Chorebus (Stiphrocera) hexomyzae, Li, Tao & Achterberg, Cornelis van, 2017

Li, Tao & Achterberg, Cornelis van, 2017, A new species of genus Chorebus Haliday (Hymenoptera, Alysiinae) parasitising Hexomyzacaraganae Gu (Diptera, Agromyzidae) from NW China, ZooKeys 663, pp. 145-155 : 145-150

Chorebus (Stiphrocera) hexomyzae sp. n. Figures 1, 2-11, 12-19, 20-21

Type material.

Holotype, ♀, (NWUX) "NW China: Ningxia Hui Autonomous Region, Shizuishan, Dawukou (N 39°06', E 106°20', 1140 m), 26.v.2015" and reared from Hexomyza caraganae Gu in twig galls on Caragana korshinskii Kom. f. Paratypes (88♀♀ 79♂♂): (GSFPM, NWUX, RMNH): 1♀, same data as holotype; 6♀♀ 3♂♂, id., but 17.v.2015; 5♀♀ 5♂♂, id., 23.v.2015; 3♀♀ 8♂♂, id., 24.v.2015; 4♀♀ 2♂♂, id., 25.v.2015; 5♀♀ 10♂♂, id., 27.v.2015; 1♀, id., 25.vi.2015; 3♀♀ 1♂, NW China: Inner Mongolia Autonomous Region, Hangjinqi (N 39°45', E 108°44', 1460 m), 22.v.2016; 4♀♀ 6♂♂, id., 23.v.2016; 1♂, id., 24.v.2016; 1♂, id., 26.v.2016; 2♀♀ 1♂, id., 27.v.2016; 1♀ 2♂♂, id., 28.v.2016; 2♀♀ 1♂, id., 30.v.2016; 2♀♀ 2♂♂, id., 31.v.2016; 1♀ 3♂♂, id., 2.vi.2016; 1♀, id., 3.vi.2016; 4♀♀ 4♂♂, id., 6.vi.2016; 1♀, id., 7.vi.2016; 1♀, id., 8.vi.2016; 2♂♂, id., 12.vi.2016; 15♀♀ 10♂♂, Inner Mongolia Autonomous Region, Dalate (N 40°17', E 109°54', 1020 m), 23-30.v.2016; 26♀♀ 17♂♂, id., 1-14.vi.2016.

Diagnosis.

Antenna with 27-34 segments; eye in dorsal view 1.1-1.2 times as long as temple; temple medium-sized and rounded ventrally, moderately densely setose with medium-sized setae and hardly protruding behind base of mandible (Figs 4, 12, 14, 16, 19); third segment (including annellus) 1.4 times as long fourth segment; mandible with four teeth, middle tooth (= t2) wide triangular, acute, much longer than both lateral teeth, with an extra protuberance on ventral side of middle tooth and ventral (= t3) tooth rather close to base of mandible resulting in apically narrowed mandible (Figs 10, 12-19); notauli nearly complete and largely smooth (Fig. 4); lateral lobes of mesoscutum largely glabrous; length of vein r of fore wing almost equal to width of pterostigma (Fig. 2); vein CU1b short of fore wing short and first subdiscal cell closed and robust; vein 3-SR+SR1 rather short and regularly bent, resulting in a robust marginal cell (Fig. 2); first tergite slightly longer than its apical width, evenly convex and longitudinal rugae not obscured by setosity, dorsope small, and dorsal carinae united and connected with median carina (Fig. 5); second tergite smooth and posterior half sparsely setose (Fig. 11); setose part of ovipositor sheath 0.05 times as long as fore wing and 0.2 times as long as hind tibia (Fig. 1).

Description.

Holotype, ♀, length of body 3.9 mm, of fore wing 3.5 mm.

