Arpactophilus nyelayu sp. nov. (Figs. 12, 81–82) Diagnosis. Arpactophilus nyelayu is the only New Caledonian species in the genus with the combination of a distinctly elevated ridge on the midventral line (Fig. 12) and a well-delimited dark brown area on the metatibia (as in Fig. 8). Description. FEMALE: Total length 5.4 mm; forewing length 3.2 mm. Body black, with areas of dark yellow and brown. Dark yellow: palpi; scape; apical margin of pronotal lobe; trochanters; femora apically and basally; tibiae, except apical area on metatibia; tarsi. Brown: pedicel; flagellum; anterior pronotal margin; tegula; coxae; most of femora. Mandible reddish-black. Wings hyaline; pterostigma dark brown. Head about 1.1 × as long as wide in frontal view. Apical margin of clypeus strongly projecting medially, medioapical margin nearly straight (Fig. 81). Apical margin of labrum projecting medially, medioapical margin nearly straight. Ventral mandibular tooth about ¼–1/5 of total mandibular length, not reaching opposite mandibular base. Palpal formula 5:4. Frons colliculate and finely reticulate with a carina parallel to inner compound eye margin (Fig. 81) and dense short setae. Frontal carina present from median ocellus to midlength of clypeus, forming a flat point at basal clypeal margin. Scape 3.4 × as long as wide. Ocellar triangle anterior of tangent between upper posterior orbits of compound eyes, lateral ocelli anterior of tangent by more than their diameter. Occipital carina interrupted dorsally (Fig. 6). Gena imbricate with sparse punctation and associated setae, without tubercles, spines, or dorsoventral carina. Hypostomal midventral line carinate, faint anteriorly, strongly angulate medially (Fig. 12), with bordering short transverse carinulae on hypostomal integument. Mesosoma about 1.7 × as long as wide in dorsal view. Propodeum about 0.8 × as long as wide in dorsal view. Mesosoma imbricate with dense punctation (Fig. 82), except on dorsal surface of propodeum; lateral surface of propodeum also transversely carinulate; dorsal surface of propodeum coarsely reticulate (similar to pattern in Fig. 18). Pitted sulcus present posterior to mesoscuto-mesoscutellar sulcus. Hypersternal sulcus absent. Metafemur 2.6 × as long as wide. Metatibia with a well-delimited dark brown, flattened area apically. Pretarsal claws without teeth. Forewing with two submarginal cells; anterior border of submarginal cell II slightly shorter than posterior border. Hind wing with five distal hamuli. Metasoma polished, punctation sparse (Fig. 82). Metasomal sternum II swollen medially, forming bulge (as in Fig. 2). Pygidium with broad row of silk setae. MALE: Unknown Remarks. Arpactophilus nyelayu is similar to A. kumak, A. vamale, A. numee, A. xaragure, A. orowe, A. pwapwa, and A. arboreus as all share the combination of a dark brown or black metasoma with a bulge on the metasomal sternum II and a dark brown or black clypeus with a medially strongly projecting apical margin that has no or only a small incision medially. See remarks-section of A. kumak. Material examined. HOLOTYPE ♀: “ NEW CALEDONIA 12074: 22°19’S x 166°55’E, 480m, Foret Nord, site 1. 22 Dec 2004– 9 Jan 2005. Burwell, Wright. Malaise, rainforest” [QM]. Etymology. The specific epithet is taken from the name Nyelâyu, one of the New Caledonian native languages. It is treated as a noun in apposition.

Published as part of Breitkreuz, Laura C. V., Ohl, Michael & Engel, Michael S., 2016, A review of the New Caledonian Arpactophilus (Hymenoptera: Crabronidae), pp. 1-66 in Zootaxa 4063 (1) on pages 38-40, DOI: 10.11646/zootaxa.4063.1.1, http://zenodo.org/record/270412