Zethus nigerrimus Gusenleitner, 2001

Lu, Sheng-Shan, 2017, New record of the genus Zethus Fabricius from Taiwan, with the description of Z. taiwanus sp. nov. and a key to the species of trimaculatus - group (Hymenoptera: Vespidae: Eumeninae), Zootaxa 4324 (3), pp. 529-540 : 536-539

Zethus nigerrimus Gusenleitner, 2001

( Figs. 16–20 , 22, 24, 27 & 28)

Gusenleitner, 2001, Linzer biol. Beitr., 33(2): 659–661, “Vinh Phu, Tam Tao (probably Vinh Phuc, Tam Dao according to Nguyen et al., 2014), N. Vietnam” (holotype NHMW).

Gusenleitner, 2012, Linzer biol. Beitr., 44(2): 1050, Hua Phan, Laos.

Gusenleitner, 2013, Linzer biol. Beitr., 45(1): 138, figs. 7–9.

Material examined. 1♀, Ban Saleui , Phou Pan Mt., 1350–1900m, E103°59'26'' N20°13'30'', Hua Phan Prov., Laos. V/6/2011, leg. C. Holzschuh & locals, det. J. Gusenleitner . 1♂, same locality as the female, VI/15/2013, leg. C. Holzschuh & locals, det. J. Gusenleitner. Both specimens were in OLM .

Diagnosis. Body almost entirely black. Female clypeus minutely bi-dentate apically, space between the teeth depressed with a middle ridge; male clypeus bi-dentate with shallow apical notch 1/6 as wide as clypeus. Male mandible with three teeth, two basal teeth small, about the same size and close to each other. Epicnemial carina strong and raised, bordered posteriorly by a narrow furrow, epipleura suture distinct. Volsella of male genitalia with broad vosellar ridge having oblong basal lobe. Volsellar ridge adorned with six or seven small, dark and setigerous teeth at ventro-inner margin and a large protrusion close to basal lobe at baso-outer corner. Aedeagus with ventral lobe of penile valve roundly shaped basally in profile, basal plate broad and equilaterally triangular with blunt apex.

Differential description. General morphology of Z. nigerrimus is similar to that of Z. taiwanus . It differs from the latter as described below.

Female. Clypeus minutely bi-dentate, space between the teeth depressed with a middle ridge (described by Gusenleitner as tri-dentate). Ocellar area not distinctly raised. Occiput carina obscurely bordered anteriorly by a row of short pits. Epicnemial carina strong and raised, bordered posteriorly by a narrow furrow; pleural suture defined by a row of seven large and deep pits, epipleural suture distinct. Propodeum with posterior depression very shallow, almost flat and finely striate transversely, submedian carina indiscernible. Apical expansion of T1 relatively longer and narrower, about 4/9 (1/ 2 in Z. taiwanus ) as wide as T2. Body punctation generally more sparser and shallower. Posterior half of gena nearly wholly smooth, scutal area between notaulix smoother and shining with only few punctures. Body almost entirely black, propodeal valvulae deep brown, yellow markings as in Z. taiwanus . Body hairs (about two OD long) mainly whitish, yellowish brown on mandibles. Hairs longer and denser on clypeus, lower side of mesopleura, outer half of posterior depression of propodeum and metasoma, except dorsal surface of T2.

Male (first reported here). Clypeus with apical notch narrower and shallower, about 1/6 as wide as clypeus. Mandible with three teeth, two basal teeth small, about the same size and close to each other. FXI slightly longer than FX, slender in shape with apex more pointed and coloured dark reddish brown as in other flagella. Propodeum with weak submedian carina and obscurely rugose lateral sides.

Genitalia (Figs. 22, 24, 27 & 28): Ventral lobe of gonocoxite short and blunt, volsellar ridge broad and expanded basally with oblong basal lobe, ventral root of digitus shorter and triangular. Volsellar ridge adorned with six or seven small, dark and setigerous teeth at ventro-inner margin and a large protrusion (not shown here) close to basal lobe at baso-outer corner. Basal lobe of digitus broader in inner view with its ventral corner distinctly exceeds cuspis. In lateral view, aedeagus with ventral lobe of penile valve roundly shaped basally and basal apodeme smoothly curved; in ventral view, basal apodeme broad at basal 1/2 with its outer margin strongly curved almost at a right angle at basal 1/3. Basal plate of aedeagus equilaterally triangular with blunt apex.

Measurements (in mm). ♀ BL 17.8, FWL 8.9, ♂ BL 14.6, FWL 11.7

FIGURES 21–28. Male genital structures. 21, 23, 25 & 26, Z. taiwanus ; 22, 24, 27 & 28, Z. nigerrimus . 21 & 22, genital capsule, ventral; 23 & 24, left volsella, inner; 25 & 27, aedeagus, ventral; 26 & 28, aedeagus, lateral. ae, aedeagus. ap, basal apodeme of ae. crv, volsellar ridge. cu, cupis. di, digitus. go, gonocoxite. lbd, basal lobe of di. lbv, basal lobe of crv. ldd, distal lobe of di. lvg, ventral lobe of go. lvv, ventral lobe of penile valve. pb, basal plate of ae. rvd, ventral root of di. vo, volsella.

Remark. Gusenleitner reported Z. nigerrimus also from Malaysia (2007) and Laos (2012). However, direct inspection on the male collected from Johor, Malaysia revealed that it belongs in fact to a different species, which has a much longer metasomal petiole and is probably undescribed.

Figures

FIGURES 16 – 20. Zethus nigerrimus, Ban Saleui, Hua Phan Prov., Laos. 16, male clypeus; 17, female left tegula, dorsal; 18, female habitus, lateral; 19, apex of male antenna, ventral; 20, male antenna, lateral.