New species of Labiobaetis Novikova & Kluge from Thailand (Ephemeroptera, Baetidae)
Abstract
Investigations of material collected by one of us (CS) between May 2017 and November 2023 from 70 localities in Thailand further increases our knowledge of the diversity of the genus Labiobaetis Novikova & Kluge, 1987 in Thailand and Southeast Asia in general. Eleven species have been identified using a combination of morphological and molecular analysis (COI). Nine are new to science, they are described and illustrated based on their larvae, and in one case, complemented by the male imago. Two of the new species belong to the L. batakorum species group, L. mon sp. nov., L. lahu sp. nov.; three to the L. numeratus species group, L. tenasserimensis sp. nov., L. angularis sp. nov., L. tonsator sp. nov.; one to the L. operosus species group, L. nisaratae sp. nov., and three to the L. sumigarensis species group, L. karen sp. nov., L. septem sp. nov., L. ranongensis sp. nov. A key to all species of Labiobaetis from continental Southeast Asia is provided. Additionally, the genetic distances (COI; Kimura-2 parameter) including all species treated in this study are discussed. The total number of Labiobaetis species worldwide is augmented to approximately 170.
Full text
213 New species of Labiobaetis Novikova & Kluge from Thailand (Ephemeroptera, Baetidae) Thomas Kaltenbach1,2 , Jean-Luc Gattolliat1,2 , Boonsatien Boonsoong3,4 , Chanaporn Suttinun5 1 Naturéum, Muséum cantonal des Sciences Naturelles, Département de zoologie, Palais de Rumine, Place Riponne 6, CH-1005 Lausanne, Switzerland 2 Department of Ecology and Evolution, University of Lausanne (UNIL), CH-1015 Lausanne, Switzerland 3 Department of Zoology, Faculty of Science, Kasetsart University, Bangkok, Thailand 4 Biodiversity Center Kasetsart University (BDCKU), Bangkok, Thailand 5 Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand Corresponding author: Chanaporn Suttinun ([email protected]) Copyright: © Thomas Kaltenbach et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0). Research Article Abstract Investigations of material collected by one of us (CS) between May 2017 and November 2023 from 70 localities in Thailand further increases our knowledge of the diversity of the genus Labiobaetis Novikova & Kluge, 1987 in Thailand and Southeast Asia in general. Eleven species have been identified using a combination of morphological and molecular analysis (COI). Nine are new to science, they are described and illustrated based on their larvae, and in one case, complemented by the male imago. Two of the new species belong to the L. batakorum species group, L. mon sp. nov., L. lahu sp. nov.; three to the L. numeratus species group, L. tenasserimensis sp. nov., L. angularis sp. nov., L. tonsator sp. nov.; one to the L. operosus species group, L. nisaratae sp. nov., and three to the L. sumigarensis species group, L. karen sp. nov., L. septem sp. nov., L. ranongensis sp. nov. A key to all species of Labiobaetis from continental Southeast Asia is provided. Additionally, the genetic distances (COI; Kimura-2 parameter) including all species treated in this study are discussed. The total number of Labiobaetis species worldwide is augmented to approximately 170. Key words: COI, integrative taxonomy, mayflies, morphology, Southeast Asia Introduction Southeast Asia is one of the regions with the highest biodiversity worldwide in general, and also specifically for mayflies. Considerable effort has been made in recent years to gain a better understanding of this yet understudied fauna, including studies focusing on the lesser known, but highly diverse mayfly family Baetidae. Particular emphasis was placed especially on Thailand, but also on the archipelagos of Indonesia and the Philippines, where new genera of Baetidae and many new species were discovered (e.g. Gattolliat 2012; Kaltenbach and Gattolliat 2019a, b, 2020, 2021; Kaltenbach et al. 2020b, 2021, 2022a, b, 2023a; Kluge 2020a, 2020b, 2022; studies on Thailand cited below). Thailand is located near the epicentre between China, the Indian subcontinent, and Southeast Asian islands. It is well-known for its geographical and ecological diversity, ranging from mountainous regions in the north to lowland floodplains in the centre, Academic editor: Ben Price Received: 25 July 2025 Accepted: 25 September 2025 Published: 6 November 2025 ZooBank: https://zoobank. org/391169F4-D998-434F-A0514A0E4830D548 Citation: Kaltenbach T, Gattolliat J-L, Boonsoong B, Suttinun C (2025) New species of Labiobaetis Novikova & Kluge from Thailand (Ephemeroptera, Baetidae). ZooKeys 1258: 213–276. https://doi.org/10.3897/ zookeys.1258.166681 ZooKeys 1258: 213–276 (2025) DOI: 10.3897/zookeys.1258.166681
