Zethus trimaculatus Cameron , 1904

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, Entomological Science 2016, pp. 1-9 : 4

Zethus trimaculatus Cameron, 1904 ( Figs 8–12 )

Zethus 3-maculatus Cameron, 1904: 14, female “ Sikkim ” (The Natural History Museum, London).

This species is newly recorded from Vietnam. Material examined. Bac Kan: 1♂, Lang San, Na Ri, 21° 15 ’ N, 106°06 ’ E, 3 – 4.viii.2012, J Kojima, H Nugroho & LTP Nguyen.

The female of this species was described by Cameron (1904). In this study, the male is described for the first time. The male specimen we examined agreed well with the description by Cameron (1904).

Description

Male. Body length 16 mm; forewing length 14 mm. Structure (such as head and thorax, metasomal segment I petiolate, propodeum, metasomal segment II petiolate at base) as in Zethus dolosus , but differs as follows: body with coarser punctures, covered with shorter hairs. Head in frontal view wider than high, 1.3× as wide as high ( Fig. 8 ). Area around ocelli not swollen. Occipital carina developed laterally, blunter dorsally. 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 concave medially, narrowly and slightly emarginated medially at apical margin ( Fig. 8 ). Mandible with four teeth, the third and fourth teeth short and blunt. FI 2× as long as its maximum width, FII – VIII 1.5× as long as its maximum width, FIX narrower than FVIII, 1.8× as long as its maximum width, FX small, FXI short, bullet shaped, as long as its basal width ( Fig. 9 ). Dorsal surface of propodeum with oblique striae ( Fig. 10 ), bordered along posterior surface by lateral carina, propodeum with submarginal carina produced into rounded lamella above propodeal valvulae. Metasomal segment I proportionally shorter than in Z. dolosus , 2.3× as long as wide, in dorsal view abruptly widening from one-fourth basally, then nearly parallelside apically ( Fig. 11 ), with maximum width 2.7× its basal width, without medial carina, strongly transversely depressed near apical margin, swollen part 1.7× as long as wide in dorsal view, ventral margin flattened and forming with dorsal part a carina at each side of the tergum. Metasomal segment II with very short petiole at base. TII & III with strongly developed and raised apical lamella, the lamella in TIII somewhat longer than in TII. TII in lateral view concave near base, then gradually swollen to apical margin. SII in lateral view angular at one-third from base with obtuse angle, then nearly straight to apical margin ( Fig. 12 ), with apical lamella shorter than in TII, and not raised.

Color. Black. The following parts yellow: a thick band at apical margin of clypeus, large spot at base of mandible, small spot above antennal socket, antennal scape beneath, lateral mark at apical margin of TI. A yellowish-brown mark at base of front tibia.

Distribution. India (West Bengal), Laos, Vietnam (new record).

Figures

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.