The species is dedicated to the indigenous Lahu people in Thailand.

Thailand (Fig. 32a).

Holotype. Thailand • larva; Ratchaburi Prov., Suan Phueng Distr., Bo Klueng; 13°31'27"N, 99°14'39"E; 180 m; 25.xi.2018; leg. C. Suttinun; on slide; GBIFCH00763877; VMCMU. Paratypes. 7 larvae; same data as holotype; 3 on slides; GBIFCH00829286; GBIFCH00829275; MZL; GBIFCH00607180; VMCMU; 4 in alcohol; GBIFCH00763853; MZL • 3 larvae; Ranong Prov., Mueang Distr., Rak Loi Waterfall; 09°41'27"N, 98°35'19"E; 78 m; 21.vi.2018; leg. C. Suttinun; 1 on slide; GBIFCH00829285; 2 in alcohol; GBIFCH00763855; VMCMU.

Larva. Following combination of characters differentiate L. tenasserimensis sp. nov. from other species of the group numeratus: abdomen dorsally rather uniform brown; hypopharynx with well-developed medial tuft; labial palp segment II lobed, segment III rather short; spines at posterior margin of abdominal tergites wide, apically rounded, mostly not fused.

Larva (Figs 7–9). Body length ~3.5 mm. Cerci ~1/2× body length; paracercus ~0.4× body length. Antenna: ~2× as long as head length.

Figure 7. 

Labiobaetis tenasserimensis sp. nov., larva: a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal and ventral view. Scale bars: 1 mm (a, b); 100 µm (c).

Figure 8. 

Labiobaetis tenasserimensis sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Labial palp; e. Hypopharynx and superlinguae; f. Maxilla; g. Maxillary palp; h. Left mandible; i. Right mandible. Scale bars: 20 µm (c, e, f, h, i); 10 µm (a, b, d, g).

Figure 9. 

Labiobaetis tenasserimensis sp. nov., larva morphology: a. Middle leg; b. Outer margin of middle femur; c. Inner margin of middle femur; d. Outer margin of middle tibia; e. Inner margin of middle tibia; f. Middle claw; g. Posterior margins of abdominal terga; h. Paraproct; i, j. Tergalius IV; k. Antennal base. Scale bars: 50 µm (a); 20 µm (i); 10 µm (b–h, j, k).

Colouration (Fig. 7a–c). Head and thorax dorsally beige, abdomen dorsally rather uniform brown. Fore protoptera beige with paler striation. Head and thorax ventrally beige, abdomen ventrally brown. Legs off-white to pale grey-brown, femur medially slightly darker. Caudalii pale grey-brown with dark brown band in distal 1/2.

Antenna (Fig. 9k) with scape and pedicel sub cylindrical, distolateral process at scape absent.

Labrum (Fig. 8a, b). Sub-rectangular, length 0.7× maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; pair of submedian setae, and submarginal arc of four or five long, simple setae on each side, 1^st and 2^nd setae closely together. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 8i). Incisor and kinetodontium fused. Incisor with four denticles; kinetodontium with three denticles, inner margin of innermost denticle with row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola with pronounced hump. Tuft of setae on proximal corner of mola present. Fine setae scattered along basal margin of mola.

Left mandible (Fig. 8h). Incisor and kinetodontium fused. Incisor with four denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola convex, smooth. Tuft of setae on proximal corner of mola present.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 8e). Lingua longer than superlinguae. Lingua longer than broad; medial tuft of stout setae well developed. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin; strongly sclerotised along laterobasal margin.

Maxilla (Fig. 8f, g). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and two or three medium to long simple setae. Maxillary palp longer than length of galea-lacinia; 2-segmented; palp segment II approx. as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment without distolateral excavation, apically slightly pointed.

Labium (Fig. 8c, d). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ~8 robust, spine-like seta, distalmost seta much longer; apex with two long and one medium, robust, apically pectinate setae, and one short seta; outer margin with ~4 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and two short, simple setae in anteromedial area; dorsally with five long, spine-like setae near inner margin. Labial palp with segment I ~0.9× length of segments II and III combined. Segment II with lobed, thumb-like, distomedial protuberance; distomedial protuberance 0.8× width of base of segment III; dorsally with row of 4–6 spine-like setae near outer margin. Segment III slightly pentagonal; length ~0.8× maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera vestigial.

Legs (Fig. 9a–f). Ratio of foreleg segments 1.4:1.0:0.8:0.3, middle leg 1.3:1.0:0.7:0.3, hind leg 1.4:1.0:0.6:0.3. Femur. Femur length ~3× maximum width. Outer margin with row of five or six spine-like setae and submarginally partial 2^nd row; length of setae ~0.2× maximum width of femur. Apex rounded, with pair of spine-like setae and short, stout, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch absent or rudimentary on all legs. Tibia. Outer margin with row of short, stout, apically rounded setae, distalmost seta larger. Inner margin with two rows of medium spine-like setae; on apex tuft of fine, simple setae. Patella-tibial suture present on basal 1/2. Tarsus. Outer margin almost bare. Inner margin with row of curved, spine-like setae increasing in length distally. Claw with one row of ~14 denticles; distally pointed.

Abdominal terga (Fig. 9g). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I–IX with wide, apically rounded spines, mostly not fused with each other; VI–IX more subtriangular, apically rounded.

Abdominal sterna (Fig. 7c). Posterior margin of sterna: I–V smooth, without spines; VI–IX with triangular, apically rounded spines, similar to spines on tergites.

Tergalii (Fig. 9i, j). Present on segments II–VII. Margin with small denticles intercalating fine, simple setae. Tracheae limited to main trunk. Tergalius IV as long as segments V and 1/2 VI combined; tergalius VII as long as segments VIII and 1/2 IX combined.

Paraproct (Fig. 9h). Distally not expanded, with ~11 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

Unknown.

The most similar species is L. paranumeratus Kaltenbach & Gattolliat, 2019 from Sumatra. The following characters distinguish the larvae of both species (see Kaltenbach and Gattolliat 2019b: 62, figs 31, 32): dorsal colour pattern of larval abdomen rather uniform brown in L. tenasserimensis sp. nov. (brown with segment V dark reddish-brown and segment II with dark reddish-brown streaks in L. paranumeratus); spines on posterior margins of abdominal tergites wide, rounded, mostly with small gaps between them in L. tenasserimensis sp. nov. (wide, rounded and mostly fused in L. paranumeratus); hypopharynx with medial tuft well developed in L. tenasserimensis sp. nov. (poorly developed in L. paranumeratus); setae at outer margin of tibia apically rounded, smooth in L. tenasserimensis sp. nov. (apically rounded and with minute serration in L. paranumeratus).

The species name is derived from the name of the Tenasserim mountain range where it was collected.

Thailand (Fig. 32b).