214 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand plateau areas shaped by tectonic processes in the northeastern and extensive coastal regions in the south. Thailand’s complex topography combined with its tropical climate gives rise to a wide variety of lotic habitats such as ri vers and headwater streams, some of which are unique habitats (e.g. headwater streams on a limestone mountain range) (Ridd et al. 2011). Notably, they support an exceptionally diverse assemblage of mayflies especially in the family Baetidae. Over the last decade, two new genera and 17 new species were reported from Thailand (Kluge and Novikova 2017; Kluge et al. 2020; Kluge and Suttinun 2020; Sutthinun et al. 2018; Suttinun et al. 2020, 2021, 2022; Phlai-ngam et al. 2022a, b, 2024; Tungpairojwong et al. 2022; Bespalaya et al. 2023; Kaltenbach et al. 2023a). The high levels of endemism and species richness fostered by the complexity of these ecosystems, and influenced by both natural and man-made causes, make Thailand a key region for the study and conservation of freshwater biodiversity. Further collection efforts and studies are ongoing. The genus Labiobaetis Novikova & Kluge, 1987 belongs to Baetidae, the most diverse family of Ephemeroptera. More than one fourth of all mayfly species worldwide (> 1200 species) are part of Baetidae (Sartori and Brittain 2015; Jacobus et al. 2019; updated by the authors). Labiobaetis is the richest genus of Baetidae, and one of the richest amongst mayflies in general, with ~160 previously described species (Lugo-Ortiz et al. 1999; Barber-James et al. 2013, Kaltenbach and Gattolliat 2018, 2019b, 2020, 2021 and citations therein; Kaltenbach et al. 2020a, 2022a and citations therein, 2023b; Sivaruban et al. 2022; Pandiaran et al. 2025). The distribution of Labiobaetis is nearly worldwide, except for the Neotropical realm, New Zealand, New Caledonia, and some remote islands. The history and concept of Labiobaetis were summarised in detail by Shi and Tong (2014) and Kaltenbach and Gattolliat (2018). Recently, a comprehensive study on the Baetidae of Thailand was conducted by Suttinun (2021). Specimens were collected from 2017 to 2023 in 11 provinces and 70 localities mainly in Western and Southern Thailand, and a few in Northern, Northeastern, and Eastern Thailand. Among many other genera of Baetidae, Labiobaetis was also treated in this study, without formerly describing and naming the new species. This contribution is based on the Labiobaetis material collected during this study (Suttinun 2021), and focuses on the formal taxonomic treatment, including the description of nine new species. Given the extraordinary diversity in Thailand and despite the strong effort already done so far, it is reasonable to anticipate the discovery of numerous additional species through future studies in Thailand and in surrounding countries. Materials and methods All specimens were preserved in 70%–96% ethanol. The dissection of larvae was done in Cellosolve (2-Ethoxyethanol) with subsequent mounting on slides with Euparal liquid, using an Olympus SZX7 stereomicroscope. Photographs of larvae were taken using a Canon EOS 6D camera and processed with the programs Adobe Photoshop Lightroom (http://www.adobe. com) and Helicon Focus v. 5.3 (http://www.heliconsoft.com). Photographs of larval parts on slides were taken with an Olympus BX43 microscope equipped with an Olympus SC 50 camera and the program Olympus CellSense v. 4.1. All photographs were subsequently enhanced with Adobe Photoshop Elements 13.
