Remarkable Species Diversity of the Leafhopper Genus Xestocephalus (Hemiptera: Cicadellidae: Aphrodinae) in Thailand

Simple Summary Thailand, a country on the Indochinese peninsula in Southeast Asia, is part of a biodiversity hot spot that harbors a large number of endemic species. The insect fauna remains poorly known, but a recent bioinventory has provided many new specimens for study. We review the common, widespread leafhopper genus Xestocephalus from Thailand and provide detailed morphological descriptions (the main evidence distinguishing species) and distributions of all species. Seventeen species were recognized, including twelve new species and four species recorded in Thailand for the first time. Abstract Xestocephalus Van Duzee is among the most common and widespread genera of Cicadellidae in the temperate and tropical regions of the world. In the present study, 205 specimens of the genus Xestocephalus were collected in Thailand, whereas only a single species of the genus was recorded previously using Malaise trap field sampling, studied by comparative morphology. Seventeen species were recognized, including twelve new species: X. binarius sp. nov., X. chrysanthemum sp. nov., X. cowboyocreus sp. nov., X. densprint sp. nov., X. dimiprocessus sp. nov., X. exproiecturus sp. nov., X. gracilus sp. nov., X. limpidissimus sp. nov., X. malleus sp. nov., X. nonattribus sp. nov., X. recipinams sp. nov., and X. tenusis Liang sp. nov. Four species were recorded in Thailand for the first time: Xestocephalus abyssinicus Heller and Linnavuori, Xestocephalus asper Linnavuori, Xestocephalus ishidae Matsumura, and Xestocephalus toroensis Matsumura. Detailed morphological descriptions of all 17 species are given; photographs of external habitus and male genitalia of the species from Thailand are provided. A checklist of species of the genus is also given, and a key to all Thailand Xestocephalus species is also provided.


Introduction
Thailand, located on the Indochinese peninsula in Southeast Asia, is part of a biodiversity hot spot that harbors a large number of endemic species, estimated to comprise a significant proportion of the total species known worldwide [1]. The rich diversity of insect taxa may be explained in part by the country's widespread tropical seasonal forests and floristic composition. However, until recently, few studies of Thai insects have been conducted. A recent biodiversity inventory project focused on insects, led by scientists at the University of Kentucky (USA) and Queen Sirikit Botanical Garden (Thailand), yielded large numbers of specimens from protected areas throughout the country [2]. A previous study of these samples revealed numerous new and apparently endemic genera and species of many different insect groups, including leafhoppers [3][4][5][6][7][8].
Leafhoppers (Cicadellidae) comprise the largest family of Hemiptera and are one of the largest families of plant-feeding insects, with nearly 24,000 described species in over   Figure 49a-c [24].
Redescription. Length: ♂2.7-2.9 mm, ♀2.7-2.9 mm. Coloration includes two morphs: Morph 1 is dark brown with grayish-white markings ( Figure 1D-F): Morph 2 is pale ochraceous with gray markings ( Figure 1A-C). Vertex with three round grayish-white spots on anterior margin and four grayish-white spots on submargin, discal area with a grayish-white longitudinal line on each side of brown midline and narrower transverse grayish-white band posteriorly, a small grayish-white spot adjacent to basal angles of eyes. Face pale brown, with marginal arcuate band dark brown. Pronotum dark-brown, with several distinct cream spots at anterior margin and submargin. Scutellum dark-brown  Redescription. Length: ♂ 2.7-2.9 mm, ♀ 2.7-2.9 mm. Coloration includes two morphs: Morph 1 is dark brown with grayish-white markings ( Figure 1D-F): Morph 2 is pale ochraceous with gray markings (Figure 1A-C). Vertex with three round grayishwhite spots on anterior margin and four grayish-white spots on submargin, discal area Male genitalia. Pygofer in lateral view narrowed toward round caudal margin, slightly higher than long, posteroventral margin slightly curved inward, with a tooth-like process on inner surface arising on the ventral margin and extending posterodorsally, macrosetae arranged in preapical vertical band, posterior margin with many tiny setae. Valve transverse, much wider than long, with parallel anterior and posterior margin. Subgenital plate broad linguiform, apical margin rounded, apical 2/3 of lateral margin curved inward, with two rows of macrosetae. Style slender, S-shaped, apex enlarged with short, acute preapical heel, apical margin evenly convex, without teeth. Connective crossshaped, lateral arms extended anterolaterad, median anterior lobe slender and longer than lateral arms. Aedeagus symmetrical, shaft slightly longer than atrium, anterior margin relatively straight in lateral view, anterior margin shallowly concave with pair of dentate flanges on each side, abruptly tapering apically in lateral view. Gonopore subapical on caudal margin.
Female. Sternite VII nearly twice as wide as long, posterior margin slightly concave with slight V-shaped medial notch. Second valvulae with preapical ventral angle obtuse. Third valvula with preapical emargination slightly concave.
Remarks. X. asper was described by Linnavuori [64] based on one male and two female specimens from the Congo. Later, he also described X. asper pseudoguttulatus for a variant with a smaller body and blunter crown [24]. This species is similar to X. subfusculus Melichar but differs from the latter in having the lateral lamellae of the aedeagus narrow. Different specimens examined from Chiang Mai, Thailand, appear to correspond to both subspecies recognized by Linnavuori, but specimens from Chaiyaphum and Nakhon Nayok correspond only to the nominotypical subspecies. The aedeagus of specimens from Thailand differs slightly from specimens from Africa illustrated by Linnavuori [64] in having the lateral flange somewhat narrower in posterior view. We interpret this variation as intraspecific but a study of more specimens from both Africa and Southeast Asia will be necessary to determine the taxonomic significance of such variation.
