Chalybion iridescens Pham & Ohl & Nguyen & Nguyen 2025, sp. nov.

Chalybion iridescens Pham & Ohl, sp. nov. (Figs 18–24) Material examined. Holotype, VIETNAM. Gia Lai: ♀, Kon Chu Rang Natural Reserve, Son Lang, Kbang, 14°42'48"N, 108°25'24"E, 861 m, 5.v.2018, T.T. Nguyen collector. Paratypes, VIETNAM. Gia Lai: 1 ♀, same data as for holotype. Diagnosis. Chalybion iridescens sp. nov. is a member of the Chalybion madecassum species-group because of the following combination of characters: Anterior margin of clypeus with three distinct teeth; mandible without inner subapical tooth; supra-antennal plate with transverse carina ventrally; mesosoma about 3.3 × as long as high; metanotal flange small, somewhat produced over propodeum; lower metapleuron with angular carina; tarsi with plantulae; body with white pubescence. Both C. dolichothorax and “ C. iridescens ” sp. nov. differ from the other members of the C. madecassum species-group by having the following characters: Mesosoma more than three × as long as high, propodeal dorsum with pair of longitudinal furrows, and occipital carina evanescent ventrally. The new species is similar to C. dolichothorax, but the differences between them are listed in the key above and in the revised key to the species of the C. madecassum group below. Description. Female (Figs 18–24): Body length 24–25 mm, forewing length 16.3 mm. Head (Figs 18–20): In frontal view circular. Mandible without inner subapical tooth. Clypeus moderately convex, without median carina; anterior margin of clypeus with three blunt teeth, lateral tooth broader than and as long as median tooth. Frontal line present. Ocelli equal in diameter. Vertical area behind hindocelli slightly raised above eyes. Occipital carina absent ventrally. Clypeus coarsely, sparsely punctate. Frons coarsely, irregularly transversely punctatorugose. Vertex and gena finely, sparsely punctate. Long, white setae sparsely distributed on clypeus, frons and gena. Distance between hindocelli about equal to that from midocellus to hindocellus, ½ × that from hindocellus to inner eye margin, and about 4.6 × that from hindocellus to vertex margin. Flagellar ratio (length of the first flagellomere divided by that of the second flagellomere) 0.94. Orbital ratio (shortest interocular width across vertex divided by shortest interocular width across clypeus) 0.66. Clypeal ratio (length of clypeus divided by shortest interocular width across clypeus) 0.91. Hypostomal cavity ratio (length of hypostomal cavity divided by width) 0.83. Mesosoma (Figs 21, 22, 24): Conspicuously elongate, 3.25 × as long as high. Pronotum not regularly curved in lateral view, 1.4 × as wide as long, without notch at middle, and with series of transverse striae dorsally and laterally. Mesoscutum transversely striate, interspaces shallowly punctate. Mesopleuron densely punctate. Scutellum, metanotum, and metapleuron densely punctate. Propodeum densely, transversely striate dorsally and dorsolaterally, with pair of longitudinal furrows dorsally and dense punctations dorsolaterally. Legs with plantulae, tarsal claws with inner tooth. Metasoma (Figs 23, 24): Integument smooth, dull, with white pubescence. Petiole slightly curved, its length 1.8 × that of hind basitarsus. Metasomal sterna III and IV without micro-pubescence, terminal sternum rounded apically. Color (Figs 18–24): Integument dark green. Head and mesosoma with iridescent reflections. Flagellum, labial palpus, maxillary palpus, and tegula black. Mandible red in middle. Wings hyaline, forewing somewhat infuscate apically. Male. Unknown Etymology. The specific name is a Latin adjective referring to the iridescence of the species. Distribution. Vietnam: Gia Lai. Remark. Chalybion dolichothorax differs from other species of the C. madecassum species-group by a markedly elongate thorax (more than three times as long as high). Chalybion iridescens sp. nov. shares this character and, thus, is the second species with an elongate thorax in the species-group.