Euxiphocerus Parent, 1935: 122. Type species: Euxiphocerus wulfi Parent, 1935 (monotypy).

Occiput is weakly convex backward. Compound eyes have tiny setulae between facets. Male Compound eyes are narrowly separated on face. Male face is narrow, narrowing downward. Vertex is not excavated. Upper occiput is distinctly concave. Vertical seta is nearly at level of oculus. Postocular setae are one-rowed and flattened. Male antennal pedicel is greatly reduced. Male postpedicel is 5–6 times longer than high at base. Arista-like stylus is apical. Mesonotum has flat mid-posterior slope. Posterior pair of acrostichal setae are distinctly larger than preceding pairs and offset laterally. 6 strong dorsocentral setae are decreasing in size anteriorly. Proepisternum is not haired, only with separate setae on mid-lower portion. Setulae on legs are uniformly short. Hind coxa has 1 outer seta at middle. Mid and hind femora do not have anterior preapical setae. R₄₊₅ and M₁ are subapically bowed. Distal sector of R₄₊₅ and M₁ have flexion. Anterior cubital cell is absent. Cua+CuP vein is weak. Male abdominal segment 6 is large triangular-shaped, with setae and setulae. Male 7th abdominal segment is short and has distinct tergite and sternite. Male genitalia are mostly exposed. Male hypopygium is sessile, with a pair of large and a pair of small epandrial lobes, with broad and deeply divided dorsal and ventral arms of surstylus. Apical subepandrial processes are absent and postgonite is indistinct. Male cercus usually thickened basally (based on Grichanov 2009).

Male (Figs 3, 4, 5). Body length: 2.6–2.8 mm. Wing length: 2.3–2.4 mm.

Figure 3.  

Euxiphocerus lignicola sp. nov.; A male, lateral view; B female, lateral view; C male wing; D male antenna, lateral view. Scale bars: 0.5 mm.

Figure 4.  

Euxiphocerus lignicola sp. nov.; A male abdomen, lateral view. Scale bar: 0.1 mm. Abbreviations: epd = epandrium; st = sternite; tg = tergite.

Figure 5.  

Euxiphocerus lignicola sp. nov.; A male genitalia, lateral view; B male genitalia, ventral view. Scale bars: 0.05 mm. Abbreviations: d sur = dorsal surstylus; epd = epandrium; epd l = epandrial lobe; hyp = hypandrium; phal = phallus; v sur = ventral surstylus.

Head: metallic bluish green with mainly black setae and covered with white tomentum; one long ocellar seta reclinate and divergent; one short postocellar seta proclinate; one long vertical seta proclinate and convergent, and positioned slightly forward than ocellar seta line; one pale yellow postvertical seta convergent and proclinate; postocular setae pale yellow in a single row; face and clypeus covered with thick white tomentum; compound eye with tiny white setulae between facets; lower occiput with one long pale yellow seta and several pale yellow setulae; scape dark brown to pale brown without setae; pedicel pale brown with apical ring of setae; postpedicel mostly dark brown, pubescent and long, six times as long as basal width, and basal 1/5 swollen and ventrally pale orange; arista-like stylus brown, short pubescent, and slightly shorter than postpedicel; palpus pale yellow with pale yellow setulae; proboscis brown with pale setulae. Thorax: metallic bluish green with mainly dark brown setae and covered with white tomentum; 11–12 pale brown acrostichial setae biseriate; six dorsocentral setae; one long and two tiny postpronotal setae; one presutural and one postsutural intra-alar setae; one presutural and two postsutural supra-alar setae; two notopleural setae; one postalar seta; two marginal scutellar setae, dark brown median seta about twice as long as pale brown lateral seta; proepisternum with one long and 2–3 fine pale yellow setae. Legs: mainly pale yellow and covered with pale yellow setulae; fore coxa with white setae and setulae; fore femur without strong setae; fore tibia with one short brown posterodorsal seta; fore tarsus without strong setae; fore tarsomere 5 slightly brownish at apical half; relative ratio of fore femur, tibia and tarsomere 1–5: 8.8:9.0:3.3:1.3:1.0:0.8:1.0; mid coxa with brown basal half with white setae and setulae; mid femur without strong setae; mid tibia with one anterodorsal and two posterodorsal setae and apical ring of dark brown setae; mid tarsus without strong setae; mid tarsomere 5 slightly brownish at apical half; relative ratio of mid femur, tibia, tarsomere 1–5: 10.8:11.3:5.8:3.5:2.3:1.3:1.0; hind coxa with one white seta; hind femur without strong setae; hind tibia with one anterodorsal and five posterodorsal setae and apical ring of dark brown setae; hind tarsus without strong setae; hind tarsomere 5 slightly brownish at apical half; relative ratio of hind femur, tibia, tarsomere 1–5: 8.2:9.6:1.6:4.2:2.2:1.6:1.0. Wings: hyaline; veins mainly pale brown; C ended at M₁; Sc fused to R₁ at 1/3; R₁ slightly curved to posterior; R₂₊₃ almost straight; R₄₊₅ slightly curved to posterior; M₁ straight and slightly curved to anterior at 3/4; R₄₊₅ and M₁ slightly convergent at apex; M₄ straight; crossvein dm-m straight; relative ratio of apical M₄ to dm-m: 1.0:0.6; CuA+CuP fold-like and not reaching the wing margin; calypter pale yellow with pale yellow setulae on fringe; halter pale yellow. Abdomen: metallic bluish green with mainly pale yellow to pale brown setae and setulae and covered with white tomentum; posterior margin of tergites with relatively long setae; 7th tergite short, covered by 6th segment; epandrium dark brown, longer than wide with inner dense setulae between the surstylus and epandrial lobe; hypandrium fused to epandrium, simple; epandrial lobe broad, with dense setae at inner side; surstylus pale yellow and deeply bifurcated, dorsal lobe finger-like, ventral lobe almost same length as dorsal lobe with thick setae at inner side; cercus pale yellow and slender, basal 2/5 thick; phallus apically pointed.