215 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand The DNA of part of the specimens was extracted using non-destructive methods allowing subsequent morphological analysis (see Vuataz et al. 2011 for details). We amplified a 658 bp fragment of the mitochondrial gene cytochrome oxidase subunit 1 (COI) using the primers LCO 1490 and HCO 2198 (Folmer et al. 1994). Sequencing was done with Sanger’s method (Sanger et al. 1977). The genetic variability between specimens was estimated using Kimura-2-parameter distances (K2P; Kimura 1980), calculated with the program MEGA 11 (Tamura et al. 2021; http://www.megasoftware.net). The GenBank accession numbers are given in Table 1; nomenclature of gene sequences follows Chakrabarty et al. (2013). The distribution maps were generated with the program SimpleMappr (https://simplemappr.net, Shorthouse 2010). The dichotomous key was elaborated with the support of the program DKey v. 1.3.0 (http://drawwing.org/dkey, Tofilski 2018). The terminology follows Kluge (2004) and Kluge (2005) (term “protopteron”). Abbreviations MZL Naturéum, Muséum des Sciences Naturelles, Lausanne (Switzerland) VMCMU Insect section of the Veterinary Anatomy and Pathology Museum Chiang Mai University, Chiang Mai (Thailand) Table 1. Sequenced specimens. Species Specimen voucher Specimen voucher GPS coordinates GenBank GenSeq catalogue # catalogue # (slide) # (COI) Nomenclature L. multus (Sumatra) GBIFCH00235847 – 00°34'25"S, 100°43'54"E MN167323 genseq-4 COI L. multus GBIFCH00829311 GBIFCH01556161 07°34'32"N, 99°47'13"E PX067793 genseq-4 COI GBIFCH00980855 – 07°29'33"N, 99°46'26"E PX067795 genseq-4 COI GBIFCH00980853 – 07°43'44"N, 99°44'21"E PX067794 genseq-4 COI L. mon sp. nov. GBIFCH00829315 GBIFCH01556160 12°03'50"N, 99°37'39"E PX067748 genseq-2 COI GBIFCH00829307 GBIFCH00592518 13°30'33"N, 99°17'12"E PX067749 genseq-2 COI GBIFCH00980852 – 13°30'57"N, 99°20'40"E PX067746 genseq-2 COI GBIFCH00980854 – 12°58'42"N, 99°34'55"E PX067745 genseq-2 COI GBIFCH00980857 – 12°58'42"N, 99°34'55"E PX067747 genseq-1 COI GBIFCH00829296 – 12°52'36"N, 102°05'48"E PX067744 genseq-2 COI L. lahu sp. nov. GBIFCH00829303 GBIFCH01223071 16°48'16"N, 99°01'19"E PX067750 genseq-2 COI GBIFCH00829301 GBIFCH01223072 16°46'53"N, 99°01'16"E PX067753 genseq-2 COI GBIFCH00829318 GBIFCH01223073 16°46'53"N, 99°01'16"E PX067758 genseq-2 COI GBIFCH00829302 GBIFCH00596154 16°46'53"N, 99°01'16"E PX067754 genseq-1 COI GBIFCH00829298 GBIFCH00607175 17°18'04"N, 101°46'33"E PX067752 genseq-2 COI GBIFCH00829306 GBIFCH00607176 19°17'02"N, 98°58'05"E PX067755 genseq-2 COI GBIFCH00829295 – 16°42'04"N, 98°30'41"E PX067751 genseq-2 COI GBIFCH00980856 – 19°17'02"N, 98°58'05"E PX067757 genseq-2 COI GBIFCH00980858 – 19°17'02"N, 98°58'05"E PX067759 genseq-2 COI GBIFCH00980851 – 13°30'57"N, 99°20'40"E PX067756 genseq-2 COI L. tenasserimensis sp. nov. GBIFCH00829286 – 13°31'27"N, 99°14'39"E PX067774 genseq-2 COI GBIFCH00829275 – 13°31'27"N, 99°14'39"E PX067772 genseq-2 COI GBIFCH00829285 – 09°41'27"N, 98°35'19"E PX067773 genseq-2 COI
