Mesonemoura trapezoidea, Li, Weihai, Cui, Jianxin & Yang, Ding, 2017

Li, Weihai, Cui, Jianxin & Yang, Ding, 2017, Three new species of Mesonemoura (Plecoptera: Nemouridae) from China, Zootaxa 4272 (2), pp. 276-284 : 278-280

Mesonemoura trapezoidea sp. nov.

( Fig. 2 )

Diagnosis. This species is characterized by the tergum IX being produced into a wide, symmetrical, trapezoidal mid-posterior protuberances ca. as 8X wide as length ( Fig. 2 a) and by the flagellum of the epiproct being long and strongly left-curved medially, with a fan-like extension flanked by an enlarged bifurcate apex ( Figs. 2 d, 2f).

Adult. Male forewing length ca. 10.2 mm. Head and appendages brown. Thorax dark brown; legs brown but basal half of femora pale brown; wing membranes subhyaline, veins brown. Abdominal segments brown, terminalia darker; hairs on abdomen mostly pale.

Male terminalia. Tergum IX sclerotized, with a wide, symmetric trapezoidal mid-posterior protuberances ca. as 8X wide as length, covered with ca. 12 short triangular, black spines along the nearly truncate posterior margin, posterolateral corners slightly enlarged and in lateral aspect apex enlarged and truncate ( Figs. 2 a & 2c). Sternum IX with hypoproct wide and trapezoidal at basal half, then distinctly tapering medially toward nipple-shaped tip, vesicle generally claviform, basal stalk and apex constricted, ventral surface most membranous ( Fig. 2 b). Tergum X sclerotized, with a narrow median longitudinal slit in the usual concavity below epiproct, each anterolateral margin bearing ca. 10 tiny spines ( Fig. 2 a). Cercus one-segmented with an apical remnant of second segment, slightly sclerotized and apex moderately tapering, longer than wide ( Figs. 2 a–2c). Epiproct has strongly sclerotized entire transverse sclerite divergent in two thin lateral bands that end subapically, subapical portion distinctly enlarged that renders the apex elliptical, and after KOH clearing, present a distinct bowtie-shaped sclerite; apex bearing a long, strongly left-curved flagellum, being wide and mostly parallel-sided except fan-shaped median extension flanked by an enlarged bifurcate apex, the curve being slightly at basal half and distinctly turning left medially nearly forming a right angle ( Figs. 2 c, 2d & 2f). Paraprocts divided into three lobes: outer lobe strongly sclerotized forming a dark lateral band, apical portion fused with the tip of median lobe; median lobe broad at base with rectangular membranous area adjacent to inner lobe, apex produced in a sclerotized tube-like structure; inner lobe is a small sclerotized triangle ( Fig. 2 e).

Female. Unknown.

Type Material. Holotype: male ( HIST), China: Guizhou Province, Zunyi, Xishui County, Sancha River , 2012. III. 30, W.H. Li & W.F. Shi.

Distribution. China (Guizhou Province).

Etymology. The epithet refers to the trapezoidal mid-posterior protuberances of tergum IX.

Remarks. The new species is similar to M. sbordonii Fochetti and Sezzi, 2000 and M. yulongana Li & Yang, 2009 both described from Yunnan Province of southwestern China, in the general shape of the epiproct, and shares similar shaped paraprocts with M. dilatata Du & Ji 2015 from Tibet. Males of M. trapezoidea may be easily separated from these species by the presence of symmetrical, trapezoidal, mid-posterior protuberances of tergum IX. In M. sbordonii and M. dilatata , tergum IX is not produced medially and tergum IX of M. yulongana has short asymmetrical mid-posterior protuberances.

Figures

FIGURE 2. Mesonemoura trapezoidea sp. n. male. a. Terminalia, dorsal view; b. Terminalia, ventral view; c. Terminalia, lateral view; d. Epiproct, dorsal view. e. Paraproct, caudal view; f. Apex of epiproct flagellum, oblique anterolateral view.