Holotype. Thailand • larva; Petchburi Prov., Kaeng Krachan Distr., Huai Mae Kamoei; 12°58'42"N, 99°34'55"E; 119 m; 24.ii.2018; leg. C. Suttinun; on slide; GBIFCH01223079; VMCMU. Paratypes. 13 larvae; same data as holotype; 2 on slides; GBIFCH00829290, GBIFCH00829279; MZL; 11 in alcohol; GBIFCH00763867; VMCMU • 4 larvae; Kanchanaburi Prov., Thong Pha Phum Distr., Pra Chum Mai; 14°34'58"N, 98°34'52"E; 269 m; 25.v.2017; leg. C. Suttinun; 1 on slide; GBIFCH01223081; VMCMU; 3 in alcohol; GBIFCH00829284, GBIFCH00763860; VMCMU • 2 larvae; Ratchaburi Prov., Suan Pheung Distr., Kang Som Maew; 13°24'22"N, 99°16'44"E; 207 m; 24.xi.2018; leg. C. Suttinun; 1 on slide; GBIFCH00829278; MZL; 1 in alcohol; GBIFCH00829291; VMCMU • 1 larva; Prachuab Khiri Khan Prov., Kui Buri Dist., Huai Sam Rong; 100 m; 12°03'50"N, 99°37'39"E; 19.iv.2019; leg. C. Suttinun; in alcohol; GBIFCH00829287; VMCMU • 6 larvae; Petchburi Prov., Kaeng Krachan Distr., Huai Sat Yai; 12°38'14"N, 99°30'59"E; 162 m; 25.ii.2018; leg. C. Suttinun; in alcohol; GBIFCH00829277, GBIFCH00763858; VMCMU • 7 larvae; Petchburi Prov., Kaeng Krachan Distr., Huai Mae Priang; 12°46'03"N, 99°34'54"E; 142 m; 24.ii.2018; leg. C. Suttinun; in alcohol; GBIFCH00829280, GBIFCH00829274; VMCMU; GBIFCH00763859; MZL • 8 larvae; Ratchaburi Prov., Suan Pheung Distr., Pha Wo Tai; 13°30'57"N, 99°20'40"E; 118 m; 25.xi.2018; leg. C. Suttinun; in alcohol; GBIFCH00829283, GBIFCH00763854, GBIFCH00763861; VMCMU • 4 larvae; Ranong Prov., Mueang Distr., Klong Nok Ngang; 09°42'22"N, 98°34'39"E; 11 m; 21.vi.2018; leg. C. Suttinun; in alcohol; GBIFCH00829273, GBIFCH00763856; VMCMU • 7 larvae; Ratchaburi Prov., Suan Pheung Distr., Swiss valley; 13°30'33"N, 99°17'12"E; 140 m; 26.v.2017; leg. C. Suttinun; in alcohol; GBIFCH00829282, GBIFCH00763857, GBIFCH00763865, GBIFCH00763866; MZL • 1 larva; Ratchaburi Prov., Suan Pheung Distr., Bo Wee resort; 13°28'41"N, 99°14'55"E; 184 m; 24.xi.2018; leg. C. Suttinun; in alcohol; GBIFCH00829289; VMCMU • 2 larvae; Loei Prov., Wang Saphung Distr., Ban Nam Thob; 17°16'11"N, 101°35'51"E; 318 m; 17.xii.2018; leg. C. Suttinun; in alcohol; GBIFCH00829281, GBIFCH00763862; MZL • 3 larvae; Chanthaburi Prov., Khao Khitchakut Distr., Klong Krasue Yai; 12°52'36"N, 102°05'48"E; 38 m; 05.vi.2018; leg. C. Suttinun; in alcohol; GBIFCH00829276, GBIFCH00763864; VMCMU • 1 larva; Prachuap Khiri Khan Prov., Kui Buri Distr., Huai Sam Rong; 12°03'82"N, 99°37'64"E; 103 m; 19.iv.2019; leg. C. Suttinun; on slide; GBIFCH00596153; VMCMU • 1 larva; Prachuap Khiri Khan Prov., Kui Buri Distr., Klong Kui; 12°08'17"N, 99°39'77"E; 104 m; 19.iv.2019; leg. C. Suttinun; on slide; GBIFCH01223080; VMCMU.

Larva. Following combination of characters differentiate L. angularis sp. nov. from other species of the group numeratus: abdomen dorsally dark grey-brown, laterally off-white; left mandible with angular hump at margin between prostheca and mola; claw with 14–17 denticles; spines at posterior margin of abdominal tergites wide, apically rounded.

Larva (Figs 10–12). Body length ~3.3 mm. Cerci ~1/2× body length; paracercus ~0.4× body length. Antenna: ~2× as long as head length.

Figure 10. 

Labiobaetis angularis sp. nov., larva: a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal and ventral view. Scale bars: 1 mm (a, b); 100 µm (c).

Figure 11. 

Labiobaetis angularis sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Labial palp; e. Hypopharynx and superlinguae; f. Maxilla; g. Maxillary palp; h. Left mandible; i. Right mandible; j. Section of left mandible. Scale bars: 20 µm (c, e, f, h, i); 10 µm (a, b, d, g).

Figure 12. 

Labiobaetis angularis sp. nov., larva morphology: a. Middle leg; b. Middle tarsus and claw; c. Antennal base; d. Abdominal sterna VII–IX; e. Posterior margins of abdominal terga I, V, VIII; f. Paraproct; g. Left half of metanotum with vestigial hind protopteron; h–j. Tergalius IV. Scale bars: 50 µm (a); 20 µm (g, h); 10 µm (b–f, h–j).

Colouration (Fig. 10a–c). Head and thorax dorsally dark grey-brown with grey-brown and grey markings; abdomen dorsally dark grey-brown, segment X paler, segments I–VIII laterally off-white. Fore protoptera dark grey and grey-brown. Head and thorax ventrally mainly grey; abdomen ventrally dark grey-brown, segments I and X paler, segments II–V medially paler, segments I–VIII laterally off-white. Legs off-white, femur distomedially with grey-brown band, tibia with long grey-brown streak. Caudalii pale grey with dark grey-brown band in distal 1/2.

Antenna (Fig. 12c) with scape and pedicel sub cylindrical, distolateral process at scape absent.

Labrum (Fig. 11a, b). Sub-rectangular, length 0.7× maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; pair of submedian setae, and submarginal arc of ~7 long, simple setae on each side, 1^st and 2^nd setae closely together. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 11i). Incisor and kinetodontium fused. Incisor with four denticles; kinetodontium with four denticles, inner margin of innermost denticle with row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola with pronounced hump. Tuft of setae on proximal corner of mola present. Fine setae scattered along basal margin of mola.

Left mandible (Fig. 11h). Incisor and kinetodontium fused. Incisor with four denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola with angular hump. Tuft of setae on proximal corner of mola present.