216 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand Species Specimen voucher Specimen voucher GPS coordinates GenBank GenSeq catalogue # catalogue # (slide) # (COI) Nomenclature L. angularis sp. nov. GBIFCH00829290 – 12°58'42"N, 99°34'55"E PX067788 genseq-2 COI GBIFCH00829278 – 13°24'22"N, 99°16'44"E PX067779 genseq-2 COI GBIFCH00829279 – 12°58'42"N, 99°34'55"E PX067780 genseq-2 COI GBIFCH00829287 – 12°03'50"N, 99°37'39"E PX067786 genseq-2 COI GBIFCH00829277 – 12°38'14"N, 99°30'59"E PX067777 genseq-2 COI GBIFCH00829280 – 12°46'03"N, 99°34'54"E PX067781 genseq-2 COI GBIFCH00829283 – 13°30'57"N, 99°20'40"E PX067784 genseq-2 COI GBIFCH00829274 – 12°46'03"N, 99°34'54"E PX067778 genseq-2 COI GBIFCH00829284 – 14°34'58"N, 98°34'52"E PX067785 genseq-2 COI GBIFCH00829273 – 09°42'22"N, 98°34'39"E PX067775 genseq-2 COI GBIFCH00829282 – 13°30'33"N, 99°17'12"E PX067783 genseq-2 COI GBIFCH00829289 – 13°28'41"N, 99°14'55"E PX067787 genseq-2 COI GBIFCH00829291 – 13°24'22"N, 99°16'44"E PX067789 genseq-2 COI GBIFCH00829281 – 17°16'11"N, 101°35'51"E PX067782 genseq-2 COI GBIFCH00829276 – 12°52'36"N, 102°05'48"E PX067776 genseq-2 COI L. tonsator sp. nov. GBIFCH00829272 – 07°11'43"N, 100°04'18"E PX067791 genseq-1 COI L. cf. paraoperosus GBIFCH00829310 GBIFCH01223074 10°03'54"N, 98°40'13"E PX067797 genseq-4 COI GBIFCH00829312 GBIFCH00596156 10°03'54"N, 98°40'13"E PX067796 genseq-4 COI L. nisaratae sp. nov. GBIFCH00829316 GBIFCH01223084 14°34'58"N, 98°34'52"E PX067790 genseq-2 COI L. karen sp. nov. GBIFCH00829300 GBIFCH00592515 16°46'53"N, 99°01'16"E PX067760 genseq-2 COI GBIFCH00980859 – 14°34'58"N, 98°34'52"E PX067761 genseq-2 COI L. septem sp. nov. GBIFCH00829297 GBIFCH00596155 14°34'58"N, 98°34'52"E PX067765 genseq-2 COI GBIFCH00829292 GBIFCH01221815 16°46'53"N, 99°01'16"E PX067762 genseq-2 COI GBIFCH00829294 GBIFCH01221816 17°16'11"N, 101°35'51"E PX067763 genseq-2 COI GBIFCH00975856 – 16°46'53"N, 99°01'16"E PX067766 genseq-4 COI GBIFCH00975857 – 16°46'53"N, 99°01'16"E PX067767 genseq-4 COI GBIFCH00975858 – 16°46'53"N, 99°01'16"E PX067768 genseq-4 COI GBIFCH00980863 GBIFCH01221817 16°44'28"N, 99°02'43"E PX067764 genseq-4 COI L. cf. septem sp. nov. GBIFCH00975853 – 19°19'19"N, 98°52'51"E PX067798 genseq-4 COI GBIFCH00975854 – 19°19'19"N, 98°52'51"E PX067799 genseq-4 COI L. ranongensis sp. nov. GBIFCH00980860 – 09°52'08"N, 98°37'32"E PX067769 genseq-2 COI GBIFCH00980864 – 09°43'25"N, 98°36'29"E PX067770 genseq-1 COI GBIFCH00975861 – 09°42'22"N, 98°34'39"E PX067771 genseq-2 COI Taxonomy List of Labiobaetis species from Thailand batakorum group 1. L. multus (Müller-Liebenau, 1984) (new assignment to the group) 2. Labiobaetis mon sp. nov. 3. Labiobaetis lahu sp. nov. numeratus group 4. Labiobaetis tenasserimensis sp. nov. 5. Labiobaetis angularis sp. nov. 6. Labiobaetis tonsator sp. nov. operosus group 7. Labiobaetis cf. paraoperosus Kaltenbach & Gattolliat, 2018 8. Labiobaetis nisaratae sp. nov.
