Zethus trimaculatus Cameron, 1904

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 : 530-533

Zethus trimaculatus Cameron, 1904

( Figs. 1–6 excluding 4-2)

Cameron, 1904, Zeit. Syst. Hym. Dipt., 4(1): 14–15, “ Sikkim ” (holotype BMNH).

Giordani Soika, 1941, Boll. Soc. Veneziana Stor. Nat. Mus. Civ. Stor. Nat., 2(3): 213–214, fig. 16–3, 216 (key). Giordani Soika, 1958, Boll. Mus. Civ. Stor. Nat. Venezia, 11: 75 (key).

Material examined. Holotype, ♀, Darjeeling (West Bengal, India), Cameron, Coll., B. M. type, Hym. 18. 101.

Diagnosis. Macropunctures of integument mainly foveate and dense; antennal scapes not broadened toward apex. Notaulix incomplete and distinct only at apical 1/2 of scutum. Medial part of mesopleura strongly raised and plateau-like; propodeal lamella weakly scleritized, yellowish brown coloured and circularly shaped. Apical lamellae of T2 & T3 short and erected; T 1 in lateral view with dorsal margin obtusely curved between basal stem and apical expansion; apical expansion of T1 rectangular in dorsal view with both sides nearly straight; T1 with VFB glabrous, S1 with BS glabrous, S 2 in lateral view roundly angulate at basal 1/3 and nearly straight at apical 2/ 3. Male clypeus with broad yellow band on apical margin, FXI bullet-shaped, as long as wide and shorter than FX (cf. Nguyen & Carpenter 2016).

Redescription of holotype (female, Fig. 1 )

Structure. Head: Clypeus gently convex and about 1.7 times as wide as high, apical margin smoothly curved with apex narrowly and weakly emarginate ( Fig. 5 ). Antennal scapes nearly straight and distinctly shorter than mandibles. OD a little shorter than the diameter and distinctly longer than the radius of antennal socket, ocellar area not raised. Occiput carina well develop and complete (extend to base of mandibles), weak dorsally. Gena in profile a little wider above than below, with broadest part slightly narrower than upper part of compound eye, posteroventral corner of gena obtusely curved ( Fig. 2 ). Mandible with three blunt teeth, apical tooth more pointed and slightly larger; out surface of mandible obscurely macropunctate with several longitudinal and low ridges.

Mesosoma: Pronotum smoothly narrowed forward, anterior margin straight, humeral angles obtuse. Pronotal lamella weak laterally and indiscernible dorsally. Subhumeral area weakly depressed. Notaulix incomplete, broad and deep apically, diminished gradually forward to basal 1/2 of scutum. Tegula oval, outer margin smoothly curved; posterior lobe of tegula triangular and well developed, about 1/2 as long as anterior broad part of tegula ( Fig. 3 ), apex acute, reaching far beyond parategula and slightly beyond anterior margin of auxiliary fossa. Parategula small, about three times as large as adjoining macropunctures. Mesopleura abruptly convex medially and plateau-like, epipleural and pleural sutures faintly discernible only by lines of closely adjoining macropunctures. Scutellum rectangular and flat, anterior margin adorned with a transverse row of eight pits. Metanotum narrow and belt-like, with distinct anterior furrow and lateral longitudinal keels, posterior side vertical. Propodeum broadly concave on posterior depression, dorsal side inclined outward and separated from lateral sides by weak lateral carinae; submedian carina indiscernible, median ridge of posterior depression strong and erect, dorsal propodeal aperture round. Propodeal lamella circular in shape and weakly scleritized ( Fig. 4-1 ), propodeal valvulae rectangular and well separated from propodeal lamellae. Posterior margin of hind tibia adorned with a row of widely spaced and short spines.