Both mandibles with lateral margins slightly convex.

Hypopharynx and superlinguae (Fig. 11e). Lingua approx. as long as superlinguae. Lingua longer than broad; medial tuft of stout setae well developed, short. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin; strongly sclerotised along laterobasal margin.

Maxilla (Fig. 11f, g). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and three or four medium to long simple setae. Maxillary palp longer than length of galea-lacinia; 2-segmented; palp segment II ~1.2× length of segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment without distolateral excavation, apically slightly pointed.

Labium (Fig. 11c, d). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with 9–11 robust, spine-like seta, distalmost seta much longer; apex with three long, robust, apically pectinate setae; outer margin with ~4 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and ~3 medium, simple setae in anteromedial area; dorsally with six long, spine-like setae near inner margin. Labial palp with segment I ~0.9× length of segments II and III combined. Segment II with lobed, thumb-like, distomedial protuberance; distomedial protuberance 0.9× width of base of segment III; dorsally with row of ~5 spine-like setae near outer margin. Segment III slightly pentagonal, apically truncate; length ~1.1× maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera (Fig. 12g) vestigial.

Legs (Fig. 12a, b). Ratio of foreleg segments 1.3:1.0:0.6:0.3, middle leg 1.3:1.0:0.7:0.3, hind leg 1.4:1.0:0.8:0.3. Femur. Femur length ~2.7× maximum width. Outer margin with row of 4–6 spine-like setae and submarginally partial 2^nd row; length of setae ~0.27× maximum width of femur. Apex rounded, with pair of spine-like setae and short, stout, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch absent on all legs. Tibia. Outer margin with row of short, stout, apically rounded setae, sometimes almost bare, distalmost seta larger. Inner margin with two rows of medium spine-like setae; on apex tuft of fine, simple setae. Patella-tibial suture present on basal 1/2. Tarsus. Outer margin with row of short, apically rounded setae, sometimes almost bare. Inner margin with row of curved, spine-like setae increasing in length distally. Claw with one row of 14–17 denticles; distally pointed.

Abdominal terga (Fig. 12e). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I–IX with wide, apically rounded spines, partly fused with each other.

Abdominal sterna (Fig. 12d). Posterior margin of sterna: I–VI smooth, without spines; VII–IX with triangular spines.

Tergalii (Fig. 12h– j). Present on segments II–VII. Margin with small denticles intercalating fine, simple setae. Tracheae limited to main trunk. Tergalius IV as long as segments V and VI combined; tergalius VII as long as segments VIII and 1/2 IX combined.

Paraproct (Fig. 12f). Distally not expanded, with ~13 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

Unknown.

The Latin word angularis, meaning angular, refers to the unique angular hump at the margin between prostheca and mola of the left mandible.

Thailand (Fig. 32b).

Holotype. Thailand • larva; Patthalung Prov., Ton Sa Tor; 07°11'43"N, 100°04'18"E; 51 m; 12.iii.2016; leg. C. Suttinun; on slide; GBIFCH00829272; VMCMU. Paratype. 1 larva; same data as holotype; on slide; GBIFCH00763863; MZL.

Larva. Following combination of characters differentiate L. tonsator sp. nov. from other species of the group numeratus: abdomen dorsally grey-brown, segment II distomedially with dark grey-brown spot, segment V dark brown; pedicellus basally with dark brown hypodermal colouration; claw with 12–16 denticles; spines at posterior margin of abdominal tergites wide, apically rounded, mostly not fused.

Larva (Figs 13–15). Body length 3.3–3.6 mm. Caudalii: broken. Antenna: ~2× as long as head length.

Figure 13. 

Labiobaetis tonsator sp. nov., larva: a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal view. Scale bars: 1 mm (a, b); 100 µm (c).

Figure 14. 

Labiobaetis tonsator sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Labial palp; e. Hypopharynx and superlinguae; f. Maxilla; g. Maxillary palp; h. Left mandible; i. Right mandible. Scale bars: 20 µm (c, e, f, h, i); 10 µm (a, b, d, g).

Figure 15. 

Labiobaetis tonsator sp. nov., larva morphology: a. Middle leg; b. Outer margin of middle femur; c. Inner margin of middle femur; d. Inner margin of middle tibia; e. Outer margin of middle tibia; f. Fore tarsus and claw; g. Posterior margins of abdominal terga; h, i. Tergalius III; j. Paraproct; k. Antennal base. Scale bars: 50 µm (a); 20 µm (h); 10 µm (b–g, i–k).

Colouration (Fig. 13a–c). Head and thorax dorsally yellow-grey with grey markings as in Fig. 13a, particularly with grey, round dot at base of fore protoptera; abdomen dorsally grey-brown, laterally yellow-grey, segment X paler, segment V dark brown, segment II distomedially with dark grey-brown, roundish spot, laterally dark grey-brown. Fore protoptera yellow-grey. Head, thorax and abdomen ventrally mainly dark grey, segment X paler, abdomen laterally yellow-grey. Legs pale grey, femur distomedially with grey and yellow markings, tibia distomedially with grey area. Caudalii whitish-yellow.

Antenna (Fig. 15k) with scape and pedicel sub cylindrical, distolateral process at scape absent.

Labrum (Fig. 14a, b). Sub-rectangular, length 0.7× maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; pair of submedian setae, and submarginal arc of ~9 long, simple setae on each side, 1^st and 2^nd setae closely together. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 14i). Incisor and kinetodontium fused. Incisor with four denticles; kinetodontium with three denticles, inner margin of innermost denticle with row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola with pronounced hump. Tuft of setae on proximal corner of mola present. Fine setae scattered along basal margin of mola.

Left mandible (Fig. 14h). Incisor and kinetodontium fused. Incisor with four denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola slightly convex. Tuft of setae on proximal corner of mola present.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 14e). Lingua slightly longer than superlinguae. Lingua longer than broad; medial tuft of stout setae well developed, short. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin; strongly sclerotised along laterobasal margin.

Maxilla (Fig. 14f, g). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and four medium to long simple setae. Maxillary palp longer than length of galea-lacinia; 2-segmented; palp segment II approx. as long as segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment without distolateral excavation, apically slightly pointed.

Labium (Fig. 14c, d). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ~9 robust, spine-like seta, distalmost seta much longer; apex with three long, robust, apically pectinate setae and one short, robust seta; outer margin with ~4 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and ~3 medium, simple setae in anteromedial area; dorsally with five or six long, spine-like setae near inner margin. Labial palp with segment I ~0.8× length of segments II and III combined. Segment II with slightly elongated thumb-like, distomedial protuberance; distomedial protuberance 0.8× width of base of segment III; dorsally with row of five spine-like setae near outer margin. Segment III slightly elongate, conical, apically truncate; length approx. equal to maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera vestigial.

