Labiobaetis tonsator, 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 tonsator sp. nov.

Figs 13 , 14 , 15

Type material.

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; GBIFCH 00829272 ; VMCMU . Paratype. 1 larva; same data as holotype; on slide; GBIFCH 00763863 ; MZL .

Diagnosis.

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.

Description.

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

Colouration (Fig. 13 a – c ). Head and thorax dorsally yellow-grey with grey markings as in Fig. 13 a , 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. 15 k ) with scape and pedicel sub cylindrical, distolateral process at scape absent.

Labrum (Fig. 14 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 ~ 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. 14 i ). 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. 14 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. Tuft of setae on proximal corner of mola present.

Both mandibles with lateral margins almost straight.

Hypopharynx and superlinguae (Fig. 14 e ). 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. 14 f, 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. 14 c, 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. 15 a – 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. 15 e ). 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. 15 h, 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. 15 j ). 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.

Imago.

Unknown.

Etymology.

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

Distribution.

Thailand (Fig. 32 b ).

Figures

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).

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