Redescription. Length: ♂ 2.3-2.5 mm, ♀ 2.8-2.9 mm. Light brown with numerous cream-colored patches and brown cloudy markings all over. Vertex brown with three small whitish spots, two ocelli respectively situated in the white dot on each side; two obscure short pale stripes next to each eye. Face brown and immaculate. Pronotum mottled with many irregular small pale spots; anterior margin, lateral angles ground-color Redescription. Length: ♂2.3-2.5 mm, ♀2.8-2.9 mm. Light brown with numerous cream-colored patches and brown cloudy markings all over. Vertex brown with three small whitish spots, two ocelli respectively situated in the white dot on each side; two obscure short pale stripes next to each eye. Face brown and immaculate. Pronotum mottled with many irregular small pale spots; anterior margin, lateral angles ground-color brown. Scutellum mottled with two large diverging darker patches near basal angles, apical area lighter, with a crescent-like marking and neighboring four distinct cream-colored speckles. Forewings shiny light brown, with many elongate hyaline patches near apical portion and brown cloudy markings along costal margin; veins surrounded with shadows or whitish markings. Ventral surface and legs with uniform brown.
Male genitalia. Pygofer in lateral view higher than its length, furnished with approximately 12-15 macrosetae on posterior half, with caudal margin dentate and several distinct notches along the posteroventral margin. Internal process of pygofer small and obtuse-angled, directed ventrad. Valve short and trapezoidal. Subgenital plate moderately long, curved gradually and slightly dorsad, broadly rounded apically in lateral view, broad basally and then slightly narrowed to apex in ventral view, with two or three rows of macrosetae. Style slender, S-shaped, apical dilation of apophysis narrowly boot-shaped, without teeth. Connective cross-shaped, side arms folded anterad. Aedeagus with shaft straight, lightly longer than dorsal apodeme, slightly asymmetrical with longitudinal lamella on either side and apex expanded and diamond-shaped in ventral aspect. Gonopore subapical and ventral.
Remarks. X. guttulatus was described by Motschulsky [53] as Deltocephalus guttulatus based on one male specimen from Sri Lanka. Matsumura [66] described the same species as Xestocephalus guttulatus based on one male and one female from Japan. Melichar [67] suggested that the latter is a synonym of the former but used the name Xestocephalus guttatus. After that, many authors included Xestocephalus guttatus in catalogues of Cicadellidae [28,37,59,[61][62][63][66][67][68][69][70][71][72][73][74][75][76][77][78][79]81]. Linnavuori [24] redescribed this species and illustrated the male genitalia. The figures of male genitalia provided by Ishihara [30] and Anufriev and Emeljanov [82] indicate that these authors misidentified the species. X. guttulatus is morphologically very similar to X. asper, with only very slight differences in the aedeagus (e.g., shaft and dorsal apodeme broader in lateral view and lateral flange smooth rather than minutely serrate) and style (distal "foot" more elongated). Here, X. guttulatus and X. asper are tentatively retained as separate valid species, but a comparative study of additional specimens from throughout the range is needed to confirm their status.  Redescription. Length: ♂2.3-2.5 mm, ♀2.4-2.6 mm. Yellowish with numerous whitish cloudy markings. Crown relatively blunt, covered with several faint pale longitudinal stripes between eyes. Vertex dull yellow with a brownish irregular line extending from near apex to eye, curving around ocelli; two obscure whitish spots next to each eye. Face yellowish and immaculate. Pronotum mottled with two rows small pale spots; anterior margin, lateral angles ground-color fuscous. Scutellum mottled with two large diverging darker patches near basal angles, apical area lighter, with a crescent-like marking and neighboring four distinct pale speckles. Forewings shiny yellow throughout, with many elongate hyaline patches, especially along costal margin and apical portion; veins surrounded with shadows or whitish markings. Ventral surface and legs with uniform yellowish. Insects 2021, 12, x FOR PEER REVIEW 12 of 52   [32].
Redescription. Length: ♂ 2.3-2.5 mm, ♀ 2.4-2.6 mm. Yellowish with numerous whitish cloudy markings. Crown relatively blunt, covered with several faint pale longitudinal stripes between eyes. Vertex dull yellow with a brownish irregular line extending from near apex to eye, curving around ocelli; two obscure whitish spots next to each eye. Face yellowish and immaculate. Pronotum mottled with two rows small pale spots; anterior margin, lateral angles ground-color fuscous. Scutellum mottled with two large diverging darker patches near basal angles, apical area lighter, with a crescent-like marking and neighboring four distinct pale speckles. Forewings shiny yellow throughout, with many elongate hyaline patches, especially along costal margin and apical portion; veins surrounded with shadows or whitish markings. Ventral surface and legs with uniform yellowish. Male genitalia. Pygofer in lateral view higher than its length, narrowed toward round caudal margin with many macrosetae on posterior margin, caudal margin dentate with several distinct notches; process tooth-like and directed ventrad. Valve short and trapezoidal. Subgenital plate broad, linguiform, apical portion rounded, lateral margins of apex 2/3 slightly curved inwards, with two rows of macrosetae. Style slender, Sshaped, apex enlarged with prominent preapical heel, curved laterad, without teeth, preapical lobe developed. Aedeagus with shaft short, slightly longer than preatrium, slightly concave with an indistinct elongate flange on each side of anterior surface straight in lateral view, posterior margin nearly straight in lateral view with a slight flange on each side, abruptly narrowed apically, apical margin round in caudal view. Gonopore subapical on caudal margin.