217 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand sumigarensis group 9. Labiobaetis karen sp. nov. 10. Labiobaetis septem sp. nov. 11. Labiobaetis ranongensis sp. nov. Labiobaetis batakorum species group (Kaltenbach and Gattolliat 2019b: 7) Diagnosis. Dorsal surface of labrum with submarginal arc of simple setae, 1st and 2nd setae after submedian seta standing closely together; labial palp segment II with large, lobed distomedial protuberance; left mandible without setae at apex of mola; lingua of hypopharynx with well developed, short medial tuft of setae; distolateral process at scape well developed; paraproct distally not expanded; hind protoptera absent (L. batakorum species group s. str.) or present (L. multus and closely related species L. mon sp. nov. and L. lahu sp. nov.). Probably, the L. multus species group should be included into the L. tricolor species group (Kluge et al. 2023). Here, we keep it separate until adults and eggs of at least one of the species from Southeast Asia are described. The following species are known from continental Southeast Asia: Labiobaetis multus (Müller-Liebenau, 1984) (new assignment to the group), Labiobaetis mon sp. nov., Labiobaetis lahu sp. nov. Labiobaetis multus (Müller-Liebenau, 1984) Fig. 1d Baetis multus Müller-Liebenau, 1984: 263. Labiobaetis multus (Müller-Liebenau): McCafferty and Waltz 1995: 21. Material examined. 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. Diagnosis. 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. Comparison. 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). Distribution. Malaysia (Selangor), Indonesia (Sumatra), Thailand (Fig. 32a).
218 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand Labiobaetis mon sp. nov. https://zoobank.org/80D6424A-DD90-455A-91D0-F8CCF3162AED Figs 1a–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; 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. 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; GBIFCH01556160; 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 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. 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 greybrown 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, 1st and 2nd 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
219 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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). 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.
220 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
221 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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.
228 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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. Imago. Unknown. Etymology. The species is dedicated to the indigenous Lahu people in Thailand. Distribution. Thailand (Fig. 32a). Labiobaetis numeratus species group (Kaltenbach and Gattolliat 2019b: 62) Diagnosis. Dorsal surface of labrum with submarginal row of simple setae, 1st and 2nd setae after submedian seta closely together; labial palp segment II with thumb-like protuberance; right mandible with pronounced hump between prostheca and mola, with thin setae basally at mola; distal margin of left mandible usually convex; maxillary palp segment II longer than segment I, usually bent; antennal scape without distolateral process; superlinguae strongly sclerotised along basal margin; glossae with robust setae along inner margin; vestigial hind protoptera; tergalii on abdominal segments II–VII; outer margin of femur with partial 2nd row of setae in proximal 1/2; tibia ventral margin with much longer seta distally at suture. The following species are known from continental Southeast Asia: Labiobaetis numeratus (Müller-Liebenau, 1984), Labiobaetis tenasserimensis sp. nov., Labiobaetis angularis sp. nov., Labiobaetis tonsator sp. nov. Labiobaetis tenasserimensis sp. nov. https://zoobank.org/4C747AF6-9599-417A-9523-C6D07647170B Figs 7–9 Type material. 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. Diagnosis. 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. Description. 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. 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.
