Orancistrocerus thanghen, Nguyen & Nguyen & Dang, 2024

Nguyen, Lien Thi Phuong, Nguyen, Anh D. & Dang, Hoa T., 2024, The solitary wasp genus Orancistrocerus from Vietnam, with descriptions of two new species (Hymenoptera, Vespidae, Eumeninae), ZooKeys 1193, pp. 95-110 : 95

Orancistrocerus thanghen sp. nov.

Fig. 1A-G

Material examined.

Holotype. Vietnam • ♀; Cao Bang, Tra Linh, Thang Hen lake ; 22°45'48"N, 106°17'38"E; alt. 611 m; 3.viii.2022; Lien Thi Phuong Nguyen, Cuong Quang Nguyen, Ngat Thi Tran leg.; IEBR.

Paratypes. Vietnam • 4♀♀, same data as holotype • 1♀; Cao Bang, Tra Linh, Thang Hen Lake ; 22°45'47.5"N, 106°17'35.7"E; alt. 619 m; 18.xi.2023; Lien Thi Phuong Nguyen, Duc Anh Nguyen, Ngat Thi Tran leg.; IEBR .

Diagnosis.

This species can be distinguished from other species in the genus in the following combination of characters: head in frontal view subcircular, 1.1 × as wide as high; occipital carina slightly widened laterally; clypeus in frontal view 1.2 × as wide as high, apical margin deeply emarginated medially, forming blunt tooth on each side, distance between teeth ~0.5 × width of clypeus between inner compound eye margins; mesoscutum shorter than wide between tegulae; TI in dorsal view ~2.2 × as wide as long; TII densely punctate, interspaces larger (~1.5 ×) than puncture diameter.

The new species is similar to O. altus in that both have TII densely punctate, interspaces larger (~1.0-1.5 ×) than puncture diameter, the occipital carina slightly widened laterally, mesoscutum slightly shorter than wide between tegulae, propodeum with border between dorsal and lateral surfaces rounded, dorsal and posterior surfaces angled. It differs from O. altus in the following characters: head in frontal view 1.1 × as wide as high (head in frontal view 1.3 × as wide as high in O. altus ), clypeus in frontal view 1.2 × as wide as high (clypeus in frontal view nearly as wide as high in O. altus ), apical margin of clypeus shallowly emarginate with distance between teeth of clypeus about half width of clypeus between inner compound eye margins (apical margin of clypeus deeply emarginate, half-oval-shaped, distance between teeth of clypeus less than half width of clypeus between inner compound eye margins in O. altus ).

Description.

Female (Fig. 1G ): body length 13.0-14.0 mm (holotype = 13.5 mm); forewing length 12.0-13.0 mm (holotype = 12.5 mm).

Structure. Head in frontal view subcircular, 1.1 × as wide as high (Fig. 1A ). Vertex produced behind posterior ocelli, then sloping down towards occipital carina, with cephalic foveae small, bearing dense pubescence, situated on depressed area on vertex behind posterior ocelli, and with distance between foveae slightly greater than diameter of median ocellus. Distance from lateral ocelli to apical margin of vertex 2.5 × distance from lateral ocellus to inner compound eye margin (Fig. 1B ). Gena in lateral view narrower than compound eye, ~0.7 × as wide as compound eye; occipital carina complete, present along entire length of gena, slightly widened laterally. Inner compound eye margins in frontal view slightly convergent ventrally, in anterior view 1.1 × further apart from each other at vertex than at clypeus (Fig. 1A ). Clypeus in lateral view gradually convex from base to apical margin; in frontal view 1.2 × as wide as high (Fig. 1A ), with basal margin slightly convex medially and distinctly separated from antennal toruli; apical margin deeply emarginate medially, forming blunt tooth on each side, distance between teeth ~0.5 × width of clypeus between inner compound eye margins. Mandible with prominent wide teeth, fourth tooth blunt apically. Scape long, ~4.4 × as long as its maximum width, slightly curved; FI ~1.8 × longer than wide, FII-III longer than wide, FIV-IX wider than long, terminal flagellomere bullet-shaped, approximately as long as its basal width. Mesosoma longer than wide in dorsal view (Fig. 1C ). Pronotal carina present, rounded at humeral angle, reaching ventral corner of pronotum. Mesoscutum slightly convex, shorter than wide between tegulae, length ~0.9 × width, with depressed and parallel furrows apically (depression exceptionally inconspicuous and hard to recognize in holotype and three paratypes because they fuse with large punctures), and two carinae laterally at apical one-third (Fig. 1C ), with middle narrow furrow present at basal one third. Disc of mesoscutellum slightly convex, with middle furrow present throughout (Fig. 1C ). Metanotum slightly convex. Propodeum (Fig. 1D ) conspicuously excavated medially, with posterior surface distinctly concave, at basal half of median carina running to apical margin; border between dorsal and lateral surfaces rounded, posterior and lateral surfaces angled. TI in dorsal view narrower than TII, truncate at base (Fig. 1F ); anterior vertical surface of TI slightly convex, with sparse shallow punctures, clearly separated from posterior horizontal surface by carina. TI in dorsal view ~2.2 × as wide as long; TII in dorsal view ~1.2 × wider than long (Fig. 1F ); SII in lateral view depressed basally, then gradually and slightly convex to apical margin.