Remarks. X. ishidae was described by Matsumura [59] based on one male specimen from Japan. Kamitani [32] examined the holotype and redescribed it, illustrated the external habitus, and was the first to illustrate the male genitalia. The examined specimens from Thailand are slightly different from the holotype in having the aedeagal shaft slightly concave on the anterior margin with two shallow flanges. This species is similar to X. kuyanianus Matsumura [32] but distinguished by aedeagal shaft straight, head and thoracic nota with markings, and with 8-10 macrosetae on the genital plate (aedeagal shaft slight curved, head and thoracic nota without markings, and with 20 macrosetae on the genital plate in X. kuyanianus).

3.3.4.
Xestocephalus gracilus sp. nov. Male genitalia. Pygofer in lateral view higher than its length, narrowed to round caudal margin, with approximately 8 macrosetae on posterior half; internal process bluntly rectangular and directed ventrad. Valve short and trapezoidal. Subgenital plate broad, linguiform, apex rounded, lateral margins of apical 2/3 slightly curved inwards, with 2 rows of macrosetae. Style slender, S-shaped, with apical dilation of apophysis large thorn-shaped, with numerous scattered marginal and submarginal teeth, tapered to a point, apical 1/2 bent. Aedeagus with dorsal apodeme 1/2 times as long as shaft, shaft moderately long, with anterior margin straight in lateral view, tapering to apex gradually. Gonopore ventral, situated near basal 1/2 of shaft. Distribution. Thailand (Kamphaeng Phet) ( Figure 27). Etymology. The specific epithet is a Latin adjective referring to the slender aedeagus.

Remarks.
The new species is similar to X. punctulatus Carvalho and Cavichioli [83] but can be distinguished from the latter by pygofer with internal process bluntly rectangular, the straight aedeagus with robust base, and the denticuli on the subapex of the styles (pygofer with internal process triangular, the straight aedeagus slight robust at middle in X. punctulatus).

3.3.5.
Xestocephalus nonattribus sp. nov. Figure 5D-L, Figure 7A-J, Figure 24D-F, and Figure 25D1-F3. Description. Length: ♂2.6-2.8 mm, ♀2.7-2.8 mm. Color pattern with two different morphs, female color darker than male; one generally yellowish except forewings with brown cloudy markings at apex ( Figure 5D-F,J-L); the other light brown with numerous pale patches all over dorsum ( Figure 5G-I). Latter morph has crown covered with several pale obscure stripes between eyes. Vertex with a brownish irregular line extending from near apex to eye, curving around ocelli. Face yellowish and immaculate. Pronotum brown, with many irregular small pale spots evenly distributed. Scutellum brown, apical area light, with crescent-like marking and two distinct dumbbell-shaped pale spots. Forewings shiny brown, evenly covered with many elongate hyaline patches; veins surrounded with shadows. Ventral surface and legs uniform light yellow. Male genitalia. Pygofer in lateral view higher than its length, narrowed to round caudal margin, with approximately 8 macrosetae on posterior half; internal process bluntly rectangular and directed ventrad. Valve short and trapezoidal. Subgenital plate broad, linguiform, apex rounded, lateral margins of apical 2/3 slightly curved inwards, with 2 rows of macrosetae. Style slender, S-shaped, with apical dilation of apophysis large thorn-shaped, with numerous scattered marginal and submarginal teeth, tapered to a point, apical 1/2 bent. Aedeagus with dorsal apodeme 1/2 times as long as shaft, shaft  Distribution. Thailand (Kamphaeng Phet) ( Figure 27). Etymology. The specific epithet is a Latin adjective referring to the slender aedeagus.

Remarks.
The new species is similar to X. punctulatus Carvalho and Cavichioli [83] but can be distinguished from the latter by pygofer with internal process bluntly rectangular, the straight aedeagus with robust base, and the denticuli on the subapex of the Male genitalia. Pygofer in lateral view higher than its length, with many macrosetae on posterior margin, internal process absent. Valve short and trapezoidal. Subgenital plate extending posteriorly farther than pygofer apex, broad, linguiform, basal half horizontal and apical half vertical, with apices broadly rounded in lateral view, with a row of macrosetae and serially arranged lateral microsetae. Style slender, S-shaped, with subapical part of apophysis slightly broadened, without preapical heel; elongated and tapered gradually to apex, texture of apical part irregularly reticulate. Connective cross-shaped, the side arms folded downward. Aedeagus with preatrium developed, shaft strongly compressed, slightly longer than preatrium, anterior margin straight, posterior margin rounded in profile, narrowed to rounded apex in lateral aspect, acuminate in posterior view. Gonopore slit-like near basal 1/3 of shaft. styles (pygofer with internal process triangular, the straight aedeagus slight robust at middle in X. punctulatus).     Distribution. Thailand (Chiang Mai, Suphanburi, Loei, Chaiyaphum, Prachuab, Nakhon Nayok, Kanchanaburi) ( Figure 27).
Etymology. The species name is a Latin adjective, which refers to the aedeagal shaft without processes.
Remarks. Comparison of male specimens from different localities in Thailand suggests that this species is somewhat variable in coloration and male genitalia. The discrepancy in color may be a result of preservation in alcohol, but specimens from different localities also exhibit slight variations in the shape of the aedeagus in lateral view (cf. Figure 7E,F). These forms intergrade, so we consider them to belong to a single species.
The new species is similar to X. medius Linnavuori in aedeagus but distinguished by the apically slender apophysis of the styles (thickened apophysis in X. medius).
3.3.6. Xestocephalus binarius sp. nov. Description. Length: ♂3.5-3.8 mm, ♀3.9-4.0 mm. General color yellowish with brown cloudy markings. Crown relatively blunt and covered with several obscure dark spots between eyes. Vertex with a brownish irregular line extending from near apex to eye, curving around ocelli. Face cream-colored and immaculate. Pronotum yellowish mottled with brown irregular cloudy markings. Scutellum mottled with two large diverging brown patches near basal angles, apical area lighter, with a crescent-like marking, neighboring two distinct dumbbell-shaped pale speckles. Forewings shiny yellow and hyaline, with brown cloudy markings along costal margin and apical portion especially, veins with or without white segments. Ventral surface and legs uniform dull yellow. Female color pattern as in male, but ground-color of crown and vertex cream-colored, which makes the color pattern more distinct.