Legs (Fig. 15a–f). Ratio of foreleg segments 1.2:1.0:0.6:0.2, middle leg 1.1:1.0:0.5:0.2, hind leg 1.2:1.0:0.5:0.2. Femur. Femur length ~3× maximum width. Outer margin with row of 5–7 spine-like setae and submarginally partial 2^nd row; length of setae ~0.27× maximum width of femur. Apex rounded, with pair of spine-like setae and short, stout, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch absent on all legs. Tibia. Outer margin with row of few short, stout, apically blunt setae, distalmost seta larger. Inner margin with two rows of medium spine-like setae; on apex tuft of fine, simple setae. Patella-tibial suture present on basal 1/2. Tarsus. Outer margin with row of short, apically blunt setae, sometimes almost bare. Inner margin with row of curved, spine-like setae increasing in length distally. Claw with one row of 12–16 denticles; distally pointed.

Abdominal terga (Fig. 15e). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I–IX with wide, toward end of abdomen subtriangular, apically rounded spines, rarely fused with each other.

Abdominal sterna . Posterior margin of sterna: I–VI smooth, without spines; VII–IX with wide triangular spines.

Tergalii (Fig. 15h, i). Present on segments II–VII. Margin with small denticles intercalating fine, simple setae. Tracheae extending from main trunk to inner and outer margins. Tergalius IV as long as segments V and 1/2 VI combined; tergalius VII as long as segments VIII and 1/2 IX combined.

Paraproct (Fig. 15j). Distally not expanded, with ~17 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

Unknown.

The species name is derived from the name of the village Ton Sa Tor, where it was collected (type locality).

Thailand (Fig. 32b).

Thailand • 3 larvae; Ranong Prov., Mueang Distr., Punyaban Waterfall; 10°03'54"N, 98°40'13"E; 52 m; 19.vi.2018; leg. C. Suttinun; on slides; GBIFCH01223074, GBIFCH00596156; VMCMU; GBIFCH00592514; MZL • 9 larvae; Ranong Prov., Mueang Distr., Huai Por Ta Hin Rao; 09°52'08"N, 98°37'32"E; 20 m; 20.vi.2018; leg. C. Suttinun; in alcohol; GBIFCH00763804; VMCMU; GBIFCH00763803; MZL.

Larva. Following combination of characters differentiate L. paraoperosus from other species of the group operosus: maxillary palp much longer than galea-lacinia, segment II with slight distolateral excavation; labial palp segment II with broad thumb-like, apically rounded distolateral protuberance; labial palp segment III oblong.

The larva has no morphological difference to L. paraoperosus from Indonesia (Sumatra), but there is a genetic distance of 12% (COI, K2P).

Thailand (Fig. 32c), but L. paraoperosus is known from Sumatra (Indonesia).

Holotype. Thailand • larva; Yasothon Prov., Kut Chum Distr., Huai Naso; 15°57'08"N, 104°18'12"E; 125 m; 11.08.2014; leg. B. Boonsoong; on slide; GBIFCH01221811; VMCMU. Paratypes. 9 larvae, 1 male imago (reared from larva); same data as holotype; 2 larvae on slides; GBIFCH00592508, GBIFCH00592509; MZL; 7 larvae in alcohol; GBIFCH00975862; VMCMU; 1 imago in alcohol; VMCMU • 1 larva; Kanchanaburi Prov., Thong Pha Phum Distr., Pra Chum Mai; 14°34'58"N, 98°34'52"E; 269 m; 25.v.2017; leg. C. Suttinun; on slide; GBIFCH01223084; MZL.

Larva. Following combination of characters differentiate L. nisaratae sp. nov. from other species of the group operosus: abdomen dorsally brown, segments I–IV with paler areas as in Fig. 16a, b, d, segments VII and X pale; labial palp segment II with elongated, apically rounded, distomedial protuberance, protuberance longer than base of segment III; femoral patch absent on foreleg, well-developed on middle and hind leg.

Figure 16. 

Labiobaetis nisaratae sp. nov., larva: a. Habitus male, dorsal view; b. Habitus female, dorsal view; c. Habitus, ventral view; d. Abdomen, dorsal view. Labiobaetis operosus, larva, holotype: e. Labium (Malaysia). Scale bars: 1 mm (a–c); 100 µm (d); 20 µm (e).

Larva (Figs 16–18). Body length 2.9–5.3 mm. Cerci: ~2/3 of body length. Paracercus: ~0.4× body length. Antenna: ~2× as long as head length.

Figure 17. 

Labiobaetis nisaratae sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Labial palp; e. Hypopharynx and superlinguae; f. Maxilla; g. Maxillary palp; h. Left mandible i Right mandible. Scale bars: 50 µm (c–e); 20 µm (f, h, i); 10 µm (a, b, g).

Figure 18. 

Labiobaetis nisaratae sp. nov., larva morphology: a. Fore leg; b. Section of fore femur; c. Section of fore tibia; d. Fore claw; e. Middle leg, femoral patch; f. Hind leg, femoral patch; g. Antennal base; h. Tergalius VII; i, j. Tergalius V; k. Posterior margins of abdominal terga; l. Paraproct. Scale bars: 50 µm (a, g–i); 10 µm (b–f, j–l).

Colouration (Fig. 16a–d). Head and thorax dorsally dark brown with some paler areas; abdomen dorsally brown to dark brown, segments I–IV with paler areas, VII and X pale. Fore protoptera dark brown. Head, thorax and abdomen ventrally beige. Legs off-white to pale brown, femur distomedially with yellow-brown spot. Caudalii off-white to pale brown, with dark brown band in middle part. Cerci distally annulated.

Antenna (Fig. 18g) with scape and pedicel sub cylindrical, distolateral process at scape well developed.

Labrum (Fig. 17a, b). Sub-rectangular, length 0.6× maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; submarginal arc of ~9 long, feathered setae on each side. Ventrally with marginal row of setae composed of anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 17i). Incisor and kinetodontium fused. Incisor with five denticles; kinetodontium with three denticles. Prostheca robust, apically denticulate. Margin between prostheca and mola slightly convex, with few minute denticles. Tuft of setae on proximal corner of mola present.

Left mandible (Fig. 17h). Incisor and kinetodontium fused. Incisor with four denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola slightly convex, with minute denticles. Tuft of setae on proximal corner of mola present.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 17e). Lingua slightly longer than superlinguae, longer than broad; medial tuft of stout setae poorly developed. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 17f, g). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and three or four medium to long simple setae. Maxillary palp longer than length of galea-lacinia; 2-segmented; palp segment II ~1.2× length of segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment with well-developed distolateral excavation.

