A monograph on the genus Tetraserica from the Indochinese region (Coleoptera, Scarabaeidae, Sericini)

Abstract In this monograph on the Indochinese species of Tetraserica Ahrens, 2004 all species distributed in Thailand, Laos, Vietnam, Cambodia, Myanmar, and mainland Malaysia are covered as well as those of the Indian province Mizoram. From this revision, the following new combinations result: Tetrasericagressitti (Frey, 1972), comb. n., T.laotica (Frey, 1972), comb. n., T.satura (Brenske, 1898), comb. n., T.sejugata (Brenske, 1898), comb. n., T.siantarensis (Moser, 1922), comb. n., T.spinicrus (Frey, 1972), comb. n., T.vietnamensis (Frey, 1969), comb. n., and T.wapiensis (Frey, 1972), comb. n. Two new synonyms were found: Tetrasericamidoriae Kobayashi, 2017 (syn. n.) = T.laotica (Frey, 1972); T.graciliforceps Liu et al. 2014 (syn. n.) = T.satura (Brenske, 1898). The lectotypes of Tetrasericagestroi (Brenske, 1898), T.miniatula (Moser, 1915), and T.siantarensis (Moser, 1922) are designated. 116 Tetraserica species were recorded from Indochina, among which 88 new species are described: Tetrasericaallochangshouensissp. n., T.allomengeanasp. n., T.allosejugatasp. n., T.angkorthomensissp. n., T.angkorwatensissp. n., T.appendiculatasp. n., T.auriculatasp. n., T.bachmaensissp. n., T.banhuaipoensissp. n., T.bansanpakianasp. n., T.bolavensensissp. n., T.breviforcepssp. n., T.cattienensissp. n., T.champassakanasp. n., T.constantisp. n., T.cucphongensissp. n., T.curviforcepssp. n., T.desalvazzaisp. n., T.doiphukhaensissp. n., T.doipuiensissp. n., T.doisuthepensissp. n., T.dongnaiensissp. n., T.falciforcepssp. n., T.falciformissp. n., T.feresiantarensissp. n., T.filiforcepssp. n., T.fullerisp. n., T.phukradungensissp. n., T.geiseraesp. n., T.giulianaesp. n., T.infidasp. n., T.jaklisp. n., T.khaosoidaoensissp. n., T.kiriromensissp. n., T.koisp. n., T.kollaesp. n., T.konchurangensissp. n., T.kontumensissp. n., T.loeiensissp. n., T.lucaisp. n., T.microfurcatasp. n., T.microspinosasp. n., T.multiangulatasp. n., T.nahaeoensissp. n., T.nakaiensissp. n., T.namnaoensissp. n., T.neouncinatasp. n., T.nonglomensissp. n., T.nussisp. n., T.olegisp. n., T.pahinngamensissp. n., T.pailinensissp. n., T.parasetuliforcepssp. n., T.paratonkinensissp. n., T.petrpacholatkoisp. n., T.phatoensissp. n., T.phoupaneensissp. n., T.pluriuncinatasp. n., T.pseudoliangheensissp. n., T.pseudoruiliensissp. n., T.pseudouncinatasp. n., T.quadriforcepssp. n., T.quadrifurcatasp. n., T.rihaisp. n., T.romaesp. n., T.rubrithoraxsp. n., T.sapanasp. n., T.semidamadiensissp. n., T.semipingjiangensissp. n., T.semiruiliensissp. n., T.semishanensissp. n., T.setuliforcepssp. n., T.shanensissp. n., T.smetsisp. n., T.margheritaesp. n., T.sopponganasp. n., T.spanglerorumsp. n., T.spinotibialissp. n., T.subrotundatasp. n., T.tanahrataensissp. n., T.thainguyensissp. n., T.trilobiforcepssp. n., T.ululalatensissp. n., T.umphangensissp. n., T.varisp. n., T.veliformissp. n., T.vientianeensissp. n., and T.xiengkhouangensissp. n. A key to the Indochinese Tetraserica species is given and distributions as well as the habitus and male genitalia of all species are illustrated.


Introduction
While the genus Tetraserica Ahrens, 2004 included earlier only species from Indian subcontinent and Myanmar, Liu et al. (2014) added a significant number of species from China and recently additional species were described by Ahrens and Fabrizi (2016) from northeastern India and by Kobayashi (2017Kobayashi ( , 2018 from Thailand. Several molecular phylogenetic analyses confirmed the monophyly of Tetraserica (Ahrens & Vogler, 2008;Liu et al. 2015;Eberle et al. 2016). Based on a thorough examination of all type material of Asian mainland Sericini and an assessment of DNA-informed species boundaries (Dalstein et al. 2019) we revise here the taxonomy of the Tetraserica species so far known from Indochina. We found 88 new species, which are described herein. A key to the Indochinese Tetraserica species is given, and their distributions, as well as habitus and male genitalia, are illustrated.

Materials and methods
The terminology and methods used for measurements, specimen dissection, and genital preparation follow Ahrens (2004). Data from specimens examined are cited in the text with original label contents given in quotation marks, multiple labels are separated by a "/". Male genitalia were glued to a small pointed card attached to the specimen. Descriptions and illustrations of new taxa are based on the holotype or lectotype specimen, while the variation of other specimens is given separately. All descriptions and measurements were made under an Olympus SZX 12 microscope, and all genital and habitus illustrations were made with a digital camera (AxioCam HRc) attached to a stereo microscope (Zeiss Stereo Discovery V20) and Axio Version 4.8 software. The distribution maps were generated using Q-GIS 2.0.1 and Inscape software. Type specimens and other examined material are deposited in the following institutions or collections:  Liu et al. 2014: 83;Ahrens and Fabrizi 2016: 122;Kobayashi 2017Kobayashi : 33, 2018 Diagnosis. Body moderately large to large (6-12 mm), mostly dark brown; ventral surface reddish brown; dorsal surface dull and glabrous. Labroclypeus subtrapezoidal, wider than long, widest at base, lateral margins moderately convex and convergent to strongly rounded anterior angles, anterior margin weakly sinuate medially, margins moderately reflexed; surface weakly convex, moderately shiny, finely and densely punctate; frontoclypeal suture indistinctly incised, flat and weakly curved medially; ocular canthus short and triangular, impunctate, with a single terminal seta. Frons dull, with sparse, fine punctures, with single erect setae beside each eye. Antenna yellowish, with ten antennomeres; club composed of four antennomeres in male, straight, rarely longer than 1.5 times as the remaining antennomeres combined; club in female composed of three antennomeres, as long as the remaining antennomeres combined. Mentum elevated and slightly flattened anteriorly.