Head. Transverse and shiny in dorsal view, slightly widened posteriorly (Fig. 9), width of head 1.9 times its lateral length, in anterior view subcircular (Fig. 7), and 1.1 times wider than mesoscutum; antenna 0.7 times as long as fore wing and with 30 segments, short setose but apically with few long bristles, length of third segment (including annellus) 1.4 times as long as fourth segment, length of third, fourth and penultimate segments 2.6, 1.8 and 1.5 times their width, respectively (Figs 1, 3); length of maxillary palp 0.8 times height of head; eye in dorsal view 1.1 times as long as temple (Fig. 8); eye in lateral view 1.4 times higher than wide; frons convex laterally, remotely punctulate and setose, and slightly depressed behind antennal sockets and with shallow groove in front of anterior ocellus (Fig. 9); vertex rather convex and with long setae (Fig. 8); OOL:diameter of ocellus:POL= 14:7:8; face 1.4 times wider than high, rather evenly convex, with long setae and largely smooth, sparsely punctulate and with satin sheen; clypeus largely smooth, convex and transverse, depressed and slightly concave medio-ventrally (Fig. 7); malar space absent; mandible with four teeth, middle tooth (= t2) wide triangular, acute, much longer than both lateral teeth, with an extra protuberance on ventral side of middle tooth (similar to t3) and ventral (= t3) tooth rather close to base of mandible resulting in apically narrowed mandible (Figs 10, 12-19); medial length of mandible nearly equal its maximum width and mandible ventro-basally with large flat part nearly as wide as dorsal part of mandible (Figs 12-15, 19).

Mesosoma. Length of mesosoma 1.5 times its height; pronope wide, elliptical and large; side of pronotum largely smooth, sparsely setose and finely punctulate, only posterior half of oblique groove coarsely crenulate and some crenulae anteriorly (Fig. 3); mesoscutum without lateral carina in front of tegula, but with lateral groove (Fig. 4); tegula square and large; epicnemial area crenulate; precoxal sulcus narrow and finely crenulate, its posterior third absent (Fig. 3), remainder of mesopleuron smooth; pleural sulcus smooth; episternal scrobe medium-sized, oval and connected to pleural sulcus; metapleuron largely smooth dorsally and rugulose ventrally, without specialised central area, setae directing postero-ventrally, but setae of dorsal groove directing dorsally (Fig. 3); notauli nearly complete, smooth except some fine crenulae anteriorly and posteriorly separated from long and narrow linear medio-posterior depression (Fig. 4); lateral lobes of mesoscutum largely glabrous and with satin sheen, remainder of mesoscutum largely setose; scutellar sulcus deep and wide, with 3 long carinae and 2 short ones, sulcus 4 times wider than its median length; scutellum smooth and moderately convex, superficially impressed medio-posteriorly; axilla densely setose; metanotum with long setae and with regular and complete coarse median carina (Figs 4, 5); surface of propodeum rugose, medially with some coarse transverse rugae, with open setosity leaving sculpture well visible, but postero-laterally rather densely setose, anteriorly with short and rather weak median carina and areola absent (Fig. 5).

Wings (Fig. 2). Fore wing: r:2-SR:3-SR+SR1 = 10:14:49; 1-SR+M slightly sinuate; SR1 evenly bent (Fig. 2); r approx. equal width of pterostigma and oblique; cu-a postfurcal; 1-CU1:2-CU1 = 3:11; 3-CU1 much longer than short CU1b; m-cu antefurcal, nearly straight and distinctly converging to 1-M posteriorly; first subdiscal cell 2.1 times as long as wide; M+CU1 largely unsclerotised. Hind wing: M+CU:1-M:1r-m = 30:14:13; m-cu absent; cu-a straight.

Legs. Hind coxa largely smooth, without dense dorso-basal tuft of setae but with long whitish setae (Fig. 6); tarsal claws medium-sized, almost as long as arolium and with few bristles (Fig. 6); length of femur, tibia and basitarsus of hind leg 3.6, 9.0 and 4.4 times their width, respectively; length of hind tibial spurs 0.35 and 0.40 times their basitarsus; hind basitarsus slightly widened submedially (Fig. 6).

Metasoma. Length of first tergite 1.1 times its apical width, its dorsal carinae united at basal quarter and connected with median carina, medially evenly convex and rather regular and coarse longitudinal rugae distinctly visible despite long setosity (Fig. 5); dorsope small and round, laterope obsolescent; second tergite smooth and medio-anteriorly glabrous, remainder sparsely setose; setose part of ovipositor sheath 0.05 times as long as fore wing (total visