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

Labiobaetis nisaratae sp. nov.

Figs 16 View Figure 16 , 17 View Figure 17 , 18 View Figure 18 , 19 View Figure 19

Type-material.

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; GBIFCH 01221811 ; VMCMU GoogleMaps . Paratypes. 9 larvae, 1 male imago (reared from larva); same data as holotype; 2 larvae on slides; GBIFCH 00592508 , GBIFCH 00592509 ; MZL; 7 larvae in alcohol; GBIFCH 00975862 ; VMCMU; 1 imago in alcohol; VMCMU GoogleMaps • 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; GBIFCH 01223084 ; MZL GoogleMaps .

Diagnosis.

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. 16 a, b, d View Figure 16 , 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.

Description.

Larva (Figs 16 View Figure 16 – 18 View Figure 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.

Colouration (Fig. 16 a – d View Figure 16 ). 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. 18 g View Figure 18 ) with scape and pedicel sub cylindrical, distolateral process at scape well developed.

Labrum (Fig. 17 a, b View Figure 17 ). 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. 17 i View Figure 17 ). 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. 17 h View Figure 17 ). 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. 17 e View Figure 17 ). 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. 17 f, g View Figure 17 ). 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. 17 c, d View Figure 17 ). 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. 19 g View Figure 19 ) well developed.

Legs (Fig. 18 a – f View Figure 18 ). 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. 18 k View Figure 18 ). 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. 18 h – j View Figure 18 ). 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. 18 l View Figure 18 ). 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. 19 a – f View Figure 19 ). 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.

Comparison.

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.

Etymology.

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.

Distribution.

Thailand (Fig. 32 c View Figure 32 ).