Labium (Fig. 17c, d). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with eight or nine robust, spine-like setae, distalmost seta much longer; apex with two long and one medium, robust, apically pectinate setae and one short, robust seta; outer margin with four spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and four medium, simple setae in medial and anteromedial area; dorsally with four long, spine-like setae near inner margin. Labial palp with segment I approx. as long as segments II and III combined. Segment II with elongated thumb-like, apically rounded, distomedial protuberance; distomedial protuberance 1.1× width of base of segment III; dorsally with row of three or four spine-like setae near outer margin. Segment III slightly pentagonal, apically truncate; length ~1.2× maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera (Fig. 19g) well developed.

Figure 19. 

Labiobaetis nisaratae sp. nov., male imago: a. Habitus, lateral; b. Head and thorax, lateral; c. Genitalia; d. Fore wing; e. Hind wing (same proportion as d); f. Hind wing (augmented); g. Metanotum with hind protoptera. Scale bars: 1 mm (a, b, d, e); 0.5 mm (g); 100 µm (c, f).

Legs (Fig. 18a–f). Ratio of foreleg segments 1.3:1.0:0.5:0.2, middle leg 1.3:1.0:0.5:0.2, hind leg 1.4:1.0:0.5:0.2. Femur. Femur length ~4× maximum width. Outer margin with row of nine or ten spine-like setae; length of setae ~0.18× maximum width of femur. Apex rounded, with pair of spine-like setae and short, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch absent on foreleg and well developed on middle and hind legs. Tibia. Outer margin with row of many marginal and submarginal, short, apically blunt setae, distalmost seta larger. Inner margin with two rows of medium spine-like setae; on apex tuft of fine, simple setae. Patella-tibial suture present on basal 1/2. Tarsus. Outer margin with row of short, apically blunt setae. Inner margin with row of curved, short to medium, spine-like setae increasing in length distally. Claw with one row of 10–12 denticles; distally pointed.

Abdominal terga (Fig. 18k). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I with rudimentary spines, II–IX with triangular, pointed spines, becoming longer, narrower and sharper pointed toward end of abdomen; II–IX posterolaterally with one, two, or several minute to small spines, increasing in number toward end of abdomen.

Abdominal sterna . Posterior margin of sterna: I–VII smooth, without spines; VIII and IX with triangular spines.

Tergalii (Fig. 18h–j). Present on segments I–VII. Margin with small denticles intercalating fine, simple setae. Tracheae partly extending from main trunk to inner and outer margins. Tergalius I approx. as long as segment II; tergalius IV approx. as long as segments V and VI combined; tergalius VII as long as segments VIII and 1/2 IX combined.

Paraproct (Fig. 18l). Distally not expanded, with ~17 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

Male imago (Fig. 19a–f). Body length 2.5 mm, forewing length ~2.5 mm, hind wing length ~0.5 mm.

Colouration. Head and thorax beige with brown markings, turbinate eyes beige, shaft pink. Legs bluish. Wings and venation hyaline. Abdominal segments I–VI dorsally and ventrally bluish, segments VII, IX, and X off-white to beige, segment VIII light brown; abdominal segments dorsally with narrow brown bands at posterior margins. Cerci bluish.

Forewing . Pterostigma with seven cross-veins, first two reaching subcostal vein. Double intercalary veins mostly shorter than distance between corresponding main veins at wing margin.

Hind wing . Much smaller than forewing, with two longitudinal veins.

Genitalia. Basal segment of gonostylus (unistyliger) distally expanded at inner margin; segments I and II almost completely fused; segment I basally with protuberance at inner margin; small constriction at base of segment II; segment III slightly ovoid, with strong constriction at base, cross-section dimension slightly smaller than distal margin of segment II. Styliger plate between unistyligers well developed, distal margin straight.

The larva of L. nisaratae sp. nov. is very similar to L. operosus. The only clear difference is in the shape of labial palp segment II, where the distomedial protuberance in L. nisaratae sp. nov. is elongated, longer than the base of segment III (~1.1×). In L. operosus, the distomedial protuberance of segment II is shorter than the base of segment III (~0.8×) and stouter than in L. nisaratae sp. nov.

The name of this species is dedicated to Assoc. Prof. Dr. Nisarat Tungpairojwong (Department of Biology, Khon Kean University) for her outstanding contributions to the systematics of aquatic insects in Thailand.

Thailand (Fig. 32c).

Holotype. Thailand • larva; Kanchanaburi Prov., Thong Pha Phum Distr., Pra Chum Mai; 14°34'58"N, 98°34'52"E; 269 m; 25.v.2017; leg. C. Suttinun; on slide; GBIFCH00763836; VMCMU. Paratypes. 2 larvae; same data as holotype; on slides; GBIFCH00980859, GBIFCH01221814; MZL • 1 larva; Tak Prov., Mueang Distr., Klong Lan Sang; 16°46'53"N, 99°01'16"E; 253 m; 25.xii.2017; leg. C. Suttinun; on slide; GBIFCH00592515; VMCMU.

Larva. Following combination of characters differentiate L. karen sp. nov. from other species of the group sumigarensis: thorax dorsally ochre, with dark brown distolateral dots on mesonotum; abdomen dorsally dark reddish-brown, paler in middle area, segment I ochre; femur with dark brown, triangular marking at inner, distomedial margin; tibia dark brown in subdistal area; scapus and pedicellus laterally with dark brown hypodermal colouration; labial palp segment III subrectangular with inner distal margin concave; paraproct distally not expanded.

Larva (Figs 20–22). Body length 3.5–4.7 mm. Caudalii ~1/2 body length, paracercus ~0.4× body length. Antenna: ~2× as long as head length.

Figure 20. 

Labiobaetis karen sp. nov., larva: a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal view. Scale bars: 1 mm (a, b); 100 µm (c).

Figure 21. 

Labiobaetis karen sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Labial palp; e. Hypopharynx and superlinguae; f. Maxilla; g. Maxillary palp; h. Left mandible; i. Right mandible. Scale bars: 20 µm (c, e, f, h, i); 10 µm (a, b, d, g).

Figure 22. 

Labiobaetis karen sp. nov., larva morphology: a. Fore leg; b. Outer margin of fore femur; c. Inner margin of fore femur; d. Section of fore tibia; e. Fore claw; f, g. Tergalius III; h. Posterior margins of abdominal terga; i. Paraproct; j. Antennal base. Scale bars: 50 µm (a); 20 µm (f); 10 µm (b–e, g–j).

Colouration (Fig. 20a–c). Head and thorax dorsally ochre, head and pronotum with dark brown markings, mesonotum with pronounced dark brown distolateral dots as in Fig. 20a; abdomen dorsally dark reddish-brown, paler in middle area, laterally pale brown, segment I ochre. Fore protoptera ochre. Head, thorax and abdomen ventrally mainly beige, abdominal segments laterally dark reddish brown. Legs pale brown, femur with dark brown, triangular marking at inner, distomedial margin, dark brown streak at outer margin, and dark brown marking at apex; tibia dark brown in subdistal area. Caudalii pale brown. Antennal scapus and pedicellus with dark brown hypodermal, lateral colouration.