BPBM
Pronotum moderately wide and strongly convex, lateral margins evenly convex, more strongly narrowed anteriorly towards sharp and slightly produced anterior angles. Anterior margin of pronotum slightly convex, with fine complete marginal line. Posterior angles blunt or strongly rounded. Surface finely and densely punctate, except minute setae glabrous, lateral and lateral anterior margins sparsely setose. Hypomeron not carinate. Scutellum triangular, finely and densely punctate.
Elytra oblong, widest just behind middle, striae distinctly impressed, finely and moderately densely punctate, intervals distinctly convex, with coarse and dense punctures concentrated along striae, with very minute setae in punctures; epipleural edge robust, ending at weakly curved and slightly blunt external apical angle of elytra, epipleura densely setose, apical border with a broad fringe of microtrichomes (100×).
Ventral surface weakly shiny, finely and densely punctate, metasternum sparsely covered with fine, short, or very minute setae, metacoxa glabrous, with a few single setae laterally; abdominal sternites finely and densely punctuate, with a transverse row of coarse punctures, each bearing a robust seta. Mesosternum between mesocoxae as wide as mesofemur. Pygidium weakly convex and dull, densely punctate, without smooth midline, almost glabrous, but with a few longer setae along apical margin; pygidium without strong sexual dimorphism.
Legs moderately wide; femora finely and sparsely punctate; metafemur wide and moderately shiny or dull, anterior margin acute, posterior margin smooth ventrally and only weakly widened in apical half, posterior margin smooth dorsally, with a few short setae basally. Posterior margin of metafemur generally straight or slightly convex. Metatibia moderately wide to wide and moderately long, widest at half of metatibial length, dorsal margin sharply carinate, with two groups of spines; lateral face finely and sparsely punctate; ventral edge finely serrated, with four robust equidistant setae, medial face smooth, apex interiorly near tarsal articulation with a shallow sinuation. Tarsomeres with fine, very dense setae ventrally on distal half, neither laterally nor dorsally carinate, dorsally smooth; metatarsomeres with a strongly serrated ridge ventrally and glabrous; first metatarsomere slightly shorter than two following tarsomeres combined, one third of its length longer than dorsal tibial spine. Protibia short, bidentate; anterior claws symmetrical, basal tooth of both claws bluntly truncate at apex.
Aedeagus: Phallobase with a more or less long median ventral extension (median phallobasal lamina).
Remarks. Tetraserica differs from closely related genera, Microserica Brenske, 1894 and Trioserica Moser, 1922, by lacking the ventral carina on hypomeron. From Microserica it also differs by lacking the sexual dimorphism of the pygidium, from Trioserica by the bidentate protibia. In contrast to the Microserica, species of Tetraserica are active at night and are attracted by light.
Distribution. The genus is distributed almost in the entire Oriental region except the southern Indian subcontinent; we know that additional species described by various authors are so far assigned to "Neoserica" from Philippines, Sumatra, and Borneo but that awaits a formal revision (Ahrens 2004  Description. Length of body: 8.9 mm; length of elytra: 6.8 mm; maximum width: 5.4 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.67. Ratio of length of metepisternum/metacoxa: 1/1.53. Metatibia moderately long and wide, ratio width/length: 1/3.77; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica finociliata sp. n. differs from all other Tetraserica species by the long and robust distal lobe of right paramere being strongly curved upwards (lateral view), and having a strong subapical ventral tooth.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Latin words fino-(fine) and ciliatus (ciliate), with reference to the fine comp of trichomes at the base of the right paramere. Diagnosis. Tetraserica romae sp. n. differs from all other Tetraserica species by the right hammer-shaped paramere, which has a sharply pointed double spine at apex, one directed dorsally, and a larger one ventrally. Variation. Length of body: 8.8-9.8 mm; length of elytra: 7.1-7.9 mm; maximum width: 5.8-6.1 mm.
Diagnosis. The new species differs from the similar T. daqingshanica by the dorsal lobe of the right paramere being wide and straight in the basal half and curved in the apical half; the apex of left paramere gently narrows towards apex in T. neouncinata.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Greek word neo-(new) and Latin word uncinatus, with reference to the uncinated shape of the right paramere. Description. Length of body: 9.3 mm; length of elytra: 6.9 mm; maximum width: 5.9 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.58. Ratio of length of metepisternum/metacoxa: 1/1.7. Posterior margin of metafemur with blunt tooth. Metatibia moderately long and wide, ratio width/length: 1/3.31; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 2A-D. Habitus: Fig. 2E. Female unknown. Diagnosis. Tetraserica pseudouncinata sp. n. differs from T. neouncinata by the left paramere being two thirds as wide as length of the antennal club (rather than one quarter as wide as in T. neouncinata).
Etymology. The species name (adjective in the nominative singular) is derived from the combined Greek word pseudo-(false) and Latin word uncinatus, with reference to the uncinated shape of the right paramere. Description. Length of body: 11.8 mm; length of elytra: 7.5 mm; maximum width: 7 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.53. Ratio of length of metepisternum/metacoxa: 1/1.58. Metatibia short and wide, ratio width/ length: 1/3.21; basal group of dorsal spines of metatibia at first third of metatibial length. Variation. Length of body: 11.8-12.5 mm; length of elytra: 7.5-9.2 mm; maximum width: 6.4-7.0 mm.
Diagnosis. Tetraserica falciformis sp. n. differs in male genital shape from the similar T. sculptilis by having the posterior margin of metafemur straight rather than being blunt or with a tooth; furthermore, the dorsal lobe of the right paramere is markedly curved and strongly widened at base.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Latin words falcis-(sickle) and formis (of shape), with reference to the sickle-shaped right paramere. Diagnosis. Tetraserica pseudoliangheensis sp. n. differs from T. falciformis by the dorsal lobe of right paramere having a sharp hook at its apex (dorsal view). The species is also rather similar to T. liangheensis Liu et al., 2014; however, in the new species the posterior margin of metafemur does not possess a tooth and the dorsal lobe of the right paramere is much wider at the base.

Tetraserica sculptilis
Etymology. The species name (adjective in the nominative singular) is derived from the combined Latin words pseudo-(nearly) and the species name liangheensis, with reference to the similarity to T. liangheensis Liu et al., 2014.  Description. Length of body: 10.4 mm; length of elytra: 7.6 mm; maximum width: 6.6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.56. Ratio of length of metepisternum/metacoxa: 1/1.63. Posterior margin of metafemur with sharp hook. Metatibia moderately long and wide, ratio width/length: 1/4.14; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica trilobiforceps sp. n. differs from all other Tetraserica species by the left paramere having a dorsal lobe distant from base.
Etymology. The species name (noun in apposition) is derived from the combined Latin words tri-(three times), lobatus (lobed), and forceps, with reference to the shape of the left paramere. Description. Length of body: 9.1 mm; length of elytra: 6.9 mm; maximum width: 5.6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.68. Ratio of length of metepisternum/metacoxa: 1/1.63. Metatibia moderately long and wide, ratio width/length: 1/3.36; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 4E-G. Habitus: Fig. 4H. Female unknown. Diagnosis. Tetraserica phukradungensis sp. n. differs from T. trilobiforceps sp. n. species by the shorter and stouter left paramere which has a short fine dorsal lobe behind the middle (rather than before the middle as in T. trilobiforceps).
Etymology. The new species is named after the type locality, Phu Kradung (adjective in the nominative singular).
Description. Length of body: 7.3 mm; length of elytra: 5.5 mm; maximum width: 4.9 mm. Dorsal surface blackish, ventral surface reddish brown. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.48. Ratio of length of metepisternum/ metacoxa: 1/1.67. Metatibia moderately long and wide, ratio width/length: 1/3.33; basal group of dorsal spines of metatibia at first third of metatibial length. Diagnosis. This species differs from all other Tetraserica species in having a simple left paramere, by the strongly asymmetric phallobase (dorsal view), the very short median lamina of phallobase, and by having the right paramere more or less straight (ventral view).
Etymology. The new species is named after the type locality, Cuc Phuong (adjective in the nominative singular).  Female unknown. Diagnosis. Tetraserica thainguyensis sp. n. differs from the similar T. geiserae by having the left paramere very short and split into two lobes.