Male genitalia. Pygofer in lateral view longer than its height, with many macrosetae on posterior half, caudal margin dentate; internal process tooth-like, directed ventrad. Valve short and rectangular. Subgenital plate extending posteriorly farther than pygofer apex, narrow, triangular, gradually tapered in apical 1/2, with a row of macrosetae in middle and several microsetae along inner margins. Style slender, S-shaped, apical dilation of apophysis elongate boot-shaped, strongly curved, without teeth, apex acuminate. Connective cross-shaped, the side arms folded downward. Aedeagus with dorsal apodeme short, shaft moderately long, sinuate, gradually tapered to apex, with pair of slender processes arising apically and extended basolaterad, 1/3 length of shaft. Gonopore ventral, situated near basal 1/3 of shaft.
Female Distribution. Thailand (Chiang Mai) ( Figure 27). Etymology. The species name is a Latin adjective, which refers to the aedeagal shaft with two short processes.
Remarks. This species can be identified by the aedeagus with a single pair of apical processes; all other species with two pairs of processes or no process arising apically or subapically.  Description. Length: ♂ 3.6-3.8 mm, ♀ 3.9-4.1 mm. General color yellowish with brown cloudy markings. Crown relatively pointed and covered with several obscure dark spots between eyes. Vertex with a light brown irregular line extending from near apex to eye, curving around ocelli. Face cream-colored and immaculate. Pronotum yellowish mottled with light brown irregular cloudy markings. Basal triangles of scutellum dull orange with brown crescent-like margins. Forewings shiny yellow and hyaline, with brown cloudy markings along costal margin and apical portion especially, veins with or without intermittent white segments. Ventral surface and legs uniform dull yellow. Female color slightly darker than male.   Figure 10A-F, Figure 24H, and Figure 25H1-H3. Description. Length: ♂3.6-3.8 mm, ♀3.9-4.1 mm. General color yellowish with brown cloudy markings. Crown relatively pointed and covered with several obscure dark spots between eyes. Vertex with a light brown irregular line extending from near apex to eye, curving around ocelli. Face cream-colored and immaculate. Pronotum yellowish mottled with light brown irregular cloudy markings. Basal triangles of scutellum dull orange with brown crescent-like margins. Forewings shiny yellow and hyaline, with brown cloudy markings along costal margin and apical portion especially, veins with or without intermittent white segments. Ventral surface and legs uniform dull yellow. Female color slightly darker than male. Male genitalia. Pygofer in lateral view longer than height, lobe with approximately 22 macrosetae on posterior half, with caudal margin dentate. Internal process of pygofer elongate, thornlike, directed ventrad. Valve short and rectangular. Subgenital plate narrow, triangular, gradually tapered in apical 1/2, with 2 or 3 macrosetae in middle and several microsetae along inner margins. Style slender, S-shaped, apical dilation of apophysis elongate boot-shaped, strongly curved and tapered gradually, without distinct teeth. Connective cross-shaped, side arms folded downward. Aedeagus with shaft much longer than apodeme, anterior margin straight and posterior margin protruded at middle, with a row of basal denticles on each side and two pairs of slender apical processes directed lateroventrally, upper processes longer than lower ones. Gonopore ventral, situated near basal 1/3 of shaft. Male genitalia. Pygofer in lateral view longer than height, lobe with approximately 22 macrosetae on posterior half, with caudal margin dentate. Internal process of pygofer elongate, thornlike, directed ventrad. Valve short and rectangular. Subgenital plate narrow, triangular, gradually tapered in apical 1/2, with 2 or 3 macrosetae in middle and several microsetae along inner margins. Style slender, S-shaped, apical dilation of apophysis elongate boot-shaped, strongly curved and tapered gradually, without distinct teeth. Connective cross-shaped, side arms folded downward. Aedeagus with shaft much longer than apodeme, anterior margin straight and posterior margin protruded at middle, with a row of basal denticles on each side and two pairs of slender apical processes directed lateroventrally, upper processes longer than lower ones. Gonopore ventral, situated near basal 1/3 of shaft. Distribution. Thailand (Chiang Mai) ( Figure 27). Etymology. The species name is the Latin word "densprint", which refers to the base of the aedeagal shaft with two rows of odontoid processes.
Remarks. The new species is similar to X. binatus Cai and He [84] in aedeagal structure but distinguished by the aedeagal shaft with apical processes shorter than 2/5 length of shaft, with a row of basal denticles on each side (aedeagus with apical processes equal to 1/2 length of shaft, without a vrow of basal denticles on each side in X. binatus).   [32]. Redescription. Length: ♂2.7-2.9 mm, ♀3.7-3.9 mm. General color yellowish with brown cloudy markings. Crown covered with two obscure semicircular brown markings between eyes. Vertex with intermittent brownish line extending from near apex to eye, curving around ocelli. Face yellow and immaculate. Pronotum yellowish mottled with obscure brown cloudy markings, especially along lateral margins. Scutellum yellow, mottled with two diverging dark patches near basal angles, apical area light, with a crescent-like marking. Forewings yellow and hyaline, with brown cloudy markings along costal margin and apical portion especially, shadowed along veins. Ventral surface and legs uniform yellow.
