Taxonomic review of the genus Zethus Fabricius (Hymenoptera: Vespidae: Eumeninae) from Vietnam with descriptions of four new species Author Lien Thi Phuong Nguyen Author James M. Carpenter text Entomological Science 2016 2016 1 9 journal article 10.1111/ens.12218 03a6dd3f-a52a-4d60-bc0d-944c00931276 269807 Zethus angulatus Nguyen & Carpenter , sp. nov ( Figs 13–18 ) Figures 8–12 Zethus trimaculatus , ♂. 8 Head, frontal view. 9 Right antenna. 10 Propodeum. 11 TI & II, dorsal view. 12 Metasomal segments I & II, lateral view. Scale bar, 1 mm. Holotype , ♂ , “ VIETNAM , Bac Vang ranger station, Na Hang natural reserve, Na Hang, Tuyen Quang, 22 ° 20 ’ 52.6 "N 105 ° 25 ’ 49 "E , ca 120 m , 10 .vi. 2015 , LTP Nguyen , DD Nguyen & LX Truong ” [ IEBR ]. Paratype : VIETNAM : 1 ♀ , Huc Nghi, Dakrong, Quang Tri , 350 – 400 m a.s.l., 18 .vii. 2004 , Insect Systematic Department ’ s collectors [ IEBR ]. Figures 13–18 Zethus angulatus sp. nov. Holotype ♂ (13–17). 13 Head, frontal view. 14 Right antenna. 15 Propodeum, dorsal view. 16 TI & II, dorsal view. 17 Metasomal segments I & II, lateral view. 18 ♀, Head, frontal view. Scale bar, 1 mm. Description Male . Holotype . Body length 15 mm ; forewing length 12 mm . Structure as in Zethus dolosus , but differs as follows: body covered with shorter hairs. Head in frontal view wider than high, 1.5 × as wide as high ( Fig. 13 ). A short longitudinal carina present at one-third of the length of the gena from base. Inner eye margins in frontal view 1.1 × further apart from each other at vertex than at clypeus. Clypeus in frontal view 1.5 × as wide as long, emarginated at basal margin and slightly concave medially, apical margin deeply emarginated medially with the emargination forming a semicircle ( Fig. 13 ), with a blunt teeth laterally, width of the emargination about 1 / 4 width of clypeus between inner eye margins. Mandible with four teeth, the third tooth short and wide, with inner side round. Antennal scape 2.6 × as long as its maximum width; FI 1.6 × as long as its maximum width, FII – IV longer than wide, FV – VIII wider than long, FIX smaller than FVIII , as long as wide, FX small, FXI elongate, slightly curved, 3 × as long as it basal width ( Fig. 14 ). Mesoscutum and scutellum in lateral view more convex than in Z. dolosus . Propodeum with some strong and slightly oblique carinae along median carina ( Fig. 15 ). Metasomal segment I proportionally shorter than in Z. dolosus , 3 × as long as wide, in dorsal view gradually widening from one-fifth of the distance from base, then slightly narrowly toward apical margin ( Fig. 16 ), with maximum width 2.6 × its basal width, with a medial carina which runs from basal margin to one-third of the tergum, swollen part 2 × as long as wide in dorsal view. TII in lateral view strongly concave near base, then gradually swollen to midpoint and nearly straight to apical margin. SII in lateral view slightly concave near base, angular at basal half with obtuse angle, then nearly straight to apical margin ( Fig. 17 ), with apical lamella short. Color. Black. A longitudinal stripe on mandible, two small spot between antenna and two marks at lateral margins of TI yellow. Propodeal valvulae dark brown. Female. Body length 16.5 mm ; forewing length 13 mm . Structure as in male, but differing as follows: head in frontal view 1.3 × as wide as high ( Fig. 18 ). Ocelli small, frontal ocellus with diameter nearly half diameter of antennal socket, area around ocelli strongly swollen, projecting over posterior ocelli. Distance from posterior ocelli to apical margin of the vertex 2.7 × the distance from posterior ocelli to inner eye margin. Inner eye margins in frontal view 1.1 × further apart from each other at vertex than at clypeus. Clypeus in frontal view 1.5 × as wide as high, apical margin thick, emarginated medially, forming short and sharp tooth each lateral side, apical part between two teeth slightly produced, forming a small tooth, width of emargination 1 / 3 × width of clypeus between inner eye margins ( Fig. 18 ). Mandible with four distinct teeth on inner side, basal tooth short and pointed apically. Antennal scape 3 × as long as its maximum width; FI 1.4 × as long as its maximum width, FII – IX wider than long, FX bullet-shaped, as long as its basal width. Color. As in male, except for mandible black entirely. Distribution . Vietnam : Tuyen Quang, Quang Tri. Remarks. This species can be distinguished from its congeners by the combination of the following characters: apical margin of clypeus strongly emarginated medially with the emargination semicirclular and width of the emargination 1 / 4 width of clypeus between inner eye margin, TI 3 × as long as wide, swollen part 2 × as long as wide in dorsal view, TII in lateral view strongly concave near base, then gradually swollen to midpoint and nearly straight to apical margin, SII in lateral view slightly concave near base and angular at basal half with obtuse angle. Etymology. The specific name refers to the obtuse angle in SII.