Chalybion Dahlbom 1843

Genus Chalybion Dahlbom, 1843: 21 Type species: “ Chalybion caeruleum ” [= Sphex caeruleus of Linnaeus, 1767: 941 = Sphex caeruleus Linnaeus, 1763 (nec Sphex caeruleus Linnaeus, 1758) = Sphex cyaneus Fabricius, 1775 (nec Sphex cyaneus Linnaeus, 1758) = Pelopeus (sic) californicus de Saussure, 1867], designated by Patton, 1880: 378. Chalybium Agassiz, 1846: 77. Emendation of Chalybion Dahlbom, 1843. Chalybium W. Schulz, 1906: 192. Emendation of Chalybion Dahlbom, 1843, junior homonym of Chalybium Agassiz, 1846. Hemichalybion Kohl, 1918: 79. Type species: Pelopoeus eckloni Dahlbom, 1845, designated by Pate, 1937: 30. Key to the Vietnamese species of Chalybion Females 1. Anterior margin of clypeus with broadly projecting median lobe; antenna ferruginous; petiole wholly yellow; legs partly yellow; metasoma black; pubescence of head and mesosoma black (subgenus Hemichalybion)........ C. sumatranum (Kohl, 1884) - Anterior margin of clypeus with three or five teeth medially; antenna black and blue or green; metasoma, petiole and legs wholly blue or green, pubescence of head and mesosoma white (subgenus Chalybion)............................... 2 2. Lower metapleuron with conspicuous carina above midcoxa; area between antennal sockets with transverse carina; tarsi with plantulae............................................................................................ 3 - Lower metapleuron without conspicuous carina above midcoxa; area between antennal sockets without transverse carina; tarsi without plantulae..................................................................................... 5 3. Mesosoma less than three times as long as high; petiole longer than hind basitarsus; forewing hyaline.................................................................................................... C. gracile Hensen, 1988 - Mesosoma elongate, more than three times as long as high; petiole shorter than hind basitarsus; forewing light brown...... 4 4. Clypeus with longitudinal carina (Fig. 7); inner eye margin conspicuously curved dorsally (Fig. 7); vertex behind posterior ocelli conspicuously sloping (Fig. 8); occipital carina lowered far from apical area (Fig. 8); sterna III and IV largely covered with dense, brown micro-pubescence (Fig. 10); apical edge of fourth sternum not depressed (Fig. 10); terminal metasomal sternum somewhat curved apically (Fig. 10); body dark blue (Fig. 11); head and mesosoma not iridescent (Figs 7–9)................................................................................... C. dolichothorax (Kohl, 1918) - Clypeus without longitudinal carina (Fig. 18); inner eye margin conspicuously curved at middle (Fig. 18); vertex behind posterior ocelli moderately sloping (Figs 19, 20); occipital carina highly raised near apical area (Figs 19, 20); sterna III and IV not covered with brown micro-pubescence (Fig. 23); apical edge of fourth metasomal sternum conspicuously depressed (Fig. 23); terminal metasomal sternum widely flat apically (Fig. 23); body dark green (Fig. 24); head and mesosoma iridescent (Figs 18–21)................................................................... C. iridescens Pham & Ohl, sp. nov. 5. Metasomal sternum VI flat and wide, broadly truncate at apex.................................................. 6 - Metasomal sternum VI not markedly wide, rounded at apex.................................................... 7 6. Both forewing and hindwing brown distally, hyaline proximally; petiole moderately curved...... C. malignum (Kohl, 1906) - Both forewing and hindwing light brown; petiole markedly curved.................... C. tanvinhense Pham & Ohl, 2019 7. Propodeum without tomentum anterolaterally; petiole markedly curved................... C. japonicum (Gribodo, 1882) - Propodeum with tomentum anterolaterally; petiole moderately curved................... C. bengalense (Dahlbom, 1845) Males Males of C. sumatranum, C. dolichothorax, C. iridescens sp. nov., and C. gracile are unknown and not included. 1. Anterior margin of clypeus without teeth; flagellomeres VIII and IX with placoids; petiole markedly curved....................................................................................... C. tanvinhense Pham & Ohl, 2019 - Anterior margin of clypeus with five teeth; placoids varied; petiole moderately to markedly curved.................... 2 2. Anterior margin of clypeus with five rather small teeth; both forewing and hindwing brown distally, hyaline proximally.................................................................................... C. malignum (Kohl, 1906) - Anterior margin of clypeus with five broad teeth; wings uniformly coloured....................................... 3 3. Flagellomeres VII or VIII to IX with placoids; propodeum without tomentum anterolaterally; petiole conspicuously curved.............................................................................. C. japonicum (Gribodo, 1882) - Flagellomeres V or VI to IX with placoids; propodeum with tomentum anterolaterally; petiole moderately curved..................................................................................... C. bengalense (Dahlbom, 1845)