Male genitalia. Pygofer in lateral view as long as high, gradually narrowed to round caudal margin, with many macrosetae on posterior half; internal process tooth-like and directed ventrad. Valve short and trapezoidal. Subgenital plate narrow, triangular, gradually tapered in apical 1/2, with 2 or 3 macrosetae near middle and several short microsetae along inner margins. Style slender, S-shaped, apical dilation of apophysis relatively broad, boot-shaped, strongly curved and tapering, and basal 1/3 with slight incision on posterior margin, without distinct teeth. Connective cross-shaped, the side arms folded downward. Aedeagus with dorsal apodeme 1/2 as long as shaft; shaft moderately long, anterior margin straight and posterior margin slightly protruded at middle, with two pairs of relatively long, slender apical processes directed lateroventrally, upper processes shorter than lower ones. Gonopore ventral, situated near basal 1/2 of shaft.
Female   Remarks. X. toroensis was described by Matsumura [59] based on three male and one female specimens from Taiwan, China. Kamitani [32] redescribed and illustrated the genitalia for the first time. It resembles X. binatus Cai and He [84] but differs in having the upper processes of the aedeagus shorter than the lower ones (upper processes longer than lower ones in X. binatus).
3.3.9. Xestocephalus chrysanthemum sp. nov. italia for the first time. It resembles X. binatus Cai and He [84] but differs in having the upper processes of the aedeagus shorter than the lower ones (upper processes longer than lower ones in X. binatus).
3.3.9. Xestocephalus chrysanthemum sp. nov.  Description. Length: ♂ 2.9-3.0 mm, ♀ 3.1 mm. General color yellowish with brown cloudy markings. Crown covered with two semicircular brown markings between eyes. Vertex with intermittent brownish line extending from near apex to eye, curving around Description. Length: ♂2.9-3.0 mm, ♀3.1 mm. General color yellowish with brown cloudy markings. Crown covered with two semicircular brown markings between eyes. Vertex with intermittent brownish line extending from near apex to eye, curving around ocelli. Face cream-colored and immaculate. Pronotum yellowish mottled with dense brown cloudy markings especially along lateral margins. Each angle of scutellum mottled with crescent-like marking and shadow. Forewings shiny yellow and hyaline, with brown cloudy markings along costal margin and apical portion especially along veins. Ventral surface and legs uniform faint yellow.
Male genitalia. Pygofer in lateral view as long as high, gradually narrowed to round posterior margin, with many macrosetae on posterior half; internal process tiny, tooth-like, directed ventrad. Valve short and trapezoid. Subgenital plate narrow, triangular, gradually tapered in apical 1/2, with 3 macrosetae in middle and several short microsetae along inner margins. Style slender, S-shaped, apical dilation of apophysis large, boot-shaped, strongly curved, tapered, basal 1/3 of posterior margin with slight incision, apical margin irregular but without distinct teeth. Connective cross-shaped, the side arms folded downward.
Aedeagus with dorsal apodeme 1/2 as long as shaft; shaft moderately long, curved dorsad and tapering gradually, with two pairs of apical processes directed lateroventrally, upper processes 1/2 as long as lower ones and curved anterad. Gonopore ventral, situated near basal 1/2 of shaft.
Female Distribution. Thailand (Nakhon Si, Kamphaeng, Chiang Mai) ( Figure 27). Etymology. The species name "chrysanthemum" is a plant genus name and Latin noun and refers to the processes of the resemblance of the aedeagal shaft to Chrysanthemum petals.
Remarks. The new species is similar to X. toroensis Matsumura [32] but differs in having the aedeagal shaft distinctly curved with the upper pair of distal processes curved anterad (aedeagal shaft slightly curved with two pairs of distal processes straight in X. toroensis).

3.3.10.
Xestocephalus tenusis sp. nov. Figure 13A-C, Figure 14A-F, Figure 24K, and Figure 26B1-B3. Description. Length: ♂3.6-3.7 mm, ♀3.8-4.0 mm. Yellowish with brown cloudy markings. Crown relatively pointed and covered with several obscure dark spots between eyes. Vertex with brownish irregular line extending from near apex to eye, curving around ocelli. Face yellowish and immaculate. Pronotum yellowish mottled with brown irregular cloudy markings especially along lateral margins. Scutellum mottled with brown irregular cloudy markings near basal angles, apical area lighter, with a crescent-like marking. Forewings shiny yellow and hyaline, with brown cloudy markings along costal margin and apical portion especially, shadowed along veins. Ventral surface and legs uniform yellowish.
Male genitalia. Pygofer in lateral view longer than high, with approximately 19 macrosetae on posterior half; internal process triangular, directed ventrad. Valve short and trapezoidal. Subgenital plate narrow, triangular, gradually tapered in apical 1/2, furnished with 3 macrosetae in apical 2/3 and several short macrosetae along inner margins. Style slender, S-shaped, apical dilation of apophysis broad, boot-shaped, evenly curved, tapered gradually, basal 1/3 of distal margin with slight incision, without distinct teeth. Connective cross-shaped, the side arms folded downward. Aedeagus with dorsal apodeme 1/2 as long as shaft; shaft moderately long, slightly curved anteriorly and broadened medially, tapering to blunt apex in lateral and ventral aspect, with two pairs of long, slender, nearly straight apical processes directed ventroposteriorly, upper processes as long as lower ones. Gonopore ventral, situated near midlength of shaft.