Sculpture. Clypeus with coarse punctures on disc; border between punctures raised to form longitudinal striations medially, with smaller and deeper punctures laterally. Mandible with row of punctures laterally. Frons densely covered with coarse, flat-bottomed punctures, interspaces between punctures narrow and raised to form reticulation. Vertex and gena with punctures similar to those on frons; gena with several short, transverse, conspicuous striae laterally; occipital carina slightly widened laterally. Pronotum with punctures similar to those on vertex. Mesoscutum covered with flat-bottomed punctures, punctures smaller than those on vertex and usually forming row of punctures with interspaces between rows raised to form reticulations, reticulation tending to form longitudinal carina; mesoscutellum with punctures similar to those on mesoscutum, punctures on metanotum coarser than those on mesoscutum. Mesepisternum with flat-bottomed punctures, punctures coarser and larger to those on pronotum posterodorsally, smooth anteroventrally; border between posterodorsal and anteroventral parts distinct, without epicnemial carina. Dorsal part of metapleuron largely smooth and with several punctures at upper part, ventral part largely smooth, with several sparse and shallow punctures, and some short striae laterally. Propodeum with coarse, large, flat-bottomed punctures dorsally; punctures are shallower, smaller, and sparser laterally; angle between dorsal and lateral surfaces of propodeum somewhat rounded; posteriorly surface of propodeum with punctures at upper and lateral parts, and with oblique weak carina at lower part, with a large smooth area centrally. Tegulae with sparse small punctures laterally, the remaining surface with minute punctures. Metasomal segment I covered with dense, strong and well defined punctures dorsally, sparse and fine punctures dorso-anteriorly, distance between punctures on TI narrower than puncture diameter; TII with undefined punctures, punctures shallower than those on TI, punctures near apical margins deeper, larger and coarser than those on other part of the tergum, interspaces between punctures usually equal to puncture diameter at central part; TIII-V with punctures conspicuous and deep, smaller than those on TII apically; TVI with minute punctures; SII with punctures deeper and larger than those on margins of TII laterally; SIII-V with punctures smaller and shallower than those on SII; SVI with minute punctures; SI with narrow basal part smooth.

Color. Black; a narrow, curved, yellow strip near base of clypeus; yellow spots near base of mandible; antennal scape orange-yellow beneath; mandible, propodeal valvulae, and all trochanters reddish-brown. Wings brown with violet reflection; veins dark brown.

Pubescence. Body with short, sparse, yellow or silver setae except lower part of propodeum with longer and denser silver setae.

Male. Unknown.

Distribution.

Central Vietnam.

Etymology.

The specific epithet is a noun in apposition that refers to the name of the lake where the holotype was collected.

Figures

Figure 1. Orancistrocerus thanghen sp. nov., female holotype A frontal view B head, dorsal view C mesosoma, dorsal view D propodeum, posterior view E head and mesosoma, lateral view F metasoma, dorsal view G habitus. Scale bars: 1 mm.