Tetraserica geiserae
Etymology. The new species is named with reference to its occurrence close to Thainguyen (adjective in the nominative singular). Description. Length of body: 8.6 mm; length of elytra: 6.5 mm; maximum width: 5.3 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.68. Ratio of length of metepisternum/metacoxa: 1/1.73. Metatibia moderately long and wide, ratio width/length: 1/3.62; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica xiengkhouangensis sp. n. differs from the similar T. damaidiensis by having the right paramere distinctly not wider (dorsal view) than the left one, and the left paramere short, one third as long as phallobase.
Etymology. The new species is named with reference to its occurrence in the Xieng Khouang province (adjective in the nominative singular).  Variation. Length of body: 6.5-7.8 mm; length of elytra: 5.4-6.0 mm; maximum width: 4.4-4.8 mm.

Tetraserica doisangensis Kobayashi, 2017
Diagnosis. Tetraserica curviforceps sp. n. differs from T. sigulianshanica Liu et al., 2014 by the distinctly finer and longer parameres. From T. doisangensis Kobayashi, 2017 it differs by the narrow median phallobasal apophysis and the strongly curved dorsal lobe of the right paramere.
Etymology. The species name (noun in apposition) is derived from the combined Latin words curvus (curved) and forceps, with reference to the shape of the curved right paramere.
Redescription. Length of body: 8.0 mm; length of elytra: 5.8 mm; maximum width: 4.8 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes large, ratio of diameter/interocular width: 0.72. Ratio of length of metepisternum/metacoxa: 1/1.62. Metatibia moderately long and wide, ratio width/length: 1/3.07; basal group of dorsal spines of metatibia at first third of metatibial length.
Female: Antennal club with three antennomeres, as long as remaining antennomeres combined. Eyes smaller than in male, ratio of diameter/interocular width: 0.64. Pygidium flat.
Description. Length of body: 7.6 mm; length of elytra: 5.9 mm; maximum width: 5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.77. Ratio of length of metepisternum/metacoxa: 1/1.52. Metatibia moderately long and wide, ratio width/length: 1/3.38; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica pluriuncinata sp. n. differs from T. bachmaensis by the left paramere being split into two long branches (or lobes) and by having much longer median phallobasal apophysis.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Greek word pluris (higher) and Latin word uncinatus (hooked), with reference to the pluri-hooked shape of the right paramere. Diagnosis. Tetraserica sapana sp. n. is similar to T. pluriuncinata sp. n. in shape of male genitalia but differs from the latter by the shorter and simpler left paramere and the presence of trichome-like spines on the dorsal lobe of the right paramere.
Etymology. The new species is named after the type locality, Sa Pa (adjective in the nominative singular).
Description. Length of body: 7.5 mm; length of elytra: 5.9 mm; maximum width: 4.6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.59. Ratio of length of metepisternum/metacoxa: 1/1.68. Metatibia moderately long and wide, ratio width/length: 1/3.33; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica setuliforceps sp. n. resembles T. changjiangensis Liu et al., 2014 in the shape of aedeagus but it differs by the distinctly longer dorsal lobe of right paramere, which also bears trichome-like spines, and by the nearly straight left paramere.
Etymology. The species name (noun in apposition) is derived from the combined Latin words setulus (with small setae) and forceps, with reference to the setae present on the right paramere.

Etymology. The species name (noun in apposition) is derived from the combined
Greek prefix para-(near) and the species name setuliforceps, with reference to the similarity to the previous species. Variation. Length of body: 7.5-7.8 mm; length of elytra: 5.6-5.8 mm; maximum width: 4.8-4.9 mm.
Diagnosis. Tetraserica kollae sp. n. is very similar to T. brahmaputrae Ahrens, 2004 in the shape of the genitalia; it differs from it by having a wider dorsal lobe of the right paramere, which is inserted more laterally on the right side, as well as the more strongly curved distal lobe of the right paramere.
Etymology. The new species is named after Dr Kolla Sreedevi, collector of the new species (noun in the genitive singular).  Diagnosis. The shape of aedeagus of T. jakli sp. n. is somewhat similar to that of T. ferrugata (Blanchard, 1850) from the Himalayas; the left paramere of the new species is, however, distinctly longer and distinctly split into two short filiform branches at apex.
Etymology. The new species is named after its collector, St. Jakl (noun in genitive singular). Description. Length of body: 8.8 mm; length of elytra: 6.5 mm; maximum width: 5.3 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.65. Ratio of length of metepisternum/metacoxa: 1/1.52. Metatibia short and wide, ratio width/length: 1/3.21; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. The shape of aedeagus of T. appendiculata sp. n. is very similar to that of T. mengeana Liu et al., 2014; the new species differs in having one filiform subbranch of the left paramere reduced, being much shorter than the width of principal branch at apical third.
Etymology. The species name (adjective in the nominative singular) is derived from the Latin word appendiculus (small appendage), with reference to the small appendix of the paramere. Description. Length of body: 8.9 mm; length of elytra: 6.6 mm; maximum width: 5.0 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes large, ratio of diameter/interocular width: 0.7. Ratio of length of metepisternum/metacoxa: 1/1.65. Metatibia moderately long and wide, ratio width/length: 1/3.36; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. The shape of aedeagus of T. allomengeana sp. n. is very similar to that of T. mengeana Liu et al., 2014; the new species differs by the filiform branches of left paramere being approximately two thirds of the paramere length, and by having the median phallobasal lamina evenly narrowed towards apex, rather than being narrow for most of its distal part as in T. mengeana.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Greek word allo-(other) and the species name mengeana, with reference to the similarity to T. mengeana. Description. Length of body: 8.9 mm; length of elytra: 6.8 mm; maximum width: 5.6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.62. Ratio of length of metepisternum/metacoxa: 1/1.67. Metatibia moderately long and wide, ratio width/length: 1/3.33; basal group of dorsal spines of metatibia at first third of metatibial length.
Variation. Length of body: 8.9-9.8 mm; length of elytra: 6.8-7.0 mm; maximum width: 5.5-5.6 mm. Female: Eyes as large as in male; antennal club composed of four antennomeres, basal joint of club one quarter as long as club.
Diagnosis. Tetraserica quadrifurcata sp. n. differs from all other Tetraserica species by its long median phallobasal apophysis having the median phallobasal lamina bifurcate at apex.

