Zethus (Zethastrum) bakeri Giordani Soika, 1995

Yeh, Wen-Chi & Barthélémy, Christophe, 2023, A taxonomic study on the genus Zethus Fabricius from Hong Kong, with proposal of a new synonym (Hymenoptera: Vespidae: Eumeninae), Zootaxa 5339 (6), pp. 520-532 : 529-531

Zethus (Zethastrum) bakeri Giordani Soika, 1995

Zethus bakeri Giordani Soika, 1995: 92 —“ Singapore ” (holotype, ♀, MSNV).

Zethus malayanus Gusenleitner, 2010: 704–705 , figs 15–19—“ Perak, Cameron Highlands , Batu, Malaysia ” (holotype, ♀, OLML), “ syn. nov. ”

Material examined. SINGAPORE — 1♀, Coll. Baker; (holotype, MSNVE) .

CHINA — Hong Kong • 1♁; Hok Tau; 22°29'25.31"N, 114°11'0.14"E; W.-C. Yeh leg.; hand net; 06 Jun. 2006; ( FACT) .

Diagnostic description. Female ( Fig. 22–26 ). Body black with yellowish tegula, tibia adorned outside with dense and long pale yellowish hair ( Fig. 24 ). Clypeus broader than long, apical margin straight ( Fig. 22 ). Tegula oval, apex slightly incurved and obtuse ( Fig. 23 ). Propodeum nearly vertical, dorsal side shallowly foveate, both lateral and submedian carinae indiscernible, bf linear ( Fig. 26 ). Abdominal Sg1 slim and long, four times as long as wide; Sg2 strongly petiolate with basal petiole around 1/4 as long as the segment ( Fig. 25 ), S3 with median part of apical margin protruding backwards, forming a crescent protuberance (as in Fig. 29 ).

Male ( Figs 27–31 ). Differing from female mainly in the following: Clypeus with a large yellow spot at middle, mandibles largely yellow ( Fig. 28 ). Antenna with F3–F9 ventrally adorned with dense and long whitish hair tufts ( Fig. 31 ), F11 bullet-shaped with apex obtusely pointed and reaching at the base of F 8 in appressed condition ( Fig. 30 ). Tegula black, hairs of tibia not especially dense and long; both Sg1 and basal petiole of Sg2 shorter ( Fig. 27 ).

Genitalia ( Figs. 33 , 35, 38, 39 ). Apex of genital capsule strongly curved inwards, volsellar ridge unarmed and nearly smooth. Cuspis long with apex reaching apex of genital capsule ( Fig. 33 ), adorned with dense thin hairs on inner side. Digitus petal-shaped, largely membranous and concave on ventral side; lbd transversely triangular and adorned with many tiny sensory cones and few short hairs, ldd finger-like and curved with rounded apex ( Fig. 35 ). Aedeagus in lateral view with lvv erect and rectangular, basally attenuating into a horn-like protuberance ( Fig. 38 ), ap roundly curved at middle, pb very short and obtuse at apex; in ventral view, apical half of lvv expanding and rounded, ap angulately incurved at basal 1/4, pb rounded ( Fig. 39 ).

Remarks: We examined the female holotype of Z. bakeri and compared it with high resolution images, the original description and figures of the holotype female of Z. malayanus . The result did not reveal any distinct difference separating them; hence, we confirm that Z. malayanus is a junior synonym of Z. bakeri . The Hong Kong male was compared with the description and figures of the Guangdong male of Z. malayanus given by Nguyen & Xu (2017) and there was no convincible evidence either that could differentiate the males from each other.

Distribution: Singapore, Malaysia, Vietnam ( Nguyen & Carpenter, 2016), China (Guangdong, Hong Kong).

Figures

FIGURES 22–26. Zethus bakeri, female holotype. 22, head in frontal view; 23, tegula; 24, female lateral habitus; 25, metasoma in dorsal view; 26, propodeum in dorsal view.

FIGURES 27–31. Zethus bakeri, male. 27, lateral habitus; 28, head in frontal view; 29, apical lamella of S3; 30 & 31, antenna.

FIGURES 32–33. Male genitalia of Zethus in ventral view. 32, Z. angulatus; 33, Z. bakeri. crv, volsellar ridge; cu, cupis; di, digitus; go, gonocoxite; lbd, basal lobe of digitus; ldd, distal lobe of digitus.

FIGURES 34–39. Male genital structures of Zethus, 34, 36, 37, Z. angulatus; 35, 38, 39, Z. bakeri. 34 & 35, left volsella, inner view; 36 & 38, aedeagus in lateral view; 37 & 39, aedeagus in ventral view. ap, basal apodeme of aedeagus; lvv, ventral lobe of penis valve; pb, basal plate of aedeagus.