Material examined. Holotype   Male genitalia. Pygofer in lateral view longer than high, with approximately 19 macrosetae on posterior half; internal process triangular, directed ventrad. Valve short and trapezoidal. Subgenital plate narrow, triangular, gradually tapered in apical 1/2, furnished with 3 macrosetae in apical 2/3 and several short macrosetae along inner margins. Style slender, S-shaped, apical dilation of apophysis broad, boot-shaped, evenly curved, tapered gradually, basal 1/3 of distal margin with slight incision, without distinct teeth. Connective cross-shaped, the side arms folded downward. Aedeagus with dorsal apodeme 1/2 as long as shaft; shaft moderately long, slightly curved anteriorly and broadened medially, tapering to blunt apex in lateral and ventral aspect, with two pairs of long, slender, nearly straight apical processes directed ventroposteriorly, upper processes as long as lower ones. Gonopore ventral, situated near midlength of shaft.  Distribution. Thailand (Chiang Mai, Chaiyaphum) ( Figure 27). Etymology. The species name is a Latin word meaning slender, which refers to the two pairs of slender processes of the aedeagal shaft.
Remarks. This species resembles X. binatus Cai and He [84] but can be identified by the two pairs of equally long, straight, and slender apical processes on the aedeagal shaft (upper processes shorter than lower ones in X. binatus).
3.3.11. Xestocephalus exproiecturus sp. nov. Figure 13D-F, Figure 15A-F, Figure 16A-F, Figure 24L, and Figure 26C1-C3. Description. Length: ♂2.8-3.0 mm, ♀3.1-3.2 mm. General color brownish with numerous cream-colored spots. Crown covered with four cream-colored spots and posterior margin cream-colored between eyes. Vertex with three small whitish spots, ocelli situated in white dots on each side; each side with short whitish stripe connecting ocellus and eye. Face light brown and immaculate. Pronotum brown mottled with evenly distributed cream-colored spots. Scutellum brown, with a crescent-like marking flanked by four distinct pale speckles. Forewings shiny yellow and hyaline, with brown cloudy markings along costal margin and apical portion especially, veins intermittently white and brown. Ventral surface and legs uniform pale brown.
Male genitalia. Pygofer in lateral view longer than high, gradually narrowed to round caudal margin, with many macrosetae on posterior half; internal process tooth-like and directed ventrad. Valve short and trapezoidal. Subgenital plate triangular, broadened at base and narrowing to apex, with 2-3 macrosetae near middle and several microsetae along inner margin. Style slender, S-shaped, apical dilation of apophysis relatively short and broad, boot-shaped, apical margin evenly convex, without teeth, apex evenly tapered. Connective cross-shaped, the side arms folded downward. Aedeagus with dorsal apodeme slightly longer than half shaft length, shaft straight. Posterior margin irregularly curved in lateral view, abruptly narrowed at apical 1/3, with paired long, straight apical and subapical processes directed lateroventrally, apical processes as long as subapical ones. Gonopore ventral, situated near midlength of shaft.
Female. Sternite VII posterior margin slightly convex with slight median notch. Sec-  Distribution. Thailand (Phetchabun, Nakhon Nayok, Lampang, Chanthaburi) ( Figure 27). Etymology. The species name combines the Latin words "ex" + "proiecturus", which refers to the separation of the base of two pairs of processes from the aedeagal shaft.
Remarks. The new species is similar to X. tenusis sp. nov. but differs in having the aedeagal shaft abruptly narrowed at the apical 1/3 in lateral view and in having the bases of the two pairs of shaft processes distinctly separated (aedeagus slightly curved anteriorly and broadened medially, tapering to blunt apex, with bases of two pairs of shaft processes distinctly close-set in X. tenusis).  several pale obscure spots between eyes. Vertex with a brownish irregular line extending from near apex to eye, curving around ocelli. Face cream-color, immaculate extending to vertex. Pronotum brown, two elongated pale spots in middle and two round pale spots next to lateral margin, respectively. Scutellum brown, apical area lighter with a crescent-like marking. Forewings shiny yellow, with many elongate hyaline patches and brown cloudy markings all over; veins surrounded with shadows. Ventral surface and legs uniform light yellow.

Xestocephalus abyssinicus
Male genitalia. Pygofer in lateral view higher than long, furnished with approximately 15-20 macrosetae on posterior half, caudal margin dentate and several distinct notches along ventral margin posterior margin. Internal process of pygofer tooth-like and directed ventrad. Valve short and trapezoidal. Subgenital plate broad, linguiform, apical portion rounded, lateral margins of apex 2/3 slightly curved inwards, with group of macrosetae near base and several rows of hairlike setae at elevation near inner margin. Style slender, S-shaped, subapical dilation of apophysis indistinct, preapical heel poorly developed, apex tapered, without teeth. Connective cross-shaped, the side arms folded downward. Aedeagus symmetrical basal apodeme shorter and much slender than shaft in lateral view, shaft strongly compressed; atrium broad, with pair of short, slender processes extended dorsad from junction of shaft and atrium; shaft narrowed to obliquely truncate apex in lateral aspect, very slender in posterior aspect. Gonopore slit-like near basal 1/3 of shaft.  Distribution. Thailand (Prachuab) (Figure 27), Ethiopia.
Remarks. X. abyssinicus was described by Heller and Linnavuori [83] based on a male specimen from Ethiopia. This is the first record of the species from Asia. It is similar to X.  Distribution. Thailand (Prachuab) (Figure 27), Ethiopia.
Remarks. X. abyssinicus was described by Heller and Linnavuori [83] based on a male specimen from Ethiopia. This is the first record of the species from Asia. It is similar to X. nonattribus in the shape of aedeagus and styles but distinguished by the presence of a pair of basal processes at the junction of the aedeagal shaft and atrium. The aedeagal processes of the specimens from Thailand are longer than those illustrated for the holotype by Heller and Linnavuori [83] but other aspects of the male genitalia, including the strongly compressed aedeagal shaft and distinctively shaped style apex, are nearly identical, so we consider the observed variation to be intraspecific.