229 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
230 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
231 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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, 1st and 2nd 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 2nd 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
232 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
233 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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. Imago. Unknown. Comparison. 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). Etymology. The species name is derived from the name of the Tenasserim mountain range where it was collected. Distribution. Thailand (Fig. 32b). Labiobaetis angularis sp. nov. https://zoobank.org/63BEC25D-40D6-4803-8B9C-ECC29B29FA5A Figs 10–12 Type material. 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;
234 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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. Diagnosis. 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. Description. 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. 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 greybrown. Head and thorax ventrally mainly grey; abdomen ventrally dark greybrown, 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, 1st and 2nd setae closely together. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid setae.
235 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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). 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.
236 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
237 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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 2nd 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.
244 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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. Diagnosis. 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. Remark. The larva has no morphological difference to L. paraoperosus from Indonesia (Sumatra), but there is a genetic distance of 12% (COI, K2P). Distribution. Thailand (Fig. 32c), but L. paraoperosus is known from Sumatra (Indonesia). Labiobaetis nisaratae sp. nov. https://zoobank.org/B127C952-7BC2-4E0F-83B0-E530784B585C Figs 16–19 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; 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. 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. 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. Description. 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. 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
245 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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). 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
246 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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, spinelike 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. 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.
247 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
248 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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. 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. 32c). Labiobaetis sumigarensis species group (Kaltenbach and Gattolliat 2019b: 30) Diagnosis. Labrum dorsal surface with submarginal row of clavate setae, submedian setae absent; left mandible without setae at mola apex; hind protoptera absent; tergalii usually on abdominal segments II–VII; distolateral process at scape absent or poorly developed; The following species are known from continental Southeast Asia: Labiobaetis diffundus (Müller-Liebenau, 1984), Labiobaetis kui Kaltenbach, Garces & Gattolliat, 2022, Labiobaetis karen sp. nov., Labiobaetis septem sp. nov., Labiobaetis ranongensis sp. nov.
249 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
250 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
251 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand Labiobaetis karen sp. nov. https://zoobank.org/69CDB73A-552B-47BF-AABF-DE24C93FD380 Figs 20–22 Type material. 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. Diagnosis. 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. Description. 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. 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.
252 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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). 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,
253 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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). 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;
260 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
261 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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). 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. Abdominal sterna. Posterior margin of sterna: I–VI smooth, without spines; VII–IX with triangular spines.
262 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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. Remark. 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. Imago. Unknown. Etymology. 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. Distribution. Thailand (Fig. 32d). Labiobaetis ranongensis sp. nov. https://zoobank.org/B38C906E-6CFD-4A16-B283-26BAB4798FCD Figs 28–30 Type material. 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. Diagnosis. 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.
263 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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). Description. 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. 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,
264 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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.
265 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
266 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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).
267 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 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. Imago. Unknown. Etymology. The species name refers to Ranong Prov., where the type locality is located. Distribution. Thailand (Fig. 32d). Key to the Labiobaetis species of continental Southeast Asia (larvae) 1 Labrum dorsally with arc of simple setae ............................................2 – Labrum dorsally with arc of feathered or clavate setae .......................8 2(1) With well-developed hind protoptera (batakorum species group) .......3 – With minute hind protoptera (numeratus species group) .................... 5 3(2) Abdomen dorsally rather uniform brown to dark brown, paler in middle area, tergum V not much brighter (Fig. 1a) ................... L. mon sp. nov. – Abdomen dorsally with lively pattern, tergum V much brighter than neighbouring terga (Figs 1d, 4a) ............................................................4 4(3) Abdomen dorsally dark grey with yellowish pattern as in Fig. 4a, especially yellowish oval markings on terga III and V ...........L. lahu sp. nov. – Abdomen dorsally grey-brown, laterally whitish with black markings, terga V and X brighter (Fig. 1d) ................................................ L. multus 5(2) Left mandible with angular hump at margin between prostheca and mola (Fig. 11h) ........................................................ L. angularis sp. nov. – Left mandible without angular hump at margin between prostheca and mola ..................................................................................................6 6(5) Abdomen dorsally grey-brown, tergum II laterally darker with dark brown, roundish, distomedial marking, tergum V dark brown ... L. tonsator sp. nov. – Abdomen dorsally rather uniform brown ..............................................7 7(6) Labial palp segment III approx. as long as wide at base (Müller-Liebenau 1984: fig. 11g); claw with 10–12 denticles; paraproct with patch of notched scales (similar to Kaltenbach and Gattolliat 2019a: fig. 3g, h) .......................................................................... L. numeratus – Labial palp segment III rather short (length 0.8× width at base; Fig. 8d); claw with ~14 denticles; paraproct without patch of notched scales ... ..................................................................... L. tenasserimensis sp. nov.
