Taxonomic notes on the genus Baetiella Uéno, 1931 (Ephemeroptera, Baetidae), with description of three new species from Thailand.

Based on material recently collected in northern Thailand, the present study provides an updated of the genus Baetiella, including Gratia. It comprises six species in Thailand, three of them being new species: Baetiella (Gratia) narumonae, Baetiella (Gratia) sororculaenadinae, Baetiella (Baetiella) bispinosa, Baetiella (Baetiella) baeisp. nov., Baetiella (Baetiella) lannaensissp. nov. and Baetiella (Baetiella) bibranchiasp. nov.Baetiella (Baetiella) baeisp. nov. can be distinguished from other species by the reduction of the posteromedian protuberances on abdominal tergites I-III, the asymmetrical coniform terminal segment of labial palp, the distal margin of abdominal sternites VII-X each with a row of long, spatulate setae, the dorsal margin of femur with two long, robust setae distally. Baetiella (Baetiella) lannaensissp. nov. is diagnosed by the posteromedian protuberances present on tergites I-VIII, dorsal margin of femur with a regular row of long, rounded, ciliated setae and body surface covered with numerous, dense, rounded scale-like setae. Baetiella (Baetiella) bibranchiasp. nov. can be separated from other species by coxal gills present at the base of forelegs and midlegs. The molecular study based on the mitochondrial gene COI and a larval key to species of Thai Baetiella are also provided.

Taxonomic review of the Oriental genus Polyplocia Lestage, 1921 (Ephemeroptera, Euthyplociidae), with two new records for Thailand.

Previously, the euthyplociid mayfly from Thailand was reported as Polyplocia spp. without designation to any nominal species. In this study, the genus Polyplocia Lestage, 1921 in Thailand was reviewed. Two species are recognized: Polyplociaorientalis Nguyen & Bae, 2003 and P.nebulosa Gonçalves & Peters, 2016. This is the first report of P.nebulosa in Continental Asia. Cytochrome c oxidase subunit I (COI) data and illustrations based on nymphal characters were used to confirm two different species in Thailand. Additional morphological characteristics of the nymph and eggs of the two species from Thailand are also shown in detail. The taxonomic status of Polyplocia in the Oriental region is reviewed. Keys to known nymphal and imaginal stages are provided and the distribution of Polyplocia in the Oriental region is discussed.

Unravelling the diversity of the genus Afronurus Lestage, 1924 (Ephemeroptera, Heptageniidae) in Thailand.

The genus Afronurus in Thailand is investigated using an integrative approach (morphology based, ootaxonomy and molecular data) for species delimitation. A total of four species of Afronurus was identified; A.cervina (Braasch & Soldán, 1984), A.gilliesiana (Braasch, 1990), A.rainulfiana (Braasch, 1990), and A.rubromaculata (You et al., 1981). The subimago of A.gilliesiana is described for the first time based on reared specimens. The egg structure of all four species is also described for the first time. Morphological and molecular data strongly support their species delimitation. The egg chorionic structure of the genus Afronurus, together with other morphological characters, is useful for species identification. A key to mature nymphs of the known species is provided.

First report of the genus Tenuibaetis (Ephemeroptera, Baetidae) from Thailand revealing a complex of cryptic species.

A new species of the genus Tenuibaetis Kang & Yang, 1994 is described from Thailand and the genus is reported for the first time from this country. Tenuibaetispanhai sp. nov. is easily distinguished from other known Tenuibaetis by the complete absence of hindwing pads. Molecular evidence based on COI confirmed the validity of the new species. Additional putative species of Tenuibaetis based on molecular evidence only are considered as Molecular Operational Taxonomic Units (MOTUs) without description. The morphological characters of the new species and its closely related species are discussed; a key to the Oriental species is provided.

Cincticostellaebura sp. nov., a new species of mayfly (Ephemeroptera, Ephemerellidae) from Thailand.

A new species of ephemerellid mayfly, Cincticostellaebura sp. nov., is described based on larvae collected in a stream from Nan Province, Thailand. This new species is classified in the nigra complex of the genus Cincticostella based on morphological and COI phylogeny evidence. The new species is closely related to C.nigra (Uéno, 1928) and C.funki Martynov, Selvakumar, Palatov & Vasanth, 2021 based on body colour pattern. Investigation of the chorionic structure of the new species showed similar details to those of other species within this species complex. The phylogeny also placed this species into a monophyletic group with C.nigra (Uéno, 1928), C.elongatula (McLachlan, 1875) and C.fusca Kang & Yang, 1995.

