Eurystylus yasunagai Kim & Jung, 2025

Kim, Junggon, Keetapithchayakul, Tosaphol Saetung, Phan, Quoc Toan & Jung, Sunghoon, 2025, Taxonomic review of the genus Eurystylus Stål (Hemiptera: Miridae: Mirinae) from Vietnam, including a new species description, Zootaxa 5679 (2), pp. 268-276 : 269-270

Eurystylus yasunagai Kim & Jung sp. nov.

( Figs 1A–E , 2A–D )

Diagnosis. Recognized by the almost fuscous or blackish brown dorsum; pronotum entirely blackish brown; propleuron mostly blackish brown, anterior part with creamy yellows band; posterior part of mesepisternum creamy yellow, plate dorsal to mesepisternum entirely creamy yellow, forming a continuous yellowish band; mesepimeron and metepimeron entirely blackish brown ( Fig. 1E ); scutellum almost blackish brown with indistinct pale marking apically; hemelytra entirely blackish brown; hypophysis of left paramere broad and rounded; right paramere slightly curved; endosoma membranous with three sclerites ( Fig. 2A–D ).

Description. MALE: Coloration: unicolorous, mostly fuscous or blackish brown. Head: mostly fuscous with brownish spots near compound eye; antennae mostly fuscous; first segment entirely fuscous; second, third and fourth segments mostly fuscous except for pale base; labium mostly fuscous except for brownish third labial segment. Thorax: pronotum entirely fuscous; propleuron mostly fuscous, with creamy yellow band along anterior margin; mesepisternum partly creamy yellow and fuscous, posterior part creamy yellow, above plate entirely creamy yellow; mesepimeron and metepimeron entirely fuscous; scent efferent system mostly creamy yellow; scutellum mostly entirely or mostly fuscous except for indistinct pale apex; hemelytra entirely fuscous; legs mostly fuscous; middle tibiae with pale marking medially; hind tibiae with pale ring medially. Abdomen: partly brown and fuscous. Surface and vestiture: body weakly glossy, minutely and vaguely punctured, covered with golden or silver tuft of hair. Structure: body elongated, length 5.11–5.23. Head: prognathous, width longer than length; vertex wider than single compound eye width; antennae shorter than body length; first segment flattened, longer than head width, as long as 0.6 times second segment; second segment clavate, longer than combined third and fourth segment; third and fourth segments linear, third segment longer than fourth segment; proportion of first to fourth antennal segments 1.15: 2.05: 0.83: 0.57; labium reaching middle coxae. Thorax: pronotum hexagonal, longitudinal length as long as 0.65 times basal maximal width, posterior margin sinuate; calli weakly swollen; pronotal collar stout, broad, diameter subequal to maximum diameter of first antennal segment; scutellum flat, anterior width shorter than length, as long as 0.68 pronotal maximal width, longitudinal length longer than commissure length; lateral margin of hemelytra almost straight; cuneus small. Abdomen: rounded, reaching to apex of cuneus. Genitalia: left paramere C-shaped, hypophysis broad and rounded, apex sharp, sensory lobe narrow; right paramere slightly curved, hypophysis hook-shaped; endosoma membranous with three sclerites; primary lobal sclerite (pl) straight, its apex enlarged and blunt; median lobal sclerite (ml) long, tapered to apex; third lobal sclerite (tl) short, tapered to apex ( Fig. 2A–E ). FEMALE: Coloration: as in male except for second antennal segment brown and dark brown with small pale spot in dorsal side. Surface and vestiture: as in male. Structure: as in male, except for body length, 5.48 and proportion of antennal segments: 1.25: 2.04: 0.78: 0.57.

Measurements (in mm). Male (n=4)/Female (n=1) Body length, clypeus–apex of membrane: 5.11–5.23/5.48; head length, excluding collar: 0.79–0.81/0.82; head width, including compound eyes: 1.08–1.10/1.12; vertex width: 0.44–0.45/0.45; 1 st antennal segment length: 1.15–1.18/1.25; 2 nd antennal segment length: 2.05–2.09/2.04; 3 rd antennal segment length: 0.83–0.84/0.78; 4 th antennal segment length: 0.57–0.58/0.57; total antennal length: 4.60– 0.69/4.63; mesial pronotal length: 1.30–1.32/1.24; posterior pronotal maximal width (straight): 1.97–1.98/1.97; anterior scutellar width: 1.32–1.34/1.34; mesial scutellar length: 1.28–1.30/1.34; commissure length: 1.11–1.14/1.05; maximal width across hemelytron: 1.09–1.10/1.18

Biology. This species was collected from the flowers of broad-leaved trees.

Distribution. Vietnam (Southern).

Etymology. The species is named in honor of Dr. Tomohide Yasunaga, a prominent specialist in the taxonomy of Miridae , in recognition of his extensive contributions to the family, particularly in the Oriental Region including studies on the genus Eurystylus . The name is a noun in the genitive case.

Material examined. [ ZCDTU] Holotype: 1♂, Loc Tan (11.6463°N, 107.7036°E, 880 m altitude), Bao Lam District, Lam Dong Province, Vietnam, 30.iv.2025, J. Kim leg. ( DTUHMM0060 ) ; [ ZCDTU] Paratypes: 3♂♂ 1♀, same data as holotype ( DTUHHM0061-0064 ) .

Discussion. The new species differs from most congeners by the unicolorous fuscous dorsum. Eurystylus yasunagai sp. nov. is distinguished from the most similar congener from Taiwan, E. jingfui Yasunaga et al. 2017 by entirely fuscous posterior margin of propleuron (vs. posterior margin with white band); posterior part of mesepisternum creamy yellow (vs. mesepisternum entirely fuscous); plate dorsal to mesepisternum entirely creamy yellow (vs. mostly fuscous with yellowish margin); metepimeron entirely fuscous (vs. posterior part metepimeron white); and endosoma with three sclerites (vs. endosoma with one long and apically sharp sclerite).

Meanwhile, in the original description of E. jingfui, Yasunaga et al. (2017) mentioned a population from Thailand and Southeast Asia that resembles E. jingfui but have white longitudinal striae on the lateral sides. Considering both external morphology and distribution, this population is most likely our new species, E. yasunagai sp. nov.

Figures

FIGURE 1. Habitus of Eurystylus spp. A–E: Eurystylus yasunagai sp. nov.; F: E. burmanicus; G: E. coelestialium; H: E. ryukyus; I: E. sauteri; A: Holotype male in dorsal view; B: ditto, in lateral view; C: Paratype female in dorsal view; D: ditto, in ventral view; E: thorax in lateral view. Scale bar: 1 mm.

FIGURE 2. Male genitalia of Eurystylus spp. A–E: Eurystylus yasunagai sp. nov.; F–H: E. ryukyus; I–L: E. sauteri; A, F, I: left paramere; B–C, G, J: right paramere; D–E, H, K, L: endosoma; bt: basal sclerotized teeth; fl: fourth lobal sclerite; ml: median lobal sclerite; ph: phallotheca; pl: primary lobal sclerite; tl: third lobal sclerite. Scale bar: 0.2 mm.