Tetraserica siantarensis
Diagnosis. Tetraserica feresiantarensis sp. n. differs from the very similar T. siantarensis Moser, 1915 by the median lamina of phallobase having no dorsal preapical tooth and the dorsal lobe of left parameres and median lamina of phallobase being as long as phallobase, rather than being distinctly longer as in T. siantarensis.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Latin words fere-(nearly) and the species name siantarensis, with reference to the similarity to T. siantarensis (Moser). Description. Length of body: 6.9 mm; length of elytra: 5 mm; maximum width: 3.9 mm. Body blackish brown, pronotum reddish. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.43. Ratio of length of metepisternum/metacoxa: 1/1.42. Metatibia short and wide, ratio width/length: 1/3.08; basal group of dorsal spines of metatibia at first third of metatibial length.
Etymology. The species name (noun in apposition) is derived from the combined Latin words rubus (red) and thorax, with reference to the red pronotum of the species. Description. Length of body: 6.9 mm; length of elytra: 5.1 mm; maximum width: 4.5 mm. Dorsal surface blackish, ventral surface reddish brown. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.44. Ratio of length of metepisternum/ metacoxa: 1/1.44. Metatibia moderately long and wide, ratio width/length: 1/3.8; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica falciforceps sp. n. is rather similar to T. sigulianshanica Liu et al., 2014 in shape of the aedeagus; the new species differs by the straight left paramere not being widened at apex and by the longer and widely arched dorsal lobe of the right paramere.
Etymology. The species name (noun in apposition) is derived from the combined Latin words falcis (sickle) and forceps, with reference to setae present to the sickleshaped right paramere.
Description. Length of body: 6.8 mm; length of elytra: 5.6 mm; maximum width: 0.1 mm. Dorsal surface blackish, ventral surface reddish brown. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.42. Ratio of length of metepisternum/metacoxa: 1/1.56. Metatibia short and wide, ratio width/length: 1/3.14; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica smetsi sp. n. is very similar to T. shangsiensis Liu et al., 2014 in shape of the aedeagus. The new species differs from the latter by the median lamina of phallobase being approximately as long as left paramere and slightly bifurcate at apex, as well as the preapical tooth of the left paramere being dorsally positioned and duplicate. In T. shangsiensis the median lamina of phallobase is distinctly shorter than left paramere, simply pointed, and slightly rounded at apex.
Etymology. The new species is named after one of its collectors, K Smets (noun in genitive singular). Description. Length of body: 9.3 mm; length of elytra: 7.3 mm; maximum width: 5.5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.77. Ratio of length of metepisternum/metacoxa: 1/1.83. Metatibia moderately long and wide, ratio width/length: 1/3.67; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica namnaoensis sp. n. is very similar to T. shangsiensis Liu et al., 2014 and T. smetsi sp. n. in shape of the aedeagus. The new species differs from these two species by the median lamina of its phallobase being distinctly curved and evenly narrowed from the base to apex, rather than being straight and strongly narrowed after the basal third.
Diagnosis. Tetraserica konchurangensis sp. n. is very similar to T. shangsiensis Liu et al., 2014, T. namnaoensis sp. n., and T. smetsi sp. n. in shape of the aedeagus. Tetraserica konchurangensis sp. n. differs from all three by the left paramere lacking a tiny tooth before the apex.
Etymology. The new species is named with reference to its occurrence in the Kon Chu Rang Nature Reserve (adjective in the nominative singular). Description. Length of body: 7.5 mm; length of elytra: 5.9 mm; maximum width: 4.9 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.68. Ratio of length of metepisternum/metacoxa: 1/1.79. Metatibia short and wide, ratio width/length: 1/3.07; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica angkorwatensis sp. n. is rather similar to T. gestroi (Brenske, 1898) in shape of aedeagus; the new species differs by having the median lamina of the phallobase curved at its apex dorsally, while the base of the left paramere is not extended ventrally.
Etymology. The new species is named after the type locality, Angkor Wat (adjective in the nominative singular).  Description. Length of body: 7 mm; length of elytra: 5.4 mm; maximum width: 4.5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.48. Ratio of length of metepisternum/metacoxa: 1/1.39. Metatibia short and wide, ratio width/ length: 1/3.25; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica koi sp. n. differs from all other species with the left paramere composed of two lobes at its base, by the right paramere being half as long as phallobase, and the left paramere longer than phallobase.
Etymology. The new species is named in honour of Prof Dr Ko, Silvia's oncologist and director of the Johanniter Hospital in Bonn, for all his efforts and care (noun in genitive singular). Description. Length of body: 9.1 mm; length of elytra: 7.1 mm; maximum width: 5.5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.53. Ratio of length of metepisternum/metacoxa: 1/1.73. Metatibia short and wide, ratio width/ length: 1/3.25; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica fulleri sp. n. differs from all other Tetraserica species in having long parameres and a long median phallobasal lamina, and by the simple left paramere being wide for its entire length (at middle nearly as wide as apex of phallobase; lateral view).
Etymology. The new species is named after its collector, E Fuller (noun in genitive singular). Description. Length of body: 9.5 mm; length of elytra: 7.4 mm; maximum width: 6.3 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.63. Ratio of length of metepisternum/metacoxa: 1/1.47. Metatibia moderately long and wide, ratio width/length: 1/3.69; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica paratonkinensis sp. n. is very similar to T. xichouensis Liu et al., 2014 in shape of aedeagus, but differs by the left paramere being nearly uniformly curved and the median lamina of phallobase that is not narrowed in its apical half.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Greek word para-(close to) and the species name tonkinensis, with reference to the similarity with T. tonkinensis (Moser).