268 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand 8(1) Labrum dorsally with arc of feathered setae (operosus species group) ......................................................................................................9 – Labrum dorsally with arc of clavate setae (sumigarensis species group) ....................................................................................................12 9(8) Labial palp segment II with broad thumb-like (lobed), distolateral protuberance, segment III oblong; maxillary palp segment II with slightly developed distolateral excavation (Kaltenbach and Gattolliat 2019b: fig. 36g, h) ..................................................................L. cf. paraoperosus – Labial palp segment II with rather narrow or elongate thumb-like, distomedial protuberance (Figs 16a, 17c; Kaltenbach et al. 2022a: fig. 1i), segment III slightly pentagonal; maxillary palp segment II with well-developed, distolateral excavation (Fig. 17g) ..............................10 10(9) Labial palp segment II with thumb-like, distomedial protuberance, slightly bent distad; paraproct at inner, proximal margin with additional submarginal row of minute spines (Kaltenbach et al. 2022a: figs 1i, 2 f, g) .................................................................................................... L. brao – Labial palp segment II with thumb-like, distomedial protuberance, directed laterally, proximal margin of protuberance slightly concave (Figs 16e, 17c); paraproct without additional submarginal row of minute spines ..............................................................................................11 11(10) Distomedial protuberance of labial palp segment II shorter than base of segment III (~0.8×) (Fig. 16e) .......................................... L. operosus – Distomedial protuberance of labial palp segment II elongated, longer than base of segment III (~1.2×) (Fig. 17c) .......... L. nisaratae sp. nov. 12(8) Tergalii on abdominal segments I–VII...................... L. septem sp. nov. – Tergalii on abdominal segments II–VII ...............................................13 13(12) Antennal scape with reduced, distolateral process (Müller-Liebenau 1984: fig. 6f) ..........................................................................L. diffundus – Antennal scape without distolateral process ...................................... 14 14(13) Thorax dorsally ochre with pronounced, dark brown, distolateral markings on mesonotum; abdomen dorsally dark reddish-brown, slightly paler in middle area, tergum I ochre; abdomen ventrally mainly beige, laterally dark reddish-brown (Fig. 20a, b) .................... L. karen sp. nov. – Thorax dorsally pale brown, no pronounced distolateral markings on mesonotum; abdomen dorsally pale brown, ventrally rather uniform beige ......................................................................................................15 15(14) Posterior margin of abdominal terga with triangular spines, sometimes spaced; abdominal terga dorsally rather uniform brown (Kaltenbach et al. 2022a: figs 4d, 5c) .........................................................L. kui – Posterior margin of abdominal terga with triangular, sharply pointed spines (Fig. 31g); abdominal terga dorsally brown with crown-like pattern (paler in anterior parts of seg; Fig. 28c) ..... L.ranongensis sp. nov. Discussion Assignment to Labiobaetis For the assignment of the new species to Labiobaetis we refer to Kluge and Novikova (2014), Müller-Liebenau (1984), and McCafferty and Waltz (1995).
269 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand Figure 31. Habitats: a. Labiobaetis multus; b. Labiobaetis mon sp. nov. (TL) and angularis sp. nov. (TL); c. Labiobaetis lahu sp. nov.; d. Labiobaetis tenasserimensis sp. nov. (TL); e. Labiobaetis tonsator sp. nov. (TL); f. Labiobaetis nisaratae sp. nov. and L. karen sp. nov. (TL); g. Labiobaetis septem sp. nov.; h. Labiobaetis ranongensis sp. nov. (TL). TL: type locality.