Metasoma: T2, T3 and S2 with smooth apical lamellae, weak on S2 and erected on T2 & T3. T1 petiolate, distinctly shorter than T2, dorsal margin obtusely curved in profile between basal stem and apical expansion; apical expansion nearly rectangular in dorsal view, with both lateral and dorsal margins nearly straight. Dorsal side of T1 distinctly depressed sub-apically with apical margin weakly swollen, smooth and shining. T1with VFB wider than BS of S1. S1 exposed and flask-shaped, differentiated into a slender BS and an abruptly broadened AE. 2nd metasomal segment sessile and a little longer than wide, T2 smoothly curved dorsally, S2 roundly angulate in profile at basal 1/3 with apical 2/3 nearly straight. T3 broadly depressed before apical lamella, S3 gently and broadly protruding posteriorly.

Integumental sculptures. Body with deep and dense foveate macropunctures on head, pronotum, basal half of scutum and mesopleura, shallower on gena and tend to become reticulate on apical half of scutum and scutellum; scutal area between notaulix deeply macropunctate. Subhumeral area transversely sulcate on lower half, epicnemium smooth and shining, posterior depressed part of mesopleura coriaceous. Metanotum sparsely macropunctate on both dorsal and posterior sides. Propodeum with lateral sides mainly coriaceous and obscurely and sparsely macropunctate near upper margin, dorsal side striate at outer half and rugose at inner half; posterior depression of propodeum broadly and transversely sulcate. T1 densely foveate with foveae tend to join to each other, VFB glaborous. S1 glabrous at BS and obscurely rugose at AE. T2 shallowly and moderate-spaced macropunctate dorsally and sparsely micropunctate laterally, punctation become denser before apical lamella, S2 sparsely micropunctate. T3 and T4 coriaceous basally and deeply and elongately macropunctate apically, subapical depression of T3 smooth and shining. T5 and S3–S5 moderate-spaced micropunctate, T6 coriaceous.

Body markings. Body mainly black, dark yellowish brown on antennal flagellomeres, legs, except coxa, and T5 & T6, yellowish brown on tegula, propodeal lamellae and valvulae. Body orange-coloured as follows: paired transverse middle spots on dorsal side of pronotum, a transverse line of three irregular spots on metanotum, and apical ring of T1. Wings transparent, palely enfumed at costal area of forewings.

Pilosity. Hairs whitish or pale yellowish brown with length a little longer than OD, very sparsely present all over. Hind tibia with dense and yellowish pubescence on inner side.

Remarks. The holotype of Z. trimaculatus is female and was collected from Darjeeling, West Bengal in northeastern India. The male was recently reported by Nguyen & Carpenter (2016) from Vietnam; according to their description, the male was characterized by a broad yellow band running along anterior margin of clypeus and a short, bullet-shaped FXI. Although Lang San (a.s.l. 350m, Na Ri District, Bac Can Province) where the male was collected is more than 1.500km away from and much lower in elevation than Darjeeling (a.s.l. 2042m), the distinct features of the male that Nguyen & Carpenter have mentioned, i.e. rounded propodeal lamella and angulate lateral contour of S2 at basal 1/3, fit well with those of the female type. Gusenleitner (2011) reported also one pair of Z. trimaculatus from Laos but did not give any comment on them. The authors have examined this pair now deposited in OLM and found them possess both round propodeal valvulae that are broadly attached basally to propodeal lamellae ( Fig. 4-2 ) and a dorsally rounded propodeal orifice. According to Bohart & Stange (1965) and Hermes et al. (2014), these character states does not belong to Zethus but more likely to Discoelius Latreilli. The status of this pair will be reviewed and clarified in another article and is not discussed here further.

Figures

FIGURES 1 – 6. Zethus trimaculatus, holotype female except 4 - 2. 1, habitus, lateral; 2, head, lateral; 3, left tegula, dorsal; 4 - 1, propodeum, lateral, 4 - 2, Discoelius. sp., female, Ban Saleui, Laos. 5, clypeus; 6, metasomal petiole, ventral and partly omitted.