Female. Body length 14.2 mm, forewing length 10.3 mm.

Colour. Body black with following parts yellow: A1–A4; base of A5; band immediately after apical margin of clypeus; base of mandible; maxillary and labial palps; tegula; pronotal collar; pronotal lobe; fore coxa; base of mid- and hind-coxae; fore- and mid-trochanters ventrally, femora, tibiae, and tarsi; half of base of hind tibia; lateral sides of petiole, broad base of G2 and G3; apical bands of G1–G5. Following parts ferruginous: apical margin of clypeus; apical two-thirds of mandible; two-thirds of apex of A5, A6–A12; hind trochanter, femur, half apex of tibia and tarsi; half base of petiole dorsally; sides and ventral surface of G6. Veins of wings yellow to brown.

Vestiture. Golden on head and mesosoma, white on metasoma.

Head (Fig. 1A, B). In anterior view, nearly round, width about 1.2× height, its sides roundly convergent below; apex of clypeus blade-shaped, round apically; mandible without tooth; SAT moderately raised with short median carina; ASR moderately high with three distinct carinae; PAF shallow, flat-bottomed; ocelli round and distinctly protruded; frons with rather narrow furrow medially and small punctures, sparse on median area and dense on lateral sides; vertex depressed below level of upper eye margin, with small sparse punctures; occipital carina complete; relative lengths of A1: A2: A3: A4: A5 = 27: 14: 48: 28: 28, respectively; relative lengths of minimum interocular distance at the vertex: Ocellocular distance (distance between inner margin of eye and outer margin of hind ocellus): Ocellar diameter: Postocellar distance (distance between inner margins of hind ocelli) = 37: 3: 12: 7, respectively; ratio of minimum interocular distance at the vertex: minimum interocular distance at base of clypeus = 1.

Mesosoma (Fig. 1C-F, Fig. 2A). Pronotal collar with anterior part moderately swollen posteromedially, posterior part discoloured; pronotal lamella triangularly protruded, with apical angle approximately 150°; subalar area of mesopleuron with pent-roofed structure distinctly developed; mesoscutum, scutellum, metanotum, propodeum with sparse, fine, small punctures; mesopleuron with rather dense punctures; propodeum without lateral carina, with median groove dorsally, shallow on basal half and deep on apical half, posterior surface with a series of horizontal striae and median grooves conspicuously deep; gastral socket rim simple, nearly roundly elevated. Wings hyaline; forewing with stigma as long as prestigma.

Metasoma (Fig. 2B-D). Shiny, with very sparse micropunctures on petiole and G2–G5; petiole flask-shaped, length about 4× its apical width and about 1.3× that of G2 and G3 combined, with its apex more highly protruding than base of G2; tergum of G6 rounded apically, rugose basally, impunctate, its apex slightly curved upwards.

Male. Body length 12.6 mm, forewing length 9.1 mm.

Structures as in female, but differing as follows:

Colour. A1–A7 yellow; A8–A13, half apex of clypeus, maxillary and labial palps ferruginous, half apex of mandible black.

Head (Fig. 3A-C). A3 shorter than A1 and A2 combined, but longer than A4, A5; relative length of A1: A2: A3: A4: A5 = 19: 9: 20: 15: 15; A13 as long as A9–A12 combined; relative length of minimum interocular distance at the vertex: Ocellocular distance: Ocellar diameter: Postocellar distance = 32: 5: 8: 6, respectively.

Metasoma (Fig. 4A-C). Petiole with length 3.5× its apical width.

Genitalia (Fig. 4D-F). Brownish-yellow, except apical part of sickle black. Penis valve with shoulder, sickle and apical part; shoulder horizontal; sickle conspicuously curved, with its apex distinctly pointed; apical part moderately curved; paramere with two lobes at apex (namely, ventral and dorsal lobes), their length about equal, ventral lobe much broader than dorsal lobe; furrow between two lobes deep, reaching apex of inner expansion of basiparamere; inner margin of ventral lobe and inner margin of outer area of basiparamere in a line moderately curved medially. Dorsal lobe with some long, erect setae apically; ventral lobe with 5–6 long, erect setae at apex, subapical part with several sparse, erect setae along outer margin.

The new species runs close to T. shakha Tsuneki, 1979 in a key ofTrypoxylon of the Indian subcontinent and Southeast Asia (Tsuneki 1979). In T. shakha and in the newly-described species, the females display the following characters: vertex depressed below level of upper eye margin; PAF flat-bottomed; occipital carina complete; propodeum without lateral carinae, dorsal area with furrow; frons, mesoscutum, scutellum, metanotum and propodeum with small sparse punctures. Following parts with yellow integument: A1–A4, pronotal collar, fore- and mid-legs, except broad base of mid-coxa, tergal base of G2–G4, apical bands of G3–G5. Vestiture golden on head and mesosoma. Females of the new species differ from those of T. shakha as follows: Clypeus round apically (in T. shakha, clypeus not round apically, with median margin highly protruded and truncated apically); PAF shallow (in T. shakha, PAF deep); SAT dorsally with medial carina short, not enlarged, not broadly excavated (in T. shakha, SAT dorsally with median carina enlarged into a smooth and round area and broadly excavated); ASR moderately raised (in T. shakha, ASR highly raised, bicarinate on apex); vestiture white on metasoma (in T. shakha, vestiture golden on metasoma).

The specific name of this new species refers to the sickle shape of the penis valve.

Vietnam: Vinh Phuc Province.