Antenna (Fig. 22j) with scape and pedicel sub cylindrical, distolateral process at scape absent.

Labrum (Fig. 21a, b). Sub-rectangular, length 0.7× maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; submarginal arc of ~15 long, clavate setae on each side. Ventrally with marginal row of setae composed of anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 21i). Incisor and kinetodontium fused. Incisor with five denticles; kinetodontium with three denticles, inner margin of innermost denticle with row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola almost straight. Tuft of setae on proximal corner of mola present.

Left mandible (Fig. 21h). Incisor and kinetodontium fused. Incisor with five denticles, kinetodontium with four denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola straight. Tuft of setae on proximal corner of mola absent.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 21e). Lingua approx. as long as superlinguae. Lingua longer than broad, subdistally slightly expanded; medial tuft of stout setae well developed. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 21f, g). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and four or five medium to long simple setae. Maxillary palp longer than length of galea-lacinia; 2-segmented; palp segment II slightly longer than segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment with distolateral excavation, apically rounded.

Labium (Fig. 21c, d). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ~7 robust, spine-like setae, distalmost seta longer; apex with two long and one medium, robust, apically pectinate setae; outer margin with ~3 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and three or four medium, simple setae in anteromedial area; dorsally with four long, spine-like setae near inner margin. Labial palp with segment I approx. as long as segments II and III combined. Segment II with rounded, thumb-like, distomedial protuberance; distomedial protuberance 0.7× width of base of segment III; dorsally with two spine-like setae near outer margin. Segment III subrectangular, inner distal margin slightly concave; length approx. as maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera absent.

Legs (Fig. 22a–e). Ratio of foreleg segments 1.2:1.0:0.5:0.2, middle leg 1.1:1.0:0.4:0.2, hind leg 1.2:1.0:0.4:0.2. Femur. Femur length ~3.5× maximum width. Outer margin with row of 10–12 spine-like setae; length of setae ~0.19× maximum width of femur. Apex rounded, with pair of spine-like setae and short, stout, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch absent on fore and middle legs, rudimentary on hind leg. Tibia. Outer margin with row of short, stout, apically blunt setae, distalmost seta larger. Inner margin with two rows of medium spine-like setae; on apex tuft of fine, simple setae. Patella-tibial suture present on basal 1/3. Tarsus. Outer margin almost bare. Inner margin with row of curved, spine-like setae increasing in length distally. Claw with one row of 9–12 denticles; distally pointed.

Abdominal terga (Fig. 22h). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I smooth, without spines, II–IX with triangular, pointed spines, becoming longer and sharper toward end of abdomen.

Abdominal sterna . Posterior margin of sterna: I–VI smooth, without spines; VII–IX with triangular spines.

Tergalii (Fig. 22f, g). Present on segments II–VII. Margin with small denticles intercalating fine, simple setae. Tracheae partly extending from main trunk to inner and outer margins. Tergalius IV somewhat longer than segments V; tergalius VII as long as segment VIII.

Paraproct (Fig. 22i). Distally not expanded, with ~32 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

Unknown.

The species is dedicated to the indigenous Karen people in Thailand.

Thailand (Fig. 32d).

Holotype. Thailand • larva; Tak Prov., Mueang Distr., Klong Lan Sang; 16°46'53"N, 99°01'16"E; 253 m; 25.xii.2017; leg. C. Suttinun; on slide; GBIFCH01223075; VMCMU. Paratypes. 18 larvae; same data as holotype; 2 on slides; GBIFCH01223076, GBIFCH01221815 (legs); MZL; 16 in alcohol; GBIFCH00829292; GBIFCH00763850; MZL; GBIFCH00763838; VMCMU • 5 larvae; Kanchanaburi Prov., Thong Pha Phum Distr., Pra Chum Mai; 14°34'58"N, 98°34'52"E; 269 m; 25.v.2017; leg. C. Suttinun; 1 on slide; GBIFCH00596155; MZL; 4 in alcohol; GBIFCH00763825; VMCMU • 1 larva; Loei Prov., Wang Saphung Distr., Nam Thob; 17°15'37"N, 101°34'53"E; 376 m; 17.xii.2018; leg. C. Suttinun; on slide; GBIFCH01223086; VMCMU • 4 larvae; Loei Prov., Wang Saphung Distr., Ban Nam Thob; 17°16'11"N, 101°35'51"E; 318 m; 17.xii.2018; leg. C. Suttinun; 1 on slide; GBIFCH00829294 (legs, abdomen); MZL; 3 in alcohol; GBIFCH00763837; MZL • 1 larva; Chiang Mai Prov., Mae On Distr., Huai Teen Tok; 18°52'03"N, 99°19'19"E; 760 m; 21.xi.2018; leg. C. Suttinun; on slide; GBIFCH00607173; VMCMU • 1 larva; Chiang Mai Prov., Chiang Dao Distr., Huai Mae Mae; 19°19'19"N, 98°52'51"E; 809 m; 20.xi.2018; leg. C. Suttinun; on slide; GBIFCH01221823; MZL.

Thailand • 11 larvae; Tak Prov., Mueang Distr., Klong Lan Sang; 16°46'53"N, 99°01'16"E; 253 m; 25.xii.2017; leg. C. Suttinun; 3 on slides; GBIFCH00607174; VMCMU; GBIFCH00975857, GBIFCH00975858; MZL; 8 in alcohol; GBIFCH00763818, GBIFCH00975856, GBIFCH00763830; VMCMU • 5 larvae; Tak Prov., Mueang Distr., Tha Le; 16°44'28"N, 99°02'43"E; 327 m; 26.xii.2017; leg. C. Suttinun; 1 on slide; GBIFCH01221817; MZL; 4 in alcohol; GBIFCH00980863; MZL; GBIFCH00763841; VMCMU • 4 larvae; Chang Mai Prov., Mae On Distr., Huai Teen Tok; 18°52'03''N, 99°19'19''E; 760 m; 17.xi.2023; leg. C. Suttinun; VMCMU.

Larva. Following combination of characters differentiate L. septem sp. nov. from other species of the group sumigarensis: tergalii present on abdominal segments I–VII; abdomen dorsally uniform brown, or brown with crown-like pattern; femur with 9–15 spine-like setae at outer margin; tibia with row of short, apically rounded setae at outer margin, or bare with one medium, apically rounded seta distally; claw with 10–14 denticles.

Larva (Figs 23–26). Body length 3.6–4.6 mm. Cerci ~1/2 body length, paracercus ~1/3 body length. Antenna: ~2× as long as head length.

Figure 23. 

Labiobaetis septem sp. nov., larva (morphotype A): a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal view. Scale bars: 1 mm (a, b); 100 µm (c).

