Three new species of the genus Zethus Fabricius, 1804 (Hymenoptera, Vespidae, Eumeninae) from China, with an updated key to the Oriental species

Three new species, namely Zethus striatus sp. nov., Z. asperipunctatus sp. nov. and Z. nullimarginatus sp.  nov. from China are described and illustrated. Z. tumidus Nguyen & Carpenter, 2016 and Z. angulatus Nguyen & Carpenter, 2016 are newly recorded from China. An updated key to the Oriental species of the genus is provided.

striae and lateral carina, its dorsolateral surface with distinct and oblique striae and strong longitudinal carina along submedian carina, posterior surface of propodeum with transverse striae along median carina, submarginal carina produced into lamella above propodeal valvulae, its lateral surface with punctures along lateral carina and weak striae on its lower half (Fig. 7); orifice more or less angled dorsally (Fig. 6).
Metasoma. T1 about 2.5× as long as wide in dorsal view, gradually widening from one-third of the base, then nearly parallel-sided apically, with maximum width 3× its basal width, without medial carina, T1 with deep and dense macropunctures and sparse setae (Fig. 10), lateral carina of T1 present in ventral view (Fig. 11); BS of S1 with median longitudinal carina and narrow from its middle to apex, coarsely punctate on apical margin of BS and base half of AE (Fig. 11); T2 without petiole and with developed apical lamella, about 1.2× as long as wide in dorsal view, T2 with deep and dense punctures (Fig. 12); S2 swollen from the base to near midpoint, subsequent portion nearly straight in profile (Fig. 8), its apical margin with lamella; T3 with developed and raised apical lamella (Figs 8,9,12); subsequent terga and sterna with deep punctures, but slightly smaller than those on T2.
Male. Unknown. Distribution. China: Guangxi. Remarks. The species is similar to Z. trimaculatus Cameron, 1904 from Vietnam, Laos and India by the characters: body with dense punctures (Fig. 1), occipital carina developed laterally and weak dorsally (Fig. 4), pronotal carina weak laterally and indistinct dorsally (Fig. 5), S2 not tuberculate in profile (Fig. 8). It differs from Z. trimaculatus and all other members of the genus by the following character combination: apex of clypeus yellow, apical margin of clypeus frontally truncated (Fig. 3) and laterally cambered, BS of S1 with longitudinal carina (Fig. 11), propodeum with strong lateral carina and its dorsolateral and posterior surface with strong striae (Fig. 6).
Etymology. The specific name striatus is derived from Latin word: striatus, referring to propodeum with strong striae in dorsal view.  (Fig. 13), fore wing length 13.7 mm. Black, the following parts ferruginous: marking on dorso-inner margin of antennal socket, antennal scape lower area ventrally, pronotum in dorsal view, tegula, dot on lateral of metanotum, apical bands on T1, T2, T3 and middle of S2 (Fig. 13).

Zethus asperipunctatus
Head. Head with long setae, their length distinctly longer than 2× posterior ocellar diameter; head about 1.3× as wide as high in frontal view (Fig. 14), about 1.7× wider than long in dorsal view (Fig. 15); mandible with four blunt teeth and dense setae, its outer surface with coarse punctures; clypeus convex in lateral view and about 1.3× as wide as high in frontal view, with basal margin almost straight, minutely bi-dentate apically, depressed space between teeth with a median carina, width of truncation 1/3× width of clypeus between inner eye margins, clypeus with dense and long setae and dense punctures (Fig. 16); frons with long setae and dense punctures; vertex and gena with dense punctures; gena slightly wider than eye in lateral view and without longi- tudinal carina (Fig. 17); distance from posterior ocelli to apical margin of vertex 1.7× as long as distance from posterior ocelli to inner eye margin (Fig. 15); occipital carina complete (Fig. 15); antennal scape 2.7× as long as its apical width, A3 1.8× as long as its maximum width, A4 slightly longer than its maximum width, A5-11 wider than long, A12 bullet-shaped, as long as its basal width (Fig. 18).
Mesosoma. Length of mesosoma about 1.3× as long as wide in dorsal view (Fig. 19); pronotal carina complete, pronotum with distinct humeral angle and reticulate punctures dorsally; notaulix complete, mesoscutum with dense punctures, gradually shallow from the anterior to posterior portion; tegula smooth, with dense and short setae on its anterior and posterior lobe; epicnemial carina distinct; mesopleura with deep and dense punctures; scutellum flattened, and with shallow punctures and middle longitudinal furrow almost invisible, distance between punctures about as wide as punctures diameter; punctures on metanotum like those on scutellum, but deeper; metapleuron almost smooth; propodeum dull, with lateral carina and without submedian carina, its dorsolateral surface with reticulate striae (Fig. 20), submarginal carina produced into lamella above propodeal valvulae, lateral surface of propodeum with sparse and fine punctures (Fig. 21); orifice angled dorsally (Fig. 20).
Metasoma. T1 about 2.2× as long as wide, with medial carina from basal margin to one-third of the tergum, gradually widening from one-fourth of the base, then narrowly toward apex, with maximum width about 3.3× its basal width, T1 with coarse and dense punctures (Fig. 23) and lateral carina of T1 present wholly (Fig. 24); BS of S1 without longitudinal carina and with sparse punctures, lateral portion of AE with weak striae and sporadic punctures (Fig. 24); T2 without distinct petiole, gradually swollen from the base to midpoint and nearly straight to apex in lateral view, with developed apical lamella, about 1.3× as long as wide in dorsal view, T2 with dense punctures, which gradually sparse from the base to apex, distance between punctures on the base distinctly less than its diameter and 1-2× larger than puncture diameter on apical margin (Fig. 25); S2 swollen from the base to near midpoint, subsequent portion nearly straight in profile ( Fig. 22), punctures on the base of S2 large, punctures on subsequent portion like those on T2, but punctures on lateral portion dense, apical margin of S2 with lamella, T3 and S3 with dense and small punctures, T3 with thick apical lamella, and subsequent terga and sterna with small punctures, distance between punctures about as wide as its diameter.
Etymology. The specific name asperipunctatus is derived from two Latin words: asper and punctatus, referring to metasoma dull and with dense punctures.  (Fig. 26), fore wing length 13.5 mm. Almost black, the following parts yellow: spot on dorso-inner margin of antennal socket (Fig. 27), apical interrupted band on T1, apical complete band on T2; tegula dark brown (Fig. 29).

Zethus nullimarginatus
Head. Head wider than high, about 1.3× as wide as high in frontal view (Fig. 27), about 1.8× wider than long in dorsal view (Fig. 28); mandible with four teeth and dense setae, its outer surface with irregular punctures; clypeus convex in lateral view and about 1.6× as wide as high, with basal margin straight, apical margin near truncated, width of truncation 1/3× width of clypeus between inner eye margins, clypeus punctate-reticulate with dense long setae (Fig. 27); punctures on frons reticulate; vertex and gena with dense punctures; gena without longitudinal carina in lateral view; distance from posterior ocelli to apical margin of vertex 1.8× as long as distance from posterior ocelli to inner eye margin (Fig. 28); occipital carina complete (Fig. 28); antennal scape 2.8× as long as its maximum width, A3 1.7× as long as its maximum width, A4 slightly longer than its maximum width, A5-11 wider than long, A12 bullet-shaped, slightly longer than its basal width.
Mesosoma. Length of mesosoma about 1.4× as long as wide in dorsal view (Fig.  29); pronotal carina complete and developed, pronotum with coarse punctures dorsally, weak striae in lower lateral surface; notaulix complete, mesoscutum with dense punctures, gradually shallow from the anterior to posterior portion (Fig. 29); tegula smooth, with dense and short setae on its anterior and posterior lobe, its posterior lobe truncated (Fig. 29); mesopleura with dense punctures, slightly sparse ventrally; scutellum flattened, and with shallow punctures and weak middle longitudinal furrow; punctures on metanotum dense and coarse; metapleuron smooth; propodeum dull, with coarse surface in dorsal view and lateral carina very weak, without submedian carina (Fig. 30), its lateral surface with sporadic punctures and without striae (Fig. 31), submarginal lamella almost absent above propodeal valvulae (Fig. 32).