Tetraserica tonkinensis (Moser, 1908) Figures 16, 51
Neoserica tonkinensis Moser, 1908: 328. Diagnosis. Tetraserica quadriforceps sp. n. differs from all other Tetraserica species with a median lamina of the phallobase that is longer than the half-length of phallobase (but not exceeding the length of it), and by the right paramere having a comb of short spines at base. The shape of aedeagus resembles that of T. changshouensis Liu et al., 2014, but the medial phallobasal lamina is much shorter and the apex of the right paramere less strongly widened.
Etymology. The species name (noun in apposition) is derived from the combined Latin prefix quadri (four) and forceps, with reference to the four branches of the parameres.  Description. Length of body: 8.8 mm; length of elytra: 6.6 mm; maximum width: 5.6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.56. Ratio of length of metepisternum/metacoxa: 1/1.5. Metatibia short and wide, ratio width/length: 1/3.27; basal group of dorsal spines of metatibia at first third of metatibial length.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Greek prefix allo-(other) and the species name changshouensis, with reference to the similarity to T. changshouensis.   Description. Length of body: 10 mm; length of elytra: 7.5 mm; maximum width: 6.4 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.62. Ratio of length of metepisternum/metacoxa: 1/1.61. Metatibia short and wide, ratio width/ length: 1/2.36; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica dongnaiensis sp. n. differs from all other Tetraserica species that have long median phallobasal lamina with simple left and simple right parameres at base (without brush of spines), by the left paramere being split behind basal third into two filiform branches, and the right paramere being short and curved.
Etymology. The new species is named with reference to its occurrence in the Dong Nai province (adjective in the nominative singular).
Description. Length of body: 8.3 mm; length of elytra: 6.1 mm; maximum width: 5.3 mm. Dorsal surface blackish, ventral surface reddish brown. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.43. Ratio of length of metepisternum/metacoxa: 1/0.04. Metatibia short and wide, ratio width/length: 1/3.07; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 18E-G. Habitus: Fig. 18H. Female unknown. Diagnosis. Tetraserica phatoensis sp. n. differs from all other Tetraserica species with very short median lamina of the phallobase (one quarter of phallobase length) and a long and narrow, more or less straight, left paramere, and by the right paramere having divergent spines at the base and a separate lobe distally.
Etymology. The new species is named after the type locality, Pha To (adjective in the nominative singular). Description. Length of body: 9 mm; length of elytra: 5.8 mm; maximum width: 5.8 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.71. Ratio of length of metepisternum/metacoxa: 1/1.72. Metatibia short and wide, ratio width/length: 1/2.05; basal group of dorsal spines of metatibia at first third of metatibial length. Ventral terminal spine of metatibia distinctly longer than first metatarsomere.
Diagnosis. Aedeagus of Tetraserica spinotibialis sp. n. resembles that of T. ruiliensis Liu et al., 2014 in shape. The new species differs by the ventral terminal spine of metatibia being distinctly longer than first metatarsomere, as well as by the right paramere being more strongly bent in the middle in lateral view.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Latin words spina and tibialis, with reference to the strongly developed spine of the mesotibia. length of metepisternum/metacoxa: 1/1.69. Metatibia short and wide, ratio width/length: 1/2.62; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica vari sp. n. differs from all other Tetraserica species in having a long median phallobasal lamina, a basally bent left paramere, and the median phallobasal lamina widened and sharply truncated at its apex.
Etymology. The new species is named after one of its collectors, I Var (noun in genitive singular). Variation. Length of body: 9.8-10.2 mm; length of elytra: 7.3-7.5 mm; maximum width: 6.2-6.5 mm.

Tetraserica constanti
Diagnosis. Tetraserica constanti sp. n. is very similar to T. vari sp. n. in the shape of aedeagus but differs by the distinctly shorter median phallobasal lamina and parameres.
Etymology. The new species is named after one of its collectors, J Constant (noun in genitive singular). Description. Length of body: 8.3 mm; length of elytra: 6 mm; maximum width: 4.9 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.64. Ratio of length of metepisternum/metacoxa: 1/1.65. Metatibia short and wide, ratio width/length: 1/2.93; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 20I-K. Habitus: Fig. 20L. Female unknown. Diagnosis. Tetraserica vientianeensis sp. n. differs from the similar T. constanti sp. n. by the basally straight and unbent left paramere, and by the median lamina of phallophase which is not widened at apex.
Etymology. The new species is named with reference to its close occurrence to the city of Vientiane (adjective in the nominative singular). Description. Length of body: 8 mm; length of elytra: 6 mm; maximum width: 5.6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.74. Ratio of length of metepisternum/metacoxa: 1/2.08. Metatibia short and wide, ratio width/length: 1/2.44; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica breviforceps sp. n. differs from all other Tetraserica species with its short parameres and very short median phallobasal lamina, and by the left paramere having a robust (nearly half as long as paramere), subsphaerical, and apically convex dorsal lobe at its base.
Etymology. The name of the new species (noun in apposition) is derived from the combined Latin words brevis (short) and forceps, with reference to the short parameres. Description. Length of body: 9.6 mm; length of elytra: 6.9 mm; maximum width: 6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.55. Ratio of length of metepisternum/metacoxa: 1/1.77. Metatibia short and wide, ratio width/ length: 1/3.12; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica nahaeoensis sp. n. differs from all other Tetraserica species in having a moderately long median phallobasal lamina being narrowed distally, curved dorsally, and having a dorsal tooth at apex; simple left parameres, the shorter right paramere (being one third as long as phallobase), the nearly straight left paramere.
Etymology. The new species is named after the type locality, Na-Haeo (adjective in the nominative singular). eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.5. Ratio of length of metepisternum/metacoxa: 1/1.73. Metatibia short and wide, ratio width/ length: 1/2.93; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica champassakana sp. n. is rather similar to T. nahaeoensis sp. n. in the shape of the aedeagus but differs by the longer right paramere being half as long as phallobase.
Etymology. The new species is named with reference to its occurrence in Champassak province (adjective in the nominative singular). Variation. Length of body: 7.9-8.4 mm; length of elytra: 5.9-6 mm; maximum width: 4.9-5.0 mm.

Tetraserica cattienensis
Diagnosis. Tetraserica cattienensis sp. n. differs from all other Tetraserica species in having a straight or slightly convex posterior margin of the metafemur, small eyes, and the short median phallobasal lamina being half as long as phallobase. From the similar T. bansanpakiana sp. n. and T. margheritae sp. n., T. cattienensis sp. n. differs by the robust spines on the ventral margin of metatibia being subequal in length.