3.3.13. Xestocephalus cowboyocreus sp. nov. Figure 13J-L, Figure 18A-F, Figure 24N, and Figure 26E1 Male genitalia. Pygofer in lateral view higher than long, with many macrosetae on posterior margin, with posterodorsal process long, curved ventrad then recurved anteriorly; internal process dagger-like and directed ventrad. Valve short and rectangular. Subgenital plate extending posteriorly farther than pygofer apex, broad, linguiform, basal half horizontal and apical half vertical, with apices broadly rounded in lateral view, with multiseriate macrosetae and serially arranged lateral microsetae. Style S-shaped, apical dilation of apophysis scythe-shaped with apical 1/2 tapered strongly, outer margin dentate and provided with prominent spine. Connective cross-shaped, the side arms folded downward. Aedeagal shaft slender and tapering gradually to apex, subapex slightly curved anteriorly in lateral aspect, atrium shorter and broader than shaft in lateral view, with pair of short processes on middle projecting dorsad. Gonopore ventral, situated near midlength of shaft. Distribution. Thailand (Chiang Mai) ( Figure 27). Etymology. The species name is a combination of the English word "cowboy" and the Latin "ocreus" (leg), referring to the cowboy-boot-shaped style apex.
Remarks. The new species is similar to X. recipinams sp. nov. in the structure of the aedeagus but has the aedeagal processes shorter than 1/3 the length of the shaft, the pygofer process long and curved ventrad, and the style apex without a spine on the inner margin (aedeagal processes longer than 1/2 length of shaft, pygofer process curved dorsad and style with 2 or 3 large spines on inner margin in X. recipinams). Insects 2021, 12, x FOR PEER REVIEW 34 of 52   Male genitalia. Pygofer in lateral view higher than long, tapered to rounded caudal margin, many macrosetae on posterior half, with two distinct triangular dilations along ventroposterior margin; internal process of pygofer large hook-like and directed dorsad. Valve short and trapezoidal. Subgenital plate broad, linguiform, apex rounded, with two rows of macrosetae. Style S-shaped, apical dilation of apophysis with outer margin concave and provided with scattered teeth; inner margin with 2 or 3 large spines. Connective cross-shaped, the side arms folded downward. Aedeagus with basal apodeme shorter and broader than shaft, with pair of long processes arising near junction with shaft Male genitalia. Pygofer in lateral view higher than long, tapered to rounded caudal margin, many macrosetae on posterior half, with two distinct triangular dilations along ventroposterior margin; internal process of pygofer large hook-like and directed dorsad. Valve short and trapezoidal. Subgenital plate broad, linguiform, apex rounded, with two rows of macrosetae. Style S-shaped, apical dilation of apophysis with outer margin concave and provided with scattered teeth; inner margin with 2 or 3 large spines. Connective cross-shaped, the side arms folded downward. Aedeagus with basal apodeme shorter and broader than shaft, with pair of long processes arising near junction with shaft and extended posterodorsad, sinuate in posterior view; shaft slightly curved anteriorly, in lateral view with basal half uniform but apical half tapering to sharp apex. Gonopore ventral, situated near apical 1/3 of the shaft.   Distribution. Thailand (Nakhon Si, Petchaburi) ( Figure 27). Etymology. The species name is a Latin word, which refers to the unique appendages of the pygofer.
Remarks. The new species is similar to X. cowboyocreus sp. nov. in aedeagal structure but differs in having the aedeagal processes more than 1/2 the length of shaft, the pygofer process curved dorsad, and the style with 2 or 3 large spines on the inner margin (aedeagal processes less than 1/3 length of shaft, the pygofer process curved ventrad, and style without spine in X. cowboyocreus).
3.3.15. Xestocephalus limpidissimus sp. nov. Figure 19D-F, Figure 21A-F, Figure 24P, and Figure 26G1-G3. Description. Length: ♂2.8 mm, ♀3.2 mm. General color dark yellowish with dense cream-colored spots. Crown covered with several irregular pale markings between eyes. Vertex dark yellowish, cream-yellow around ocelli. Face cream-colored and immaculate. Pronotum dark yellowish mottled with even-distributed cream-colored spots. Scutellum mottled with two diverging dark patches at basal angles, apical area light, with a crescentlike marking. Forewings yellow and hyaline, with shadows along costal margin, apical portion, and veins. Ventral surface and legs uniform yellow.
Male genitalia. Pygofer in lateral view higher than long, with approximately 17 macrosetae on posterior half; internal processes small and triangular, directed ventrad. Valve short and trapezoidal. Subgenital plate broad, linguiform, apical portion rounded, lateral margins of apical 2/3 slightly curved inwards, with several macrosetae near middle and several rows of hairlike setae near inner margin. Style slender, S-shaped, subapical dilation of apophysis boot-shaped, only slightly curved, without teeth. Connective cross-shaped, the side arms folded downward. Aedeagus with dorsal apodeme slightly shorter than shaft, with a pair of sword-shaped processes on base, directed dorsally, and a short process on middle projecting dorsad; shaft moderately long, compressed, slightly curved anteriorly, tapering to sharply pointed apex in lateral view. Gonopore situated near midlength of shaft.
Female. Sternite VII posterior margin broadly concave with distinct median notch. Second valvulae ventral preapical angle obtuse. Third valvula dorsal margin with distinct notch in shallowly concave preapical section.
Material examined. Holotype  Distribution. Thailand (Lampang) (Figure 27). Etymology. The species name is a Latin word meaning lustrous and refers to the crown.

Remarks.