Metasoma. T1 about 2.5× as long as wide, with medial carina from basal margin to one-fourth of tergum, gradually widening from one-fifth of the base, then distinctly narrow toward apex, with maximum width 3× its basal width, T1 with punctures, distance between punctures about equal to the diameter (Fig. 34), lateral carina of T1 disappeared ventrally (Fig. 35); BS of S1 with sparse punctures, AE of S1 with weak and irregular striae and sporadic punctures (Fig. 35); T2 gradually swollen from the base to apical margin in lateral view, with developed apical lamella, about 1.2× as long as wide in dorsal view, T2 with sparse punctures, area between punctures with fine punctures, distance between punctures 1-2× larger than puncture diameter (Fig. 33); S2 gradually swollen from basal to apical margin in profile (Fig. 33); punctures on S2 slightly larger than those on T2, punctures on center area of S2 sparse, S2 with apical lamella; T3 with dense punctures and thick apical lamella; apical margin of S3 with dense punctures like those on T3; subsequent terga and sterna with slightly sparse micropunctures.
Etymology. The specific name nullimarginatus is derived from two Latin words: null and marginatus, referring to lateral carina of T1 disappeared ventrally.  Diagnosis. Female (Fig. 36): black, with the following parts yellow: spot on near dorso-inner margin of antennal socket and lateral carina of T1. Clypeus emarginated at basal and apical margin, clypeus punctate-reticulate and with long setae (Fig. 37); A12 bullet-shaped (Fig. 39); notaulix complete, punctures on mesoscutum gradually shallow from the anterior to posterior portion (Fig. 40); scutellum with punctures and middle longitudinal furrow; metapleuron with transverse striae; propodeum with lateral carina (Fig. 41) and transverse striae along median carina (Fig. 42), its lateral surface with large punctures in upper half (Fig. 41). T1 about 3× as long as wide in dorsal view, slightly narrow toward apical margin, T1 with coarse and deep punctures (Fig.  43); BS of S1 with longitudinal carina (Fig. 44), T2 with apical lamella, punctures on the near base of T2 denser and larger than other portion of tergum (Fig. 43); S2 with short apical lamella and obtuse angle in lateral view (Fig. 43); punctures on T3 and S3 dense and deep, T3 with thick apical lamella.
Male: structure as in female, but differing as follows: longitudinal pale yellow stripe on mandible, apical margin of clypeus deeply emarginated with the emargination forming a semicircle, A13 elongate, slightly curved (Fig. 38) (Fig. 46): black, with yellow spot on dorso-inner margin of antennal socket and brown on S1 and the base of S2. Clypeus with reticulate punctures, apical margin distinctly emarginated (Fig. 47); ocelli large, its diameter as wide as antennal socket (Figs 47, 48); occipital carina complete (Fig. 48); A13 elongated ( Fig. 49). Notaulix developed, mesoscutum with distinct punctures (Fig. 50); propodeum with lateral carina (Fig. 51), submarginal carina produced into developed lamella, its lateral surface without distinct punctures and striae and with deep and large punctures along lateral carina (Fig. 52). T1 2.4× as long as wide in dorsal view, maximum width 3× its basal width, then narrowly toward apical margin, with a medial carina which runs from basal margin to one-third of tergum, punctures on T1 large and dense (Fig. 53); BS of S1 with irregular and longitudinal striae; T2 with slightly dense punctures; T2 and S2 in lateral view gradually convex from basal to apical margin, with developed apical lamella; T3 and S3 with dense punctures; T3 with thick apical lamella.