Etymology.
The new species is named after the type locality, Cát Tiên NP (adjective in the nominative singular).
Description. Length of body: 7.6 mm; length of elytra: 6 mm; maximum width: 4.5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.53. Ratio of length of metepisternum/metacoxa: 1/1.5. Posterior margin of metafemur with blunt tooth. Metatibia moderately long and wide, ratio width/length: 1/3.31; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 22E-G. Habitus: Fig. 22H. Female unknown. Diagnosis. Tetraserica multiangulata sp. n. differs by all other Tetraserica species by the blunt tooth at the posterior margin of metafemur, by the long and narrow left paramere, by the median lamina of phallobase being as long or nearly as long as phallobase, and by the left paramere being more than half as long as phallobase; furthermore, the left paramere is split shortly before the apex into two filiform but flattened branches.
Etymology. The name of the new species (adjective in the nominative singular) is derived from the combined Latin words multi (numerous) and angulatus (angled), with reference to the parameres being bent numerous times. Description. Length of body: 9.6 mm; length of elytra: 7.4 mm; maximum width: 6.1 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.53. Ratio of length of metepisternum/metacoxa: 1/1.48. Metatibia short and wide, ratio width/ length: 1/3.25; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica tanahrataensis sp. n. is rather similar to T. mengeana Liu et al., 2014 in the general shape of the aedeagus; the new species differs by lacking trichome-like spines at the base of the right paramere, and the less strongly curved left paramere, which is nearly straight in the basal two thirds. Description. Length of body: 8.6 mm; length of elytra: 6.5 mm; maximum width: 5.3 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.57. Ratio of length of metepisternum/metacoxa: 1/1.38. Metatibia moderately long and wide, ratio width/length: 1/3.43; basal group of dorsal spines of metatibia at first third of metatibial length. Aedeagus: Fig. 23I-K. Habitus: Fig. 23L. Female unknown. Variation. Length of body: 7.6-8.6 mm; length of elytra: 5.5-6.5 mm; maximum width: 4.5-5.3 mm.
Diagnosis. Tetraserica microfurcata sp. n. differs from the similar T. microspinosa sp. n. by the weakly curved, long and filiform left paramere, which is split in apical quarter into two fine branches, as well as the short and slim right paramere being strongly bent at middle.
Etymology. The name of the new species (adjective in nominative singular) is derived from the combined Greek and Latin words micros (small) and furcatus (forked), with reference to the superficial split of the left paramere into two filiform branches.  Description. Length of body: 7.6 mm; length of elytra: 6.0 mm; maximum width: 4.7 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes large, ratio of diameter/interocular width: 0.72. Ratio of length of metepisternum/metacoxa: 1/1.62. Metatibia moderately long and wide, ratio width/ length: 1/3.1; basal group of dorsal spines of metatibia at first third of metatibial length.
Etymology. The new species is named after the type locality, Ulu Lalat Mt (adjective in the nominative singular). Variation. Length of body: 7.3-8.1 mm; length of elytra: 5.4-6.6 mm; maximum width: 4.6-5.0 mm. Female: Antennal club with three antennomeres, as long as remaining antennomeres combined; eyes as large as in male.

Tetraserica infida
Diagnosis. Tetraserica infida sp. n. strongly resembles T. maerimensis Kobayashi, 2018; the new species differs from the latter by the simple left paramere not being divided into dorsal and ventral lobes.
Etymology. The name of the new species (adjective in nominative singular) is derived from the combined Latin prefix in-(non-) and adjective fidus (split), with reference to its unsplit left paramere.
Aedeagus: Fig. 25A-C. Habitus: Fig. 25D. Variation. Length of body: 6.9-8.5 mm; length of elytra: 4.6-5.9 mm; maximum width: 4.1-5.1 mm. Colour may vary from dark brown to nearly entirely yellowish brown with dark head. Female: Antennal club with three antennomeres, as long as remaining antennomeres combined; eyes as large as in male; pygidium flat; robust spines on ventral margin of metatibia subequal in length.
Diagnosis. The new species differs from all other Tetraserica species by the robust metatibial spine in middle of ventral margin being extremely elongate and s-shaped, exceeding distal margin of metatibia.
Etymology. The new species is named after the type locality, Ban San Pakia (adjective in the nominative singular).  eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.44. Ratio of length of metepisternum/metacoxa: 1/1.62. Metatibia short and wide, ratio width/ length: 1/2.83; basal group of dorsal spines of metatibia at first third of metatibial length. Robust spine at middle of ventral margin extremely prolonged and s-shaped, exceeding distal margin of metatibia.
Diagnosis. Tetraserica margheritae sp. n. differs from the externally similar T. bansanpakiana sp. n. by the median phallobasal lamina being narrower and sharply pointed at apex, also by having a dorsal tooth and the left paramere being distinctly shorter than median phallobasal lamina.

Etymology.
The new species is named after Silvia's mother, Margherita (noun in genitive singular). disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.71. Ratio of length of metepisternum/metacoxa: 1/1.55. Metatibia moderately long and wide, ratio width/length: 1/3.4; basal group of dorsal spines of metatibia at first third of metatibial length.

Tetraserica maerimensis
Aedeagus: Fig. 26E-H. Habitus: Fig. 26I. Female unknown. Variation. No significant size variation between types. Diagnosis. Tetraserica soppongana sp. n. differs from all other Tetraserica species in having a long median phallobasal lamina, the right paramere composed of two lobes and having no brush of spines at the base of the right paramere, by the left paramere being composed of two lobes, the right side of phallobase strongly produced, and the dorsal lobe of left paramere as long as ventral one.

Tetraserica longipenis
Remarks. This species was described from Thailand, and is recorded from Myanmar for the first time.
Description. Length of body: 7.8 mm; length of elytra: 5.9 mm; maximum width: 4.8 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.56. Ratio of length of metepisternum/metacoxa: 1/1.64. Metatibia short and wide, ratio width/length: 1/3.08; basal group of dorsal spines of metatibia at first third of metatibial length. Ventral distal spine of metatibia inserted shortly behind middle of ventral margin of metatibia and longer than the long metatarsomere 1.
Aedeagus: Fig. 27E-G. Habitus: Fig. 27H. Female unknown. Diagnosis. Tetraserica giulianae sp. n. is similar to T. angkhangensis Kobayashi, 2017 in shape of the aedeagus, but the new species differs by the basal lobe of left paramere being as long as the ventral lobe, rather than half its length.
Etymology. The new species is named in honour of our friend Giuliana Caturegli (Rome) (noun in genitive singular). Remarks. This species was described from Yunnan, China, and it is recorded from Laos for the first time. Tetraserica gressitti (Frey, 1972), comb. n. Figures 28,48 Tetraserica gressitti Frey, 1972: 198, fig. 60. Redescription. Length of body: 9.3 mm; length of elytra: 6.8 mm; maximum width: 6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.61. Ratio of length of metepisternum/metacoxa: 1/1.79. Metatibia short and wide, ratio width/ length: 1/2.88; basal group of dorsal spines of metatibia at first third of metatibial length.

Tetraserica yaoquensis
Aedeagus: Fig Description. Length of body: 7.5 mm; length of elytra: 5.6 mm; maximum width: 5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.56. Ratio of length of metepisternum/metacoxa: 1/1.8. Metatibia moderately long and wide, ratio width/length: 1/3.91; basal group of dorsal spines of metatibia at first third of metatibial length.

Diagnosis.
Tetraserica loeiensis sp. n. is rather similar to T. matsumotoi Kobayashi, 2017 and T. wapiensis (Frey, 1972) in shape of the aedeagus; the new species differs from both by the dorsal lobe of left paramere which is distinctly longer than the ventral one.
Etymology. The new species is named with reference to its occurrence in Loei province (adjective in the nominative singular). Diagnosis. Tetraserica subrotundata sp. n. is rather similar to T. matsumotoi Kobayashi, 2017 in shape of the aedeagus; the new species differs by the right paramere being bent only once and being slightly wider in lateral view, and the apex of median phallobasal lamina strongly rounded instead of sharply pointed.

