Labiobaetis mon sp. nov.

Figs 1 a – c, 2, 3

Type material.

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; GBIFCH 00980857; VMCMU . Paratypes. 40 larvae; same data as holotype; 21 in alcohol; GBIFCH 00980854, GBIFCH 00763852; MZL; 19 in alcohol; GBIFCH 00763797; 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; GBIFCH 00592518; MZL; 9 in alcohol; GBIFCH 00763808; 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; GBIFCH 00980852; 34 in alcohol; GBIFCH 00763799; 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; GBIFCH 00607177; 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; GBIFCH 00829296; MZL .

Other material.

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; GBIFCH 01556160; VMCMU .

Diagnosis.

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.

Description.

Larva (Figs 1 a – 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.

Colouration (Fig. 1 a – c). Head and thorax head dorsally mostly dark brown with indistinct pattern as in Fig. 1 a. 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. 3 e) with scape and pedicel sub cylindrical, distolateral process at scape well developed.

Labrum (Fig. 2 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 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. 2 i). 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. 2 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 present.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 2 e). 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. 2 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 rounded.

Labium (Fig. 2 c, 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. 3 k) present, well developed.

Legs (Fig. 3 a – 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. 3 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.

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

Tergalii (Fig. 3 i, 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. 3 h). 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.

Imago.

Unknown.

Etymology.

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

Distribution.

Thailand (Fig. 32 a).