Ennearthron acuticornum sp. nov.

Figs. 1 (A–E), 2(A–F), 7

Chinese vernacular name: 尖RM刻Ìdzę

Type material. Holotype: CHINA: male, “ China: Yunnan, Puer (üDz), Jingdong Yi Autonomous County (Ŗ 东 ḆNJÞà县), Wuliang Mountain (ĿDZƜ), 24°20’58’’N, 100°42’05’’E, 1970 m, 14.XI.2020, leg. Da-Rui Mo ”.

Paratypes: CHINA: 4 males, 4 females, same data as the holotype.

Diagnosis: The new species E. acuticornum sp. nov. differs from all the known species by body size (all the known species are less than 2.00 mm, the E. acuticornum sp. nov. more than 2.00 mm).

In addition to this, it differs from all described species of the genus by the pronotal horns shape of male (E. acuticornum sp. nov. with slender and acuity pronotal horns; E. robusticorne strongly produced forward into two subtriangular large projections which protrude beyond the apex of the head and are somewhat broadly rounded at apices; the remaining nine species more or less produced to form a pair of triangular slightly small plates). The new species differs from E ishiharai by antennae (E. acuticornum sp. nov. with slightly longer than broad segment 3 and segment 4 about one-half as long as segment 3; E. ishiharai with rather thickened segment 3 but 4th only slightly shorter than 3rd). It is also easily distinguished from E. cornutum and E. victori by the presence of an abdominal sex patch in the male.

Description. Male. Fully pigmented adult. Measurements in mm: TL 2.29, PL 0.73, PW 0.97, EL 1.55, EW 1.13, GD 0.84. Ratios: PL/PW 0.75, EL/EW 1.37, EL/PL 2.12, GD/EW 0.74, TL/EW 2.03.

Body (Fig. 1B) elongate, convex, yellowish brown to dark brown; dorsal with thick and long setae, ventral with slender setae.

Head wider slightly than long, with sparse punctures and setae, anterocephalic edge strongly elevated forming a pair of broad-based, subtriangular plates, narrowly separated by a small distinct notch. Compound eyes finely facetted and large, each bearing approximately 90 ommatidia; GW 0.10 mm. Antennae (Fig. 2D) bearing nine antennomeres with the following lengths (in mm, right antenna measured of a female paratype): 0.09, 0.06, 0.07, 0.03, 0.02, 0.02, 0.08, 0.09, 0.12. Mandibles are asymmetrical, with well-developed, transversely ridged molae.

Pronotum (Fig. 1B) is slightly raised in the middle with shallow and fine punctures bearing thick and long setae (~ 0.02 mm), the surface between punctures smooth; anterior angles produced forward, rounded; posterior angles rounded; anterior edge strongly produced forward and deeply emarginate medially forming a pair of slender and acuity horns (the largest spacing of horns about 0.38mm); lateral edge (Fig. 1E, arrow) usually narrow, weakly crenulate (best seen in ventral view), barely visible from above; posterior edge curvature.

Scutellar shield developed, with a few punctures and setae; subtriangular, rounded at apex; BW 0.13 mm.

Elytra (Fig. 1B) 1.4 times as long as broad, 2.0 times as long as pronotum, punctures coarse; setae thick and long (~ 0.03 mm); sides subparallel in basal two-thirds, then gradually convergent to the apex.

Protibia with outer apical angle produced to form a tooth; pro, meso and metatibiae tibia with similar shape and length, slightly expanded.

Prosternum (Fig. 1A) in front of coxae slightly convex; prosternal process subparallel-sided and somewhat broadened near apex, higher than the procoxae (best seen in lateral view).

Metaventrite (Fig. 1A) is slightly emarginate in the middle, with sparse punctuation and bristles; discrimen with nearly two-thirds the length of ventrite. Abdominal ventrites (Fig. 1A) with fine setae and shallow punctures, the surface between them microreticulate; the first abdominal ventrite 2.1 times as long as 2nd, the ventrites bearing a circular, setose and margined sex patch in the middle, with a transverse diameter of 0.05 mm; length of the ventrites (in mm) as follows: 0.30, 0.14, 0.13, 0.12, 0.12.

Aedeagus 2.2 times as long as ventrite 5. Tegmen (Fig. 1D) 2.2 times as long as wide, widest at apical eighth; widen gradually from base to apex; sides gradually diverging to apical fourth, where on each side there is a slender apically directed lobe, apex broadly rounded. Penis (Fig. 1D) is as long as tegmen, 5.6 times as long as wide, with a subacute apex and moderately long, sides parallel from basal to middle.

Female (Fig. 2). Similar to male, except for the following points: anterocephalic edge without strongly subtriangular plates, but with an arcuate lamella on each side; pronotum with anterior edge broadly rounded, without horns; first abdominal ventrite without a sex patch. Ovipositor (Fig. 2F) 4.0 times as long as wide, widest at the base; paraprocts (Fig. 2F) 1.15 times as long as gonocoxites, longitudinally oriented; gonocoxites 1.8 times as long as their combined widths, each slightly narrowed basally then middle to form a subcylindrical extension, beyond middle gradually narrowed rounded at apex. each gonostylus 0.15 times as long as respective gonocoxite, 4.01 times as long as wide.

Measurements. Males (n = 4, including the holotype; mm): TL 2.02–2.31 (2.21 ± 0.13); PL 0.55–0.73 (0.67 ± 0.08); PW 0.73–0.97 (0.87 ± 0.11); EL 1.47–1.61 (1.53 ± 0.06); EW 0.90–1.13 (1.03 ± 0.09); GD 0.73–0.95 (0.86 ± 0.10). PL/PW 0.74–0.84 (0.77 ± 0.05); EL/EW 1.36–1.63 (1.49 ± 0.11); EL/PL 2.12–2.68 (2.31 ± 0.26); GD/EW 0.80–0.86 (0.83 ± 0.03); TL/EW 2.03–2.23 (2.14 ± 0.09).

Females (n = 4; mm): TL 1.98–2.26 (2.13 ± 0.11); PL 0.55–0.72 (0.65 ± 0.07); PW 0.76–0.89 (0.85 ± 0.06); EL 1.40–1.61 (1.49 ± 0.09); EW 0.96–1.10 (1.08 ± 0.10); GD 0.82–0.88 (0.85 ± 0.02).

PL/PW 0.72–0.82 (0.77 ± 0.04); EL/EW 1.17–1.49 (1.39 ± 0.15); EL/PL 1.94–2.62 (2.32 ± 0.30); GD/EW 0.68–0.91 (0.80 ± 0.10); TL/EW 1.84–2.42 (2.09 ± 0.24).

Distribution. Wuliang Mountain, Yunnan, China (Fig. 7).

Host fungi. Unidentified Polyporaceae.

Etymology. The specific name ‘acuticornum’ refers to the pronotal horns being slender and acuity.