Tetraserica subrotundata
Etymology. The name of the new species (adjective in nominative singular) is derived from the combined Latin prefix sub-(under) and adjective rotundatus (rounded), with reference to the shape of the medial apical phallobasal lamina of the aedeagus. Variation. Length of body: 7.5-8.6 mm; length of elytra: 5.8-6.4 mm; maximum width: 5.0-5.9 mm.
Diagnosis. Tetraserica kiriromensis sp. n. is rather similar to T. matsumotoi Kobayashi, 2017 in shape of aedeagus; the new species differs by the right paramere being distinctly shorter than median lamina of phallobase; also the apex of median phallobasal lamina is blunt and curved abruptly dorsally (rather than being straight and sharply pointed).
Etymology. The new species is named after the type locality, Kirirom National Park (adjective in the nominative singular). Description. Length of body: 7.9 mm; length of elytra: 5.6 mm; maximum width: 5.6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.41. Ratio of length of metepisternum/metacoxa: 1/1.79. Metatibia short and wide, ratio width/length: 1/3.08; basal group of dorsal spines of metatibia at first third of metatibial length.

Tetraserica angkorthomensis
Aedeagus: Fig. 30A-C. Habitus: Fig. 30D. Female unknown. Diagnosis. Tetraserica angkorthomensis sp. n. differs from the very similar T. kiriromensis sp. n. by the distinctly shorter right paramere and wider and longer dorsal lobe of left paramere which is directed more distally rather mesally.
Etymology. The new species is named after the type locality, Angkor Thom (adjective in the nominative singular). Description. Length of body: 8.5 mm; length of elytra: 6.5 mm; maximum width: 5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.5. Ratio of length of metepisternum/metacoxa: 1/1.88. Metatibia moderately long and wide, ratio width/ length: 1/3.46; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica pailinensis sp. n. is similar to T. loeiensis sp. n. in shape of aedeagus; T. pailinensis sp. n. differs from the latter by the dorsal lobe of the left paramere being twice as long as the ventral one.
Etymology. The new species is named after the type locality, Pailin (adjective in the nominative singular).
Etymology. The new species is named after the type locality, Ban Huai Po (adjective in the nominative singular). Diagnosis. Tetraserica nussi sp. n. is very similar to T. subrotundata sp. n. in shape of aedeagus, but differs by the much shorter parameres and median phallobasal lamina; the dorsal lobe of left paramere is as long as the ventral one (and not shorter as in T. subrotundata) and the apex of phallobase is strongly asymmetric (dorsal view).

Tetraserica khaosoidaoensis
Diagnosis. Tetraserica khaosoidaoensis sp. n. is very similar to T. nussi sp. n. in shape of the aedeagus; but differs by the distinctly shorter right paramere as well as the only slightly bent right paramere.
Etymology. The new species is named after the type locality, Khao Soi Dao (adjective in the nominative singular). Diagnosis. Tetraserica pahinngamensis sp. n. is very similar to T. wapiensis (Frey, 1972) in shape of aedeagus, differing by the left paramere being simple rather than divided into two long and narrow filiform lobes.
Etymology. The new species is named with reference to its occurrence in the Pa Hin Ngam National Park (adjective in the nominative singular).
Redescription. Length of body: 7.5 mm; length of elytra: 5.5 mm; maximum width: 4.8 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.45. Ratio of length of metepisternum/metacoxa: 1/1.67. Metatibia moderately long and wide, ratio width/length: 1/3.58; basal group of dorsal spines of metatibia at first third of metatibial length.
Remarks. This species was originally described from Laos, and is now reported from Thailand. Description. Length of body: 8.1 mm; length of elytra: 6.6 mm; maximum width: 5.4 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.5. Ratio of length of metepisternum/metacoxa: 1/1.73. Metatibia short and wide, ratio width/ length: 1/3; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 33A-C. Habitus: Fig. 33D. Female unknown. Diagnosis. Tetraserica auriculata sp. n. is similar to T. pailinensis sp. n. in shape of aedeagus, from which it differs by the dorsal lobe of the left paramere being distinctly shorter than the median lamina of phallobase and the right paramere being narrower (in lateral view) and distinctly shorter than median lamina of phallobase. In T. pailinensis sp. n. the dorsal lobe of left paramere is distinctly exceeding the median lamina of phallobase and the right paramere is wider (in lateral view) and a little shorter than median lamina of phallobase.
Etymology. The name of the new species (adjective in nominative singular) is derived from the Latin adjective auriculatus (ear-shaped), with reference to the earshaped median apical lamella of phallobase. Etymology. The species name (adjective in the nominative singular) is derived from the combined Latin words semi (half ) and the species name pingjiangensis, with reference to the similarity to T. pingjiangensis. (Frey, 1972), comb. n.
Redescription. Length of body: 9.8 mm; length of elytra: 6.9 mm; maximum width: 5.6 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area ante-rior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.48. Ratio of length of metepisternum/metacoxa: 1/1.73. Metatibia short and wide, ratio width/length: 1/3.06; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 33I-K. Habitus: Fig. 33L. Remarks. The shape of genitalia of the type specimens of T. midoriae Kobayashi, 2017 is virtually identical with that of the holotype of Tetraserica laotica (Frey, 1972). Two female paratype specimens (1 ♀ "Laos, V 1967 Ban Van Eua/ Paratype Neoserica laotica G. Frey 1971" (CF), 1 ♀ "Laos: ban Van Heue 20km E of Phou-kow-kuei, 1-15V.1965/ Paratype Neoserica laotica G. Frey 1971,) do not belong to this species, as they have both a carinate hypomeron, and are likely to be assigned to the genus Maladera. Diagnosis. Tetraserica pseudoruiliensis sp. n. differs from the similar T. gestroi (Brenske, 1898) by the right paramere which is much less than one third as long as left paramere. The new species differs from T. ruiliensis Liu et al., 2014 by the left paramere being straight rather than bent at the base.

Tetraserica ruiliensis
Etymology. The species name (adjective in the nominative singular) is derived from the combined Greek prefix pseudo-(false) and the species name ruiliensis, with reference to the similarity to T. ruiliensis Liu et al. Description. Length of body: 10 mm; length of elytra: 7.1 mm; maximum width: 5.9 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.59. Ratio of length of metepisternum/metacoxa: 1/1.84. Metatibia short and wide, ratio width/length: 1/2.84; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica semiruiliensis sp. n. differs from the similar T. ruiliensis Liu et al., 2014 by the nearly straight right paramere (lateral view), which is moderately bent at middle (lateral view) in T. ruiliensis. Etymology. The species name (adjective in the nominative singular) is derived from the combined Latin prefix semi-(half ) and the species name ruiliensis, with reference to the similarity to T. ruiliensis Liu et al. Variation. Length of body: 7.6-9.1 mm; length of elytra: 6.0-6.5 mm; maximum width: 4.7-5.0 mm.
Diagnosis. Tetraserica desalvazzai sp. n. is rather similar to T. gestroi, from which the new species differs by the left paramere being straight at base, and both parameres being generally more robust.
Etymology. The new species is named after the collector, RV de Salvazza (noun in genitive singular). Description. Length of body: 8.3 mm; length of elytra: 5.9 mm; maximum width: 4.5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.54. Ratio of length of metepisternum/metacoxa: 1/1.6. Posterior margin of metafemur with blunt tooth. Metatibia moderately long and wide, ratio width/length: 1/3.5; basal group of dorsal spines of metatibia at first third of metatibial length.