Female (Figs 3, 6). Body length: 2.7–3.1 mm. Wing length: 2.4–2.7 mm. Almost the same as the male, except for some characteristics: postpedicel short, slightly longer than width; arista-like stylus about 2.5 times longer than postpedicel; palpus and proboscis larger than those in male; anterior half of tergite 8 dorsally spilited; tergite 10 with anterior one pair and a row of posterior 3–4 pairs of acanthophorite spines; cercus digitiform and arosed to upside with one ventral setula.

Figure 6.  

Euxiphocerus lignicola sp. nov.; A female genitalia, lateral view. B ditto, dorsal view. Scale bars: 0.1 mm. Abbreviations: acanth sp = acanthophorite spine; cer = cercus; st = sternite; tg = tergite.

Setae on head and thorax are mainly black and dark brown. Arista-like stylus without any ornament at apex. Fore and hind coxae are mainly yellow to pale yellow. All coxae have white setae. Setae on abdomen are mainly pale yellow to pale brown. Dorsal lobe of surstylus without ventral projection.

The specific name is derived from the Latin words "lignum," meaning "wood" or "timber," and "cola" meaning "inhabitant" or "dweller."

Species of the genus Systenus are known to be tree-trunk associated, and the larvae develop in tree-hole debris (Oboňa et al. 2012, Vaillant 1978). In this research, this new species was also observed on tree trunks and in tree holes inhabited by other Systenus spp. In this regard, Euxiphocerus and Systenus species are believed to have similar or the same ecologies.

This new species resembled Euxiphocerus savannensis capensis Grichanov, 2009, but it can be differentiated by the following characteristics: coxae with white setae (vs. with black setae); abdomen with pale yellow setae (vs. with black setae); dorsal lobe of surstylus without ventral projection (vs. with ventral projection).

This is the first record of the genus Euxiphocerus from the PA.

Systenus jinxiuensis Lin & Yang, 2022: 294 (Type-locality: China, Guangxi, Jinxiu).

This species has some similar morphological features of genus Euxiphocerus: elongated postpedicel (6 times longer than width), a pair of large and a pair of small epandrial lobes, and a deeply bifurcated surstylus in males.

Systenus sinensis Yang & Gaimari, 2004: 176 (Type-locality: China, Yunnan, Xishuangbanna).

This species has some similar morphological features of genus Euxiphocerus: elongated postpedicel (4.8 times longer than width), a pair of large and a pair of small epandrial lobes, and a deeply bifurcated surstylus in males.