Megabranchiella gen. nov., a new mayfly genus (Ephemeroptera, Baetidae) from Thailand with description of two new species.

Megabranchiella gen. nov. (Ephemeroptera: Baetidae) is established as a new baetid mayfly genus from northern Thailand. Two new species, Megabranchiellascutulata sp. nov. and Megabranchiellalongusa sp. nov., are described. This genus is distinguished from other Baetidae by abdominal segment I, bearing a pair of enlarged, ventrally oriented single gills, covering abdominal sternites II-V; other gills have normal size and are dorsolaterally oriented. The two new species Megabranchiellalongusa sp. nov. and Megabranchiellascutulata sp. nov. can be differentiated by the setation of femur dorsal margin and the shape of abdominal gill I. This mayfly genus was found in flowing water with cobble microhabitats in headwater streams of northern Thailand.

Behningiidae and Potamanthidae (Insecta, Ephemeroptera) in Thailand.

The aim of this study is to review the family Behningiidae and Potamanthidae in Thailand. Two genera and three species of Behningiidae are recognised: Protobehningiamerga Peters & Gillies, 1991, Behningiabaei McCafferty & Jacobus, 2006, and Behningianujiangensis Zhou & Bisset, 2019, which is newly reported from Thailand. The egg structure of B.nujiangensis is described for the first time using scanning electron microscopy. The larva of P.merga is redescribed and its distribution is expended northward with a new record from Chiang Mai province. Two genera and five species of Potamanthidae are identified: Potamanthusformosus Eaton, 1892, Rhoenanthusmagnificus Ulmer, 1920 (new record for Thailand), Rhoenanthusobscurus Navás, 1922, Rhoenanthusdistafurcus Bae & McCafferty, 1991, and Rhoenanthusspeciosus Eaton, 1881. Our morphological evidence is supported by COI data for the family Potamanthidae. Diagnostic characters, distributions, and keys are presented for the larvae of all known species of Thai behningiid and potamanthid mayflies.

First record of Paegniodes Eaton, 1881 (Ephemeroptera, Heptageniidae) from Thailand with description of a new species.

A new species of Heptageniidae, Paegniodes sapanensis sp. nov., is described based on larvae, subimagos, eggs, and COI data. The mayfly genus Paegniodes Eaton, 1881 is reported for the first time from Thailand. The larva of the new species can be distinguished from other known Paegniodes species by i) lamellae of gill I ca 1/4 of fibrilliform portion and ii) mandibles and basal segment of maxillary palp without dense setae on margin. The subimago characters useful to distinguish this new species from previously known species are i) the median stripes on abdominal terga and ii) shape of the female subgenital and subanal plates. The genetic distance between the new species and P. cupulatus (Eaton, 1871) was approximately 11%. The morphological characters of the new species are discussed and compared to other known species.

A new species and first record of the genus Procerobaetis Kaltenbach & Gattolliat, 2020 (Ephemeroptera, Baetidae) from Thailand.

The genus Procerobaetis Kaltenbach & Gattolliat, 2020 is reported for the first time from Thailand, and Procerobaetis totuspinosus sp. nov. is described as a new species based on larvae. It can be easily distinguished from other known Procerobaetis species by the presence of triangular spines at the posterior margin of tergites VI-IX. COI sequences were obtained from all known species. The genetic distances (Kimura 2-parameter) between the new species and the other species are between 20% and 23%. The morphological characters of the new species and its closely related species are discussed; larval key to all species of the genus Procerobaetis is also provided.

Stylogomphus thongphaphumensis (Odonata: Anisoptera: Gomphidae), a new gomphid dragonfly and the first record of S. malayanus Sasamoto, 2001 from Thailand.

Stylogomphus thongphaphumensis sp. nov. is described from a type series of specimens reared from larvae (holotype ♂, Huai Khayeng, Thong Pha Phum district, Kanchanaburi Province; 14°36'20″N 98°34'38″E, 206 m a.s.l., larva collected on 14.XII.2014; adult emerged on 30.IV.2015). All larvae were collected from the same locality in western Thailand. Description of the larva (based on preserved exuviae) is provided as well. The adult of this species can be distinguished from other Stylogomphus Fraser, 1922, by the morphology of the male anal appendages, pterothoracic pattern, abdominal pattern, male genitalia and female valvula vulvae (detail provided in the differential diagnosis below). This is the first species of Stylogomphus to be described from Thailand. This study also reports the first record of Stylogomphus malayanus Sasamoto, 2001, from Thailand.