Tetraserica phoupaneensis
Aedeagus: Fig. 36A-C. Habitus: Fig. 36D. Female unknown. Diagnosis. Tetraserica phoupaneensis sp. n. is similar to T. vietnamensis (Frey, 1972); the new species differs by the left paramere being as long as phallobase and by the right paramere having a longer basal lobe which is directed distally. In T. vietnamensis the left paramere is only half as long as phallobase, and the right paramere has no basal lobe.

Tetraserica vietnamensis
Aedeagus: Fig. 36E  mere being distinctly wider than the ventral one and slightly curved (dorsal view); also its right paramere is bent in a nearly sharp angle at the middle.
Diagnosis. Tetraserica shanensis sp. n. differs from all other Tetraserica species in having evenly long spines on ventral margin of metatibia, and in the colour of the dorsal surface being yellowish brown.
Etymology. The new species is named with reference to its occurrence in the Shan state (adjective in the nominative singular). wide, ratio width/length: 1/ 3.54; basal group of dorsal spines of metatibia at first third of metatibial length.

Tetraserica semishanensis
Aedeagus: Fig. 38I Diagnosis. Tetraserica allosejugata sp. n. differs from the very similar T. sejugata (Brenske, 1898) by the right paramere being split at the basal third into two narrow branches, while in T. sejugata this split is situated in the apical quarter.
Etymology. The species name (adjective in the nominative singular) is derived from the combined Greek prefix allo-(nearly) and the species name sejugata, with reference to the similarity to T. sejugata (Brenske). Description. Length of body: 8.6 mm; length of elytra: 6.6 mm; maximum width: 5.3 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.57. Ratio of length of metepisternum/metacoxa: 1/1.78. Metatibia short and wide, ratio width/length: 1/3.2; basal group of dorsal spines of metatibia at first third of metatibial length.
Diagnosis. Tetraserica umphangensis sp. n. is rather similar to T. veliformis sp. n.; T. umphangensis sp. n. differs by the right paramere being only half as long as left paramere, and the dorsal lobe of the right paramere, which is distinctly shorter than the ventral lobe. In T. veliformis the right paramere is slightly more than half as long as left paramere, and the split between lobes of the right paramere is deep, the dorsal lobe is as long as the ventral lobe.

Tetraserica pingjiangensis
Diagnosis. Tetraserica bolavensensis sp. n. differs from the similar T. latefemorata Kobayashi, 2017 by the right paramere being half as long as left paramere and the deep split between lobes of right parameres; also the dorsal lobe is not reduced in size.
Etymology. The new species is named after the type locality, Bolavens Plateau (adjective in the nominative singular).
Description. Length of body: 8.9 mm; length of elytra: 6.6 mm; maximum width: 5.5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.5. Ratio of length of metepisternum/metacoxa: 1/1.74. Metatibia short and wide, ratio width/ length: 1/2.81; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 41I-K. Habitus: Fig. 41L. Female unknown. Diagnosis. Tetraserica nakaiensis sp. n. differs from the similar T. bolavensensis sp. n. by the left paramere being at middle distinctly widened and distinctly longer than the median phallobasal lamina. In T. bolavensensis the left paramere is narrow in the middle (lateral view) and only a little longer than the median phallobasal lamina.
Diagnosis. Tetraserica petrpacholatkoi sp. n. differs from T. constanti sp. n. and T. vientianeensis sp. n. by the left paramere being half as long as the phallobase.

Tetraserica senohi
Redescription. Length of body: 8.4 mm; length of elytra: 6.6 mm; maximum width: 5.4 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.54. Ratio of length of metepisternum/metacoxa: 1/1.68. Metatibia short and wide, ratio width/length: 1/3.21; basal group of dorsal spines of metatibia at first third of metatibial length.
Etymology. The new species is named after one of its collectors, M Riha (noun in genitive singular).
Description. Length of body: 6.3 mm; length of elytra: 4.5 mm; maximum width: 3.8 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes moderately large, ratio of diameter/interocular width: 0.62. Ratio of length of metepisternum/metacoxa: 1/1.55. Metatibia short and wide, ratio width/length: 1/3.1; basal group of dorsal spines of metatibia at first third of metatibial length.
Female unknown. Diagnosis. Tetraserica doipuiensis sp. n. differs from the similar T. champassakana sp. n. by the left paramere lacking the blunt lateral tooth before the apex and the right paramere being as long as medial phallobasal lamina.
Etymology. The new species is named after the type locality, Mt Doi Pui (adjective in the nominative singular).
Description. Length of body: 8.8 mm; length of elytra: 6.3 mm; maximum width: 5.3 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.54. Ratio of length of metepisternum/metacoxa: 1/1.75. Metatibia moderately long and wide, ratio width/length: 1/3.5; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 44A-C. Habitus: Fig. 44D. Female unknown. Diagnosis. Tetraserica doiphukhaensis sp. n. differs from all other Tetraserica in having a very short median phallobasal lamina, by having the left paramere short and stout, and a simple right paramere without a dorsal lobe.
Etymology. The new species is named after the type locality, Doi Phu Kha NP (adjective in the nominative singular).
Description. Length of body: 10 mm; length of elytra: 7.4 mm; maximum width: 6.1 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.52. Ratio of length of metepisternum/metacoxa: 1/1.7. Posterior margin of metafemur with sharp hook. Metatibia short and wide, ratio width/length: 1/3.17; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 44E-G. Habitus: Fig. 44H. Female unknown. Diagnosis. Tetraserica kontumensis sp. n. differs from all other Tetraserica species by having a short and wide left paramere, split into a dorsal hook and a basal filiform branch which is also turned dorsally.
Etymology. The new species is named with reference to its occurrence in the Kon Tum province (adjective in the nominative singular).
Remarks. The correct GPS coordinates of the type locality are 15°14'26.04"N, 107°44'11.61"E. Description. Length of body: 7.8 mm; length of elytra: 5.6 mm; maximum width: 5 mm. Surface of labroclypeus and disc of frons glabrous. Smooth area anterior to eye twice as wide as long. Eyes small, ratio of diameter/interocular width: 0.52. Ratio of length of metepisternum/metacoxa: 1/1.56. Metatibia moderately long and wide, ratio width/length: 1/3.75; basal group of dorsal spines of metatibia at first third of metatibial length.
Aedeagus: Fig. 44I-K. Habitus: Fig. 44L. Female unknown. Diagnosis. Tetraserica semidamadiensis sp. n. is very similar to T. damadiensis Liu et al., 2014 but the new species differs by the dorsolateral tooth being situated at the basal third of the right paramere, and by the wider right paramere (lateral view).
x x T. falciformis sp. n.
x Appendix 1