Psenulus gibbus sp. nov.

Figs 4D-4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17D, 18G, H, 19G, H, 20D, 21D

Diagnosis.

Based on a dorsally broadened interantennal carina (Figs 6D, 7D), bidentate clypeus (Figs 20D, 21D), short prescutal sutures (Figs 10D, 11D), hind tibia lacking basal spines (Figs 18G, 19G), and a well-defined pygidial plate, this species may be placed in the P. quadridentatus species group of van Lith (1962). The specimen resembles Psenulus compactus van Lith, 1962 (from Sumatra) but differs in the broadened excavation of the interantennal carina being less extensive (not extending below the antennal sockets), the subantennal carina being absent, and the mesosoma being less densely punctate. Psenulus gibbus sp. nov., superficially resembles P. ephippius sp. nov. but is readily differentiated by the yellow legs (Figs 4D, 5D) and the reticulate dorsal surface of the propodeum (Figs 14D, 15D) in the former and dark/brown legs (Figs 4C, 5C) and polished dorsal surface of the propodeum (Figs 14C, 15C) in the latter.

Material examined.

Holotype: China, Hong Kong • ♀; Mang Kung Wo; 22°22'06"N, 114°15'12"E; 60 m a.s.l.; 23 Mar.-06 Apr. 2018; C. Barthélémy leg.; Malaise trap, ref.: M405CHy4; CAS . Paratypes: China, Hong Kong • 1 ♀; ibid.; 11-25 Apr. 2020; ibid; ref.: M483CHy2; CBC • 1 ♀; ibid.; 25 Apr. 2020 - 09 May 2020; ibid; ref.: M485CHy5 • 2♀ 4♂; ibid.; 09 Mar. 2020; same collector; hand net, refs: 0708AHy1, 0708AHy2A, 2B and 2C; CAS and CBC • 1 ♀; ibid.; 10 Mar. 2020; ibid.; ref.: 0709AHy1; CBC • 1♀ 1♂; ibid.; 13 Mar. 2020; ibid..; refs: 0710AHy1 and 0710AHy2; CBC .

Standard ratios.

Male (n = 4): L = 5.9-6.9 mm (mean = 6.3 mm); CR = 1.24-1.27 (mean = 1.26); OOR = 0.48-0.76 (mean = 0.64); FLR = 1.08-1.19 (mean = 1.14); FRR = 0.66-0.74 (mean = 0.71); MR = 1.41-1.59 (mean = 1.50); OMR = 0.82-0.92 (mean = 0.88); PR = 0.35-0.62 (mean = 0.49); PFR = 1.15-1.30 (mean = 1.20). Female (n = 6): L = 6.8-8.4 mm (mean = 7.55 mm); CR = 1.32-1.4 (mean = 1.36); OOR = 0.62-0.75 (mean = 0.67); FLR = 1.28-1.57 (mean = 1.44); FRR = 0.65-0.79 (mean = 0.73); MR = 1.30-1.64 (mean = 1.44); OMR = 0.82-0.93 (mean = 0.86); PR = 0.4-0.88 (mean = 0.66); PFR = 1.13-1.28 (mean = 1.18).

Description.

Male: Antenna with tyloids on F1 to F11. Ventral margin of clypeus with two rounded teeth separated by a rounded emargination (Fig. 21D), remainder of the ventral margin straight for half of width, terminated on last third with a rounded lobe intersecting eye margin; dorsal margin concave on the central third of transverse width of clypeus, remainder reaching ventral margin along a shallow convex line. Subantennal carina well developed nearly reaching toruli (Fig. 7D); interantennal carina dorsally moderately broadened and slightly excavated on its basal part only (Fig. 9D). Mesosoma with very small largely interspaced punctures bearing numerous long and fine appressed setae; mesoscutum with the same texture (Fig. 11D); prescutal sutures extending beyond anterior level of tegula; episternal sulcus broadly foveolate (Fig. 13D), mesopleural suture simple; propodeal enclosure well defined with large fovea (Fig. 15D). Propodeum laterally and posteriorly weakly reticulate with long appressed setae, dorsal half polished with very small and largely interspaced punctures (Fig. 15D). Petiole subcylindrical, T1 low (Fig. 5D). Hind tibia without denticles dorsobasally (Fig. 19G). Pygidial plate simple (Fig. 17D). Fore wing (Fig. 19H) with first recurrent vein more or less interstitial with first and second submarginal cells, second recurrent vein meeting third submarginal cell at about 1/5 (0.18 ×) of cell length from base.

Head entirely black with appressed silvery pubescence (Figs 7D, 9D); antenna with scape mostly yellow, venter of pedicel and venter of flagellum of a lighter brown, dorsum of pedicel and remainder of flagellum dark brown; mandible black on the apical third, the remainder yellow. Mesosoma entirely black (Fig. 7D) but pronotal lobe and tegulae dark yellow/red. Trochanter, femurs, tibiae and tarsus yellow/orange, coxae black. Petiole black, remainder of metasoma mostly reddish but T2-T5 and S3-S7 with large dark brown/black areas (Fig. 7D).

Female: Ventral margin of clypeus with two relatively sharp teeth separated by a sub-triangular emargination (Fig. 20D), remainder of the ventral margin straight for half of width, terminated on last third with a blunt lobe intersecting eye margin; dorsal margin flattened for central third of transverse width of clypeus, remainder reaching ventral margin along a shallow convex line. Subantennal carina absent (Fig. 6D); interantennal carina dorsally broadened and deeply excavated (Fig. 8D); Mesosoma with very small largely interspaced punctures bearing numerous long and fine appressed setae; mesoscutum with the same texture (Fig. 11D); prescutal sutures short, not extending beyond anterior level of tegula (Fig. 10D) episternal sulcus broadly foveolate (Fig. 13D), mesopleural suture simple; propodeal enclosure well defined with large fovea (Fig. 15D). Propodeum laterally and posteriorly weakly reticulate with long appressed setae, dorsal half polished with very small and largely interspaced punctures (Fig. 15D). Hind tibia with a cluster of 7-9 short brown denticles dorsobasally, but no spines (Fig. 18G). Petiole subcylindrical, T1 low (Fig. 5D). Pygidial plate with faint ventrolateral carinae extended basally (Fig. 16D). Fore wing (Fig. 18H) with second recurrent vein meeting third submarginal cell at about 1/5 (0.22 ×) of cell length from base.

Etymology.

Specific name derived from the prominent hump [= Psenulus gibbus in Latin] formed by the interantennal ridge, extending below the antennal sockets and ending at middle of toruli.

Notes.

By its marked differences with the other known Psenulus of similar coloration as detailed in the diagnosis section, we have concluded that this is in fact a new species to science.

The first collection of this species occurred in 2019 and thus far the distribution of this species is limited to a single location in Mang Kung Wo, which is the sampled site with the highest anthropogenic disturbance. In March 2020 a series of seven specimens (four males and three females) were collected by hand net. Nonetheless, this species is one of the least common Psenulus encountered in Hong Kong. With the limitations presented above, knowledge about its activity period is limited to March (W11-W13) and April (W15-W17).