Zethus tumidus Nguyen & Carpenter, sp. nov (Figs 19���23) Holotype, ♂, ��� VIETNAM, Bach Ma national park, Thua Thien ��� Hue, 1200 m, light trap, 18.v. 2012, LTP Nguyen ��� [IEBR]. Paratype: 1 ♂, same data as holotype [IEBR]. Description Male. Body length 12 ��� 15 mm (holotype: 12 mm); forewing length 10.4 ��� 12.4 mm (holotype: 10.4 mm). Structure as in Z. dolosus and Z. angulatus sp. nov. but differs as follows: head in frontal view wider than high, 1.3 �� as wide as high (Fig. 19). Ocelli large, frontal ocellar diameter about as wide as the diameter of antennal socket. Inner eye margins in frontal view 1.2 �� further apart from each other at vertex than at clypeus. Clypeus in frontal view 1.3 �� as wide as long, emarginated at basal margin and slightly concave medially, apical margin strongly emarginated medially with the emargination semicirclular (Fig. 19), forming blunt teeth laterally, width of emargination nearly 1 / 5 width of clypeus between inner eye margins. Mandible with four teeth, the third and fourth teeth short and blunt. Antennal scape 2.4 �� as long as its maximum width; FI 2 �� as long as its maximum width, FII ��� VI longer than wide, FVII ��� IX wider than long, FX small, as long as wide, FXI elongate, slightly curved, 2.3 �� as long as it basal width (Fig. 20). Mesoscutum and scutellum in lateral view more convex than in Z. dolosus, and not at same level. Propodeum with strong oblique carinae along medial carina (Fig. 21), covering all of the area inside lateral carinae. Metasomal segment I proportionally shorter than in Z. dolosus, 2.4 �� as long as wide, in dorsal view abruptly widening from one-third of the segment from base, then slightly narrowly toward apical margin (Fig. 22), with maximum width 2.8 �� its basal width, with a medial carina which runs from basal margin to one-third of the tergum, swollen part 1.6 �� as long as wide in dorsal view, tergum and sternum fused, area between two sides with punctures, a longitudinal carina absent. Metasomal segment II with very short petiole at base (Figs 22,23), TII and SII in lateral view gradually convex from base to apical margin (Fig. 23), with developed apical lamella, slightly raised. Color. Black. Two small spots just above antennal sockets yellow. Distribution. Vietnam: Thua Thien ��� Hue. Remarks. This species can be distinguished from its congeners by the combination of the following characters: frontal ocellus large with diameter as wide as antennal socket diameter, apical margin of clypeus strongly emarginated medially with the emargination nearly semicircular and width of the emargination 1 / 5 width of clypeus between inner eye margin, TI short, 2.4 �� as long as wide, swollen part 1.6 �� as long as wide in dorsal view, metasomal segment II with very short petiole at base, SII in lateral view gradually convex from base to apical margin. Etymology. The specific name refers to the swollen metasomal segment I.

Published as part of Lien Thi Phuong Nguyen & James M. Carpenter, 2016, Taxonomic review of the genus Zethus Fabricius (Hymenoptera: Vespidae: Eumeninae) from Vietnam with descriptions of four new species, pp. 1-9 in Entomological Science 2016 on page 6, DOI: 10.1111/ens.12218, http://zenodo.org/record/269807