Cymbalcloeon gen. nov., an incredible new mayfly genus (Ephemeroptera: Baetidae) from Thailand.

The genus Cymbalcloeon gen. nov. (Ephemeroptera: Baetidae) is established for a new species Cymbalcloeon sartorii sp. nov. from Thailand, based on larval stage. This genus is unique among all of the Baetidae by the presence of three pairs of single gills on segments V-VII, ventrally oriented to cover the sterna VI-IX. Cymbalcloeon sartorii gen. nov. et sp. nov. presents unique or rare morphological characters such as a deeply concave margin between the prostheca and mola, without setae; a very large subtriangular process of the left mandible; a maxillary palp segment II with scarce and very long setae; almost completely fused labial palp segments II and III with numerous very long setae; elongate tarsal claw with two rows of teeth; a shagreen surface of the terga and paraproct; and a very reduced body size. The gills of the new genus move very quickly during respiration and present a near-synchronous protraction. Due to the very derived larval morphological character and the unknown imaginal stage, the exact phylogenetic position of the genus remains unclear; it most certainly belongs to the concept of Anteropatellata and is possibly closely related to the genus Baetopus.

A New Species of Vietnamella Tshernova 1972 (Ephemeroptera: Vietnamellidae) from Thailand.

The larva, male subimago, female imago, and eggs of V. nanensis sp. n. are described based on specimens from Mae Hong Son and Nan provinces, Thailand. The female subimago is described based on a photograph of a specimen reared to the imago stage. The species previously was distinguished only by DNA barcode data and designated as Vietnamella sp. C. Based on morphology, the larva of the new species can be distinguished with the following combination of characteristics: (i) pattern of serration on the ventral margin of the forefemur, (ii) posterolateral margins of abdominal terga with pairs of acute tubercles, especially terga VI and VII, (iii) a well-developed pair of median ridge projections on tergum X, (iv) the second segment of the maxillary palp being about 1.3× the length of the third segment, and (v) females containing eggs with prominent protuberances on the chorionic surface. A key to larvae of all known species in the genus is provided.

Review of Notacanthella Jacobus amp; McCafferty, 2008 (Ephemeroptera: Ephemerellidae) in Thailand, with the redescription of Notacanthella commodema (Allen, 1971).

Larvae of the Notacanthella Jacobus McCafferty, 2008 species N. commodema (Allen, 1971) and N. quadrata (Kluge Zhou, 2004) from Thailand are compared and redescribed. Both species have serrations on maxillary canines, as does N. perculta (Allen, 1971) from Vietnam, and this contributes to synonymizing the subgenus Samiocca Jacobus McCafferty, 2008 under Notacanthella s.s. (= Samiocca n. syn.). The Thailand species can be differentiated by the numbers of thoracic and abdominal tubercles. In addition, the chorionic structure of N. quadrata is investigated for the first time by scanning electron microscopic technique.

Vietnamellidae (Insecta, Ephemeroptera) of Thailand.

The genus Vietnamella Tshernova, 1972 is investigated in detail for the first time in Thailand. As a consequence, four species are recognized, namely Vietnamella maculosa sp. nov., Vietnamella thani Tshernova, 1972, Vietnamella sp. B and Vietnamella sp. C. Herein, larvae and eggs of V. maculosa sp. nov. are described and reported from Chiang Rai Province. The larva of Vietnamella sp. B from Tak Province is also described, but not named due to insufficient material, and the imaginal stages and eggs of V. thani Tshernova, 1972 are described and presented for the first time. Our morphological evidence is supported with COI data. The phylogeny showed that four different lineages of the genus Vietnamella occur in Thailand, one of them, viz., Vietnamella sp. C, only known from a couple of COI sequences retrieved from the Barcode of Life Data System (BOLD). Diagnoses for all known Oriental species are also presented.

Review and integrative taxonomy of the genus Prosopistoma Latreille, 1833 (Ephemeroptera, Prosopistomatidae) in Thailand, with description of a new species.

Three species of the genus Prosopistoma Latreille, 1833 (Prosopistomatidae) are currently reported from Thailand. A new species, Prosopistomacarinatum sp. n., is described here based on specimens from western and southern Thailand. The new species can be easily distinguished from the other members of Prosopistoma by the following combination of characteristics: (i) the presence of two ridged longitudinal lines on each side of its carapace, (ii) antenna 7-segmented, (iii) a strongly convex carapace and (iv) nine pectinate setae on the ventral margin of the fore tibiae. A comparison between the key characteristics of P.carinatum sp. n. and the known Thai species is provided. Results of analysis of the mitochondrial cytochrome oxidase I (COI) gene (658 bp) of three species, as well as the distribution of the Thai species, are also discussed.

