Labiobaetis lahu, Kaltenbach & Gattolliat & Boonsoong & Suttinun, 2025

Kaltenbach, Thomas, Gattolliat, Jean-Luc, Boonsoong, Boonsatien & Suttinun, Chanaporn, 2025, New species of Labiobaetis Novikova & Kluge from Thailand (Ephemeroptera, Baetidae), ZooKeys 1258, pp. 213-276 : 213-276

Labiobaetis lahu sp. nov.

Figs 4 , 5 , 6

Type material.

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; GBIFCH 00596154 ; VMCMU . Paratypes. 2 larvae; same data as holotype; on slides; GBIFCH 01223072 , GBIFCH 01223073 ; 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; GBIFCH 01223071 ; 1 in alcohol; GBIFCH 00763789 ; 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; GBIFCH 00607175 ; 7 in alcohol; GBIFCH 00763787 , GBIFCH 00763790 ; 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; GBIFCH 00607176 ; MZL; 21 in alcohol; GBIFCH 00980856 , GBIFCH 00980858 , GBIFCH 00763791 , GBIFCH 00763786 , GBIFCH 00763871 , GBIFCH 00763874 ; 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; GBIFCH 00829295 , GBIFCH 00763785 , GBIFCH 00763788 ; VMCMU; GBIFCH 00763851 , GBIFCH 00763873 ; 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; GBIFCH 00980851 , GBIFCH 00763807 ; VMCMU .

Diagnosis.

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. 4 a , especially yellowish oval markings on terga III and V; legs with reddish-brown spot distally on femur; hind protoptera present, well developed.

Description.

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.

Colouration (Fig. 4 a – c ). Thorax and abdomen dorsally dark grey with distinct yellowish markings as in Fig. 1 a ; 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. 6 i ) with scape and pedicel sub cylindrical, distolateral process at scape well developed.

Labrum (Fig. 5 a, 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. 5 i ). 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. 5 h ). 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. 5 e ). 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. 5 f, 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. 5 c, 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. 6 e ) present, well developed.

Legs (Fig. 6 a – 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. 6 f, 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. 6 j, 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. 6 h ). 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.

Imago.

Unknown.

Etymology.

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

Distribution.

Thailand (Fig. 32 a ).

Figures

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).

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).

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).

Figure 32. Distribution maps: a. Labiobaetis batakorum species group; b. Labiobaetis numeratus species group; c. Labiobaetis operosus species group; d. Labiobaetis sumigarensis species group.