KEY TO THE SPECIES OF TRYPOXYLON FROM NORTHERN VIETNAM 1. Frons with shield (Figs 7, 10, 13); gaster wholly black (Figs 19, 26, 28) .......................................................... 2 — Frons without shield (Figs 1, 3, 5–6, 8–9, 11–12, 14–16); gaster wholly or partly ferruginous (Figs 17–18, 20–25, 27, 29–30) .................................................................... 4 2. Frontal shield with upper lateral carinae broadly interrupted, dorsal carina distinctly present, lower carina straight (Fig. 7); pronotum undiscoloured posteriorly; body length 12–13 mm (female) ......... T. interruptum Tsuneki, 1978 — Frontal shield with upper lateral carinae uninterrupted, lower carina curved or lightly zigzag (Figs 10, 13); pronotum discoloured or undiscoloured posteriorly; body length 8–12 mm ............................................................ 3 3. Frontal shield with lower area nearly flat, upper area deeply depressed around fore ocellus (Fig. 10); interantennal transverse carina without hole above (Fig. 10); mesoscutum weakly microcoriaceous; body length 8 mm (female) .............................. T. pileatum F. Smith, 1856 — Frontal shield with lower area conspicuously inclined (Fig. 13); interantennal transverse carina with deep hole above (Fig. 13); mesoscutum fairly and sparsely punctate; body length 11–12 mm (female) .................................... ............................................ T. thaianum Tsuneki, 1961 4. Gaster black with median area (from apex of petiole to gastral segment 3 or from apex of petiole to base of gastral segment 4) ferruginous (Figs 17, 20, 22–23) ............. 5 — Gaster wholly or from apex of petiole to last gastral segment ferruginous (Figs 18, 21, 24, 25, 27, 29–30). ............. 8 5. Clypeus conspicuously protruded mediapically (Fig. 8); gaster from apex of petiole to gastral segment 3 ferruginous lateraldorsally, darkly marked dorsally and ventrally (Fig. 20); legs black (Fig. 20); IODs = 1:1 (Fig. 8); body length 11–14 mm (both female and male) ..................... ........................................... T. orientale Cameron, 1904 — Clypeus round mediapically (Figs 1, 3, 11); gaster from apex of petiole to base of gastral segment 4 ferruginous (Figs 17, 22–23); legs black, with ferruginous spots (Figs 17, 22–23); IODs varied (Figs 1, 3, 11) ..................... 6 6. SAT with apical margin roundly curved and acutely edged, produced over PAFs; head lightly convergent at lower part (nearly round); IODs = 3:2 (Fig. 11); flagellum black (Figs 11, 23); body length 12–13 mm (female) ... ........................................... T. prominens Tsuneki, 1979 — SAT without apical margin roundly curved and acutely edged; head conspicuously convergent at lower part; IODs = 5:4 or 4:3 (Figs 1, 3); flagellum brown beneath (Figs 17, 22); body length 10–19 mm ......................... 7 7. Vertex conspicuously depressed (Fig. 1); anterior margin of clypeus moderately curved (Fig. 1); IODs = 5:4 (Fig. 1); in males, flagellomere 11 in lateral view distinctly tapering (Fig. 2); body length 14–19 mm (both female and male) ...................................... T. bicolor F. Smith, 1856 — Vertex undepressed (Fig. 3); anterior margin of clypeus conspicuously curved (Fig. 3); IODs = 4:3 (Fig. 1); in males, flagellomere 11 in lateral view not tapering, lightly curved medially; body length 9–14 mm (both female and male) ................................ T. petiolatum F. Smith, 1858 8. Gaster wholly ferruginous (Fig. 27); scape, pedicel and base of flagellomere 1 yellowish brown (Fig. 12); body length 11–12 mm (female). T. rufigaster Tsuneki, 1979 — Gaster from apex of petiole to last gastral segment ferruginous (Figs 18, 21, 24–25, 29–30); scape, pedicel and base of flagellomere 1 black or ferruginous (Figs 5–6, 9, 14–16) .......................................................................... 9 9. PAF shallow (Fig. 9); IODs = 10:9 (Fig. 9); legs mostly black (Fig. 21); body length 17 mm (female) ................ ................................... T. paeninsulicola Tsuneki, 1979 — PAF deep (Figs 5–6, 14–16); IODs varied; legs mostly ferruginous or pale brown (Figs 18, 24–25, 29–30) .. 10 10. IODs = 3:1 (Fig. 14); clypeus distinctly pointed mediapically (Fig. 14); scape and pedicel pale brownish (Fig. 14); body length 9 mm (female) ........ T. tomi Tsuneki, 1979 — IODs varied; clypeus nearly round or largely truncated mediapically; scape and pedicel ferruginous or black ... .................................................................................... 11 11. Anterior oblique flattened area of SAT with distinct hole (Fig. 16); gastral segment 5 and 6 darkly red (Fig. 30); IODs = 5:4 (Fig. 16); body length 10 mm (male) ......... ................................................... T. yumi Tsuneki, 1979 — Anterior oblique flattened area of SAT without hole; gastral segment 5 and 6 ferruginous (Figs 18, 24–25); IODs = 3:2 or 10:9 (Figs 5–6, 15) ............................ 12 12. Antennae wholly and legs mostly ferruginous (Fig. 24); ASR roundly inclined to PAF; hairs whitish brassy; body length 13 mm (female) .... T. varipilosum Tsuneki, 1979 — Antennae except scape and pedicel black (Figs 5–6); legs mostly pale brown or ferruginous (Figs 18, 25); ASR steeply inclined to PAF; hairs silvery ....................... 13 13. Clypeus largely truncated mediapically (Fig. 5); scape and pedicel brownish black; legs largely ferruginous (Fig. 18); IODs = 3:2 (Fig. 5); body length 16 mm (female). ............................................... T. cagrum Tsuneki, 1979 — Clypeus round mediapically (Fig. 5); scape and pedicel ferruginous; legs pale brown to black (Fig. 25); IODs = 5:4 (Fig. 6); body length 9 mm (male) ........................... .......................................... T. fulviventre Tsuneki, 1979

Published as part of Pham, Phong Huy, Nguyen, Anh Thi & Antropov, A. V., 2023, New records of species of the genus Trypoxylon Latreille, 1796 (Hymenoptera: Crabronidae) from northern Vietnam, pp. 58-67 in Russian Entomological Journal 32 (1) on pages 60-61, DOI: 10.15298/rusentj.32.1.07, http://zenodo.org/record/10978542