276 ZooKeys 1258: 213–276 (2025), DOI: 10.3897/zookeys.1258.166681 Thomas Kaltenbach et al.: New species of Labiobaetis from Thailand Shi W, Tong X (2014) The genus Labiobaetis (Ephemeroptera: Baetidae) in China, with description of a new species. Zootaxa 3815(3): 397–408. https://doi.org/10.11646/ zootaxa.3815.3.5 Shorthouse DP (2010) SimpleMappr, an online tool to produce publication-quality point maps. [Retrieved from https://www.simplemappr.net, Accessed March 03, 2021] Sivaruban T, Srinivasan P, Barathy S, Isack R (2022) A new species and record of Labiobaetis Novikova & Kluge, 1987 (Ephemeroptera: Baetidae) from India. Aquatic Insects 43(4): 319–334. https://doi.org/10.1080/01650424.2022.2070217 Sutthinun C, Gattolliat J-L, Boonsoong B (2018) A new species of Platybaetis Müller-Liebenau, 1980 (Ephemeroptera: Baetidae) from Thailand, with description of the imago of Platybaetis bishopi Müller-Liebenau, 1980. Zootaxa 4378(1): 85–97. https://doi. org/10.11646/zootaxa.4378.1.5 Suttinun C (2021) Systematics of family Baetidae (order Ephemeroptera) in southern and western Thailand. Doctoral thesis, Kasetsart University, Bangkok, 170 pp. Suttinun C, Gattolliat J-L, Boonsong B (2020) Cymbalcloeon gen. nov., an incredible new mayfly genus (Ephemeroptera: Baetidae) from Thailand. PLoS One 15(10): 1–17. https://doi.org/10.1371/journal.pone.0240635 Suttinun C, Kaltenbach T, Gattolliat J-L, Boonsoong B (2021) A new species and first record of the genus Procerobaetis Kaltenbach & Gattolliat, 2020 (Ephemeroptera, Baetidae) from Thailand. ZooKeys 1023: 13–28. https://doi.org/10.3897/zookeys.1023.61081 Suttinun C, Gattolliat J-L, Boonsoong B (2022) First report of the genus Tenuibaetis (Ephemeroptera, Baetidae) from Thailand revealing a complex of cryptic species. ZooKeys 1084: 165–182. https://doi.org/10.3897/zookeys.1084.78405 Tamura K, Stecher G, Kumar S (2021) MEGA 11: Molecular evolutionary genetics analysis version 11. Molecular Biology and Evolution 38(7): 3022–3027. https://doi. org/10.1093/molbev/msab120 Tofilski A (2018) DKey software for editing and browsing dichotomous keys. ZooKeys 735: 131–140. https://doi.org/10.3897/zookeys.735.21412 Tungpairojwong N, Phlai-ngam S, Jacobus LM (2022) A new species of Acentrella Bengtsson, 1912 (Ephemeroptera: Baetidae) from Thailand. Zootaxa 5125(4): 351– 378. https://doi.org/10.11646/zootaxa.5125.4.1 Vuataz L, Sartori M, Wagner A, Monaghan MT (2011) Toward a DNA taxonomy of Alpine Rhithrogena (Ephemeroptera: Heptagenidae) using a mixed Yule-Coalescent Analysis of mitochondrial and nuclear DNA. PLoS One 6(5): 1–11. https://doi.org/10.1371/ journal.pone.0019728 Supplementary material 1 Labiobaetis species of Thailand, genetic distances (COI, K2P) Authors: Thomas Kaltenbach, Jean-Luc Gattolliat, Boonsatien Boonsoong, Chanaporn Suttinun Data type: xls Copyright notice: This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Link: https://doi.org/10.3897/zookeys.1258.166681.suppl1