Figure 24. 

Labiobaetis septem sp. nov., larva (morphotype B): a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal view. Scale bars: 1 mm (a, b); 100 µm (c).

Figure 25. 

Labiobaetis septem sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Hypopharynx and superlinguae; e. Maxilla; f. Maxillary palp; g. Left mandible; h. Right mandible. Scale bars: 20 µm (c, e, g, h); 10 µm (a, b, d, f).

Figure 26. 

Labiobaetis septem sp. nov., larva morphology: a. Fore leg (morphotype A); b. Fore leg (morphotype B); c. Section of fore femur (morphotype A); d. Section of fore tibia (morphotype A); e. Outer margin of tibia (morphotype B); f. Inner margin of fore tibia (morphotype B); g. Fore tarsus and claw. Scale bars: 50 µm (a, b); 10 µm (c–g).

Colouration (Figs 23a–c, 24a–c). Head and thorax dorsally yellow-brown with dark grey pattern as in Fig. 23a; abdomen dorsally rather uniform brown, or brown with crown-like pattern. Fore protoptera yellow-brown to brown. Head, thorax and abdomen ventrally mainly pale grey to yellowish, abdominal segments laterally darker, and off-white along margins, abdominal segment IX darker. Legs with femur off-white to grey, with triangular, dark grey, distomedial marking at inner margin and dark grey apex; tibia yellow-brown in basal 1/2 and grey in distal 1/2; tarsus grey. Caudalii grey-brown, with dark brown distomedial section. Antennal scapus and pedicellus laterally dark grey-brown.

Antenna (Fig. 26e) with scape and pedicel sub cylindrical, distolateral process at scape absent.

Labrum (Fig. 25a, b). Sub-rectangular, length 0.7× maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; submarginal arc of ~17 long, clavate setae on each side. Ventrally with marginal row of setae composed of anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 25h). Incisor and kinetodontium fused. Incisor with five denticles; kinetodontium with three denticles, inner margin of innermost denticle with row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola almost straight, with few minute denticles. Tuft of setae on proximal corner of mola present.

Left mandible (Fig. 25g). Incisor and kinetodontium fused. Incisor with five denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola straight, with minute denticles towards subtriangular process. Tuft of setae on proximal corner of mola absent.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 25d). Lingua approx. as long as superlinguae, longer than broad, subdistally slightly expanded; medial tuft of stout setae well developed. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 25e, f). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta three medium to long, simple setae. Maxillary palp longer than length of galea-lacinia; 2-segmented; palp segment II 1.3× length of segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment with well-developed distolateral excavation, apically rounded.

Labium (Fig. 25c). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ~5 spine-like setae; apex with two long and one medium, robust, apically pectinate setae; outer margin with ~5 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and three medium, simple setae in anteromedial area; dorsally with three long, spine-like setae near inner margin. Labial palp with segment I 0.8× length of segments II and III combined. Segment II with rounded, thumb-like, distomedial protuberance; distomedial protuberance 0.8× width of base of segment III; dorsally with two or three spine-like setae near outer margin. Segment III subrectangular; length ~1.2× maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera absent.

Legs (Fig. 26a–g). Ratio of foreleg segments 1.2:1.0:0.4–0.6:0.2, middle leg 1.1:1.0:0.4:0.1, hind leg 1.2:1.0:0.5–0.6:0.2. Femur. Femur length ~4× maximum width. Outer margin with row of 9–15 spine-like setae; length of setae ~0.24× maximum width of femur. Apex rounded, with pair of spine-like setae and some short, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch rudimentary on foreleg, absent on middle and hind leg. Tibia. Outer margin with row of short, stout, apically blunt setae, distalmost seta larger, or bare with one stout, apically rounded seta distally. Inner margin with two rows of medium spine-like setae; on apex tuft of fine, simple setae. Patella-tibial suture present on basal 1/3. Tarsus. Outer margin almost bare. Inner margin with row of curved, spine-like setae. Claw with one row of 10–14 denticles; distally pointed.

Abdominal terga (Fig. 27a). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I–IX with triangular spines, I wide and short, II–IX becoming longer and sharper toward end of abdomen.

Figure 27. 

Labiobaetis septem sp. nov., larva morphology: a. Posterior margins of abdominal terga; b, c. Tergalius III; d. Paraproct; e. Antennal base. Scale bars: 20 µm (b); 10 µm (a, c–e).

Abdominal sterna . Posterior margin of sterna: I–VI smooth, without spines; VII–IX with triangular spines.

Tergalii (Fig. 27b, c). Present on segments I–VII. Margin with small denticles intercalating fine, simple setae. Tracheae partly extending from main trunk to inner and outer margins. Tergalius I small, ~1/3 length of segment II; tergalius IV somewhat longer than segment V; tergalius VII as long as segment VIII.

Paraproct (Fig. 27d). Distally not expanded, with ~29 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

The species appears with two different morphotypes, which partly share the same locations: based on our material, morphotype A is characterised by a dorsally rather uniform brown abdomen, a row of setae at outer margin of tibia, 10–15 setae at outer margin of femur, and a claw with 10 or 11 denticles; morphotype B has a crown-like pattern dorsally on the abdomen, outer margin of tibia almost bare, femur with nine or ten setae at outer margin, and claw with 12–14 denticles (see in discussion section). Holotype and paratypes correspond with morphotype A, specimens with morphotype B are mentioned as other material.

Unknown.

The Latin word septem, meaning seven, refers to the seven pairs of tergalii of this species. All other known species of the group sumigarensis have only six pairs of tergalii.

Thailand (Fig. 32d).

Holotype. Thailand • larva; Ranong Prov., Mueang Distr., Huai Nam Sai; 09°43'25"N, 98°36'29"E; 50 m; 20.vi.2018; leg. C. Suttinun; on slide; GBIFCH00980864; VMCMU. Paratypes. Thailand • 4 larvae; Ranong Prov., Mueang Distr., Punyaban Waterfall; 10°03'54"N, 98°40'13"E; 52 m; 19.vi.2018; leg. C. Suttinun; 1 on slide; GBIFCH01223077; MZL; 3 in alcohol; GBIFCH00763828; VMCMU • 14 larvae; Ranong Prov., Mueang Distr., Huai Por Ta Hin Rao; 09°52'08"N, 98°37'32"E; 20 m; 20.vi.2018; leg. C. Suttinun; 1 on slide; GBIFCH00980860; MZL; 13 in alcohol; GBIFCH00763826, GBIFCH00763834; VMCMU; GBIFCH00975850; MZL • 1 larva; Ranong Prov., Mueang Distr., Klong Nok Ngang; 09°42'22"N, 98°34'39"E; 11 m; 21.vi.2018; leg. C. Suttinun; on slide; GBIFCH00975861; MZL • 5 larvae; Ranong Prov., Mueang Distr., Huai Por Ta; 10°02'03"N, 98°39'29"E; 22 m; 19.iv.2018; leg. C. Suttinun; in alcohol; GBIFCH00763835; VMCMU.