A review of genus Agriocnemis larva (Odonata: Coenagrionidae) from Thailand including a description of the final stadium larva of Agriocnemis minima Selys, 1877 with supporting molecular (COI) data.

The larva of Agriocnemis minima Selys, 1879 is described and illustrated for the first time, based on reared specimens collected from Thailand. Selected larvae of Agrioncnemis Selys, 1877 were matched with their adults by DNA barcoding. The mitochondrial COI gene (658 bp) of three species (A. minima, A. femina femina (Brauer, 1868), and A. pygmaea (Rambur, 1842)) occurring in Thailand was analysed to confirm the species identification and to determine the association between the larva and adult stages. The larva of A. minima can be distinguished from known species by the following combination of characteristics: 1) long simple setae on the antennomeres I and II, 2) protrusion of the male cerci as long as 0.5× the S10, and 3) tufts of spiniform setae on the lateral occiput margin and on the ventral view of the compound eyes. Comparisons to known larvae of Agriocnemis and those of some other subfamily Agriocnemidinae members are also provided.

A new species of Platybaetis Müller-Liebenau, 1980 (Ephemeroptera: Baetidae) from Thailand, with description of the imago of Platybaetis bishopi Müller-Liebenau, 1980.

Platybaetis bishopi Müller-Liebenau, 1980 was originally described from Malaysia only at the larval stage. We provide the first description of the imaginal stage of P. bishopi based on materials from Thailand. The imago of this species can be separated from the known species by coloration of abdominal terga and coloration of wings. A new species, Platybaetis nayokensis sp. nov., is described based on male and female imagos and larvae from Thailand. The larva of this species is mainly distinguished by medium acute spines on the posterior margin of the abdominal terga and two apical setae on the glossa, which seem to be shorter than in other species. The imago can be separated by the abdominal color pattern. The larva of this genus is adapted to live on wet rocks projecting out of water; it prefers large stones near small waterfalls or areas between two large rocks in running water.

Description of the final instar larva of Pseudagrion pruinosum (Burmeister, 1839) (Odonata: Coenagrionidae) from Thailand.

Herein the final instar larva of Pseudagrion pruinosum (Burmeister, 1839) is described and illustrated for the first time, based on reared specimens from Thailand. When compared with the other known Pseudagrion larvae, P. pruinosum is distinguished by three setae on the labial palp, five teeth on the truncate, denticulate lobe on the distal marginal end of the labial palp, one premental seta and a row of three minute setae on each side of the midline, as well as shape and tracheation of caudal gills.

Sangpradubina, an astonishing new mayfly genus from Thailand (Ephemeroptera: Leptophlebiidae: Atalophlebiinae).

A newly discovered representative of Leptophlebiidae is described and illustrated from Thailand as Sangpradubina thailandica, gen. nov. and sp. nov., based on larvae and reared adults. This new species presents an interesting transitional position, being close to Choroterpes s.l. in the winged stages, but closer to Thraulus s.l. in the nymphal stage.   Nymphs are differentiated from those of all genera of the Thraulus lineage by the combination of gill I consisting of only a single and slender lamella, gills II-VII being fimbriate only in the distal half, each mandible having a tuft of setae only in the middle of the lateral margin, each maxilla having a well-developed anterolateral projection, fore- and middle femora each having a row of long setae on the outer margin, as well as tarsal claws having 4 denticles at the base and 9 in the apical position. Adults of the new genus barely differ from any genera of the Choroterpes lineage. The egg chorionic structure of Sangpradubina also appears to be unusual in that KCT's are concentrated on one pole.

Description of two final stadium Onychogomphus larvae from Thailand (Odonata: Gomphidae).

The final stadium larvae of Onychogomphus castor Lieftinck and O. duaricus Fraser are described and illustrated for the first time based on reared specimens from Thailand. The taxonomic characteristics of the larvae of the genus Onychogomphus are discussed and summarized. The larva of O. castor differs from other Southeast Asian species in having distinct mid-dorsal spines on S2-9, divergent wing pads reaching S5, and lateral spines on S6-9. The larva of O. duaricus has a weakly swollen third antennal segment, with short blunt mid-dorsal spines on S2-9, divergent wing sheaths reaching the middle of S4, and lateral spines present on S7-9.