The new species is similar to X. japonicus Ishihara [32] in the shape of the aedeagus in ventral aspect but differs in having the aedeagal shaft thick, the dorsal apodeme with a short process on the middle, and a broader pair of basal processes (aedeagal shaft slender, dorsal apodeme without process on middle, and paired processes slender in X. japonicus). Insects 2021, 12, x FOR PEER REVIEW 38 of 52 Male genitalia. Pygofer relatively short, higher than long, posterodorsal margin with long process directed caudad, with several macrosetae, ventroposterior margin with moderately long process, arched dorsad; internal process large, hook-like and directed ventrad. Valve short and trapezoidal. Subgenital plate extending posteriorly farther than pygofer apex, broad, linguiform, basal half horizontal and apical half vertical, with apex  Male genitalia. Pygofer relatively short, higher than long, posterodorsal margin with long process directed caudad, with several macrosetae, ventroposterior margin with moderately long process, arched dorsad; internal process large, hook-like and directed ventrad. Valve short and trapezoidal. Subgenital plate extending posteriorly farther than pygofer apex, broad, linguiform, basal half horizontal and apical half vertical, with apex broadly rounded in lateral view, with multiseriate macrosetae and serially arranged lateral microsetae. Style S-shaped, apical dilation of apophysis scythe-shaped, outer margin dentate, with prominent rectangular spine preapically. Connective cross-shaped, the side arms folded downward. Aedeagus with basal apodeme shorter than shaft, shaft slender and slightly curved anteriorly, in lateral view tapered from base to bluntly rounded apex, with pair of basal processes extended along sides of shaft tapering apically. Gonopore ventral, situated near midlength of shaft, lower edge even with apex of processes. broadly rounded in lateral view, with multiseriate macrosetae and serially arranged lateral microsetae. Style S-shaped, apical dilation of apophysis scythe-shaped, outer margin dentate, with prominent rectangular spine preapically. Connective cross-shaped, the side arms folded downward. Aedeagus with basal apodeme shorter than shaft, shaft slender and slightly curved anteriorly, in lateral view tapered from base to bluntly rounded apex, with pair of basal processes extended along sides of shaft tapering apically. Gonopore ventral, situated near midlength of shaft, lower edge even with apex of processes.   Distribution. Thailand (Chiang Mai) ( Figure 27). Etymology. The species name alludes to the overall similarity of this species to X. biprocessus but the aedeagal processes are half as long as in the latter.
Remarks. The new species is similar to X. biprocessus Li and Zhang [35] but can be identified by the pygofer with a long process at the posterodorsal margin, the aedeagal shaft with basal processes less than 1/2 the length of the shaft, and the style apophysis with abprominent rectangular spine preapically (pygofer with short process at posterior margin, aedeagal shaft with basal processes more than 1/2 length of shaft, and style apophysis with triangular spine preapically in X. biprocessus).
Male genitalia. Pygofer in lateral view higher than long, with many macrosetae on posterior half, caudal margin dentate, with a short spine-like process on ventroposterior corner, directed caudad; internal processes triangular, directed ventrad. Valve short and rectangular. Subgenital plate extending posteriorly farther than pygofer apex, broad, linguiform, basal half horizontal and apical half vertical, with apex broadly rounded in lateral view, with multiseriate macrosetae and serially arranged lateral microsetae. Style Sshaped, apex of apophysis slender, scythe-shaped, outer margin dentate with incision, basal 2/3 of distal part with fish-scale pattern on surface, apical 1/3 narrower with striations. Connective cross-shaped, the side arms folded downward. Aedeagus with basal apodeme shorter than shaft, shaft straight and evenly tapered gradually to a point in lateral aspect, with pair of posterior basal processes parallel to shaft, broadened at apex and directed dorsad. Gonopore ventral near apical 1/3 of shaft.
Female. Sternite VII posterior margin slightly convex with distinct median notch. Second valvulae with ventral preapical angle obtuse. Third valvula with dorsal margin deeply concave preapically.
Distribution. Thailand (Petchaburi) (Figure 27). Etymology. The species name is a Latin word that refers to the hammer-like processes of the aedeagal shaft.
Remarks. The new species is similar to X. dimiprocessus sp. nov. but differs in lacking a long pygofer process and having the aedeagal shaft straight, with basal processes parallel to the shaft and broadened apically (pygofer with long process, aedeagal shaft slightly curved anteriorly, and basal processes tapered to apex in X. dimiprocessus). Insects 2021, 12, x FOR PEER REVIEW 41 of 52

Conclusions
Seventeen species of the leafhopper genus Xestocephalus Van Duzee from Thailand are reviewed based on a comparative morphological study, including twelve new species and four newly recorded species. As only one species of Xestocephalus was previously recorded from Thailand, our study increased the known fauna of this genus in Thailand by 94%. Two of the newly recorded species, described from elsewhere, were previously known to be from China and/or Japan, but two others were previously known to be only from Africa. This suggests that either these species are widespread in the Old World tropics or they have been accidentally introduced from Africa to Thailand (or vice versa). Further study is needed to elucidate the relationship between African and Southeast Asian populations of these species and to determine whether they also occur in other parts of the Old World tropics. At least one other species documented in our study, X. guttulatus, appears to be widespread in the Old World and some species belonging to other leafhopper genera (e.g., Exitianus Ball, Balclutha Kirkaldy, Cicadulina China) also have similarly broad distributions. This highlights the need for comprehensive global revisions of such large, widespread genera and the importance of reviewing the taxonomic literature from more than one region when attempting to identify specimens from previously understudied regional faunas.
As in the other large genera of Cicadellidae, less than half of the species of Xestocephalus are known only from a few or single localities ( Figure 27). Consistent with general worldwide observation, most of the species documented in our study are, so far, only known to be from Thailand. Most of these apparent endemics are recorded from a few or single localities. Nevertheless, four of the new species described from Thailand appear to be more widespread within the country, and, therefore, it seems likely that they will eventually be found in the neighboring parts of Southeast Asia. Further sampling and comparative morphological studies are needed to elucidate the phylogenetic and biogeographic patterns in this large, diverse, and globally distributed genus of leafhoppers.