Larva. Following combination of characters differentiate L. ranongensis sp. nov. from other species of the group sumigarensis: abdomen dorsally yellow-brown, basal parts of terga paler, posterior parts with a darker, slightly crown-like marking; labial palp segment III subrectangular, segment II with thumb-like protuberance with straight distal margin and rounded lateral margin; maxillary palp longer than galea-lacinia, terminal segment with well-developed, distolateral excavation; left mandible with margin between prostheca and mola straight, with minute marginal and submarginal denticles; abdominal tergites II–IX with triangular, sharply pointed spines on posterior margins; paraproct distally not expanded, with ~28 spines.

Larva (Figs 28–30). Body length 3.3–4.9 mm. Cerci ~1/2 body length, paracercus ~0.4× body length. Antenna: ~2× as long as head length.

Figure 28. 

Labiobaetis ranongensis sp. nov., larva: a. Habitus, dorsal view; b. Habitus, ventral view; c. Abdomen, dorsal view. Scale bars: 1 mm (a, b); 100 µm (c).

Figure 29. 

Labiobaetis ranongensis sp. nov., larva morphology: a. Labrum; b. Section of labrum, dorsal focus; c. Labium; d. Labial palp; e. Hypopharynx and superlinguae; f. Maxilla; g. Maxillary palp; h. Left mandible; i. Right mandible. Scale bars: 20 µm (c, e, f, h, i); 10 µm (a, b, d, g).

Figure 30. 

Labiobaetis ranongensis sp. nov., larva morphology: a. Hind leg; b. Section of hind femur; c. Section of hind tibia; d. Hind tarsus and claw; e. Antennal base; f. Posterior margins of abdominal terga; g. Posterior margins of abdominal segment IX; h. Paraprocts; i, j. Tergalius V. Scale bars: 50 µm (a); 20 µm (g); 10 µm (b–f, h–j).

Colouration (Fig. 28a–c). Head and thorax dorsally yellow-brown, with dark brown markings; abdomen dorsally yellow-brown, anterior parts of abdominal segments paler, posterior parts with a darker, slightly crown-like marking; Fore protoptera yellow-brown. Thorax ventrally off-white; abdomen ventrally pale grey-brown. Legs with femur off-white, with distomedial, triangular grey-brown marking, apex grey-brown; tibia and tarsus yellow-brown. Caudalii yellow-brown.

Antenna (Fig. 30e) with scape and pedicel sub cylindrical, distolateral process at scape absent.

Labrum (Fig. 29a, b). Sub-rectangular, length 0.7× maximum width. Distal margin with medial emargination and small process. Dorsally with medium, fine, simple setae scattered over surface; submarginal arc of ~18 long, clavate setae on each side. Ventrally with marginal row of setae composed of anterolateral long, feathered setae and medial long, bifid setae.

Right mandible (Fig. 29i). Incisor and kinetodontium fused. Incisor with five denticles; kinetodontium with three denticles, inner margin of innermost denticle with row of thin setae. Prostheca robust, apically denticulate. Margin between prostheca and mola slightly convex, with minute denticles. Tuft of setae on proximal corner of mola present.

Left mandible (Fig. 29h). Incisor and kinetodontium fused. Incisor with five denticles, kinetodontium with three denticles. Prostheca robust, apicolaterally with small denticles and comb-shaped structure. Margin between prostheca and mola straight, with marginal and submarginal, minute denticles. Tuft of setae on proximal corner of mola absent.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 29e). Lingua longer than superlinguae, longer than broad, subdistally slightly expanded; medial tuft of stout setae well developed. Superlinguae with lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 29f, g). Galea-lacinia ventrally with two simple, apical setae below canines. Medially with one feathered, spine-like seta and three medium to long, simple setae. Maxillary palp longer than length of galea-lacinia; 2-segmented; palp segment II ~1.2× length of segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment with well-developed distolateral excavation, apically rounded.

Labium (Fig. 29c, d). Glossa basally broad, narrowing toward apex; shorter than paraglossa; inner margin with ~7 robust, spine-like setae, increasing in length distally; apex with two long and one medium, robust, apically pectinate setae; outer margin with ~4 spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, slightly curved inward; apex rounded; with three rows of long, robust, distally pectinate setae in apical area and four medium, simple setae in anteromedial area; dorsally with three or four long, spine-like setae near inner margin. Labial palp with segment I approx. as long as segments II and III combined. Segment II with thumb-like protuberance with straight distal margin and rounded lateral margin; distomedial protuberance ~0.9× width of base of segment III; dorsally with two spine-like setae near outer margin. Segment III subrectangular; length approx. as maximal width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae. Mentum distally with dark grey-brown marking.

Hind protoptera absent.

Legs (Fig. 30a–d). Ratio of foreleg segments 1.1:1.0:0.4:0.1, middle leg 1.1:1.0:0.4:0.1, hind leg 1.2:1.0:0.4:0.1. Femur. Femur length ~3.7× maximum width. Outer margin with row of 9–15 spine-like setae; length of setae ~0.30× maximum width of femur. Apex rounded, with pair of spine-like setae and usually few short, apically blunt setae. Stout, lanceolate, pointed setae scattered along inner margin; femoral patch absent on fore and middle legs, rudimentary on hind leg. Tibia. Outer margin with row of short, apically blunt setae, distalmost seta larger. Inner margin with two rows of medium spine-like setae; on apex tuft of fine, simple setae. Patella-tibial suture present on basal 1/3. Tarsus. Outer margin almost bare. Inner margin with row of curved, spine-like setae. Claw with one row of 7–14 denticles; distally pointed.

Abdominal terga (Fig. 30f, g). Surface with irregular rows of U-shaped scale bases and fine, simple, scattered setae. Posterior margin of terga: I smooth, without spines, II–IX with triangular, sharply pointed spines, becoming longer, narrower and sharper toward end of abdomen.

Abdominal sterna (Fig. 30g). Posterior margin of sterna: I–VI smooth, without spines; VII–IX with triangular spines, spines on segment IX not continuous.

Tergalii (Fig. 30i, j). Present on segments II–VII. Margin with small denticles intercalating fine, simple setae. Tracheae partly extending from main trunk to inner and outer margins. Tergalius IV somewhat longer than segment V; tergalius VII as long as 3/4 length of segment VIII.

Paraproct (Fig. 30h). Distally not expanded, with ~30 stout, marginal spines. Surface scattered with U-shaped scale bases and fine, simple setae. Cercotractor with numerous small, marginal spines.

Unknown.

The species name refers to Ranong Prov., where the type locality is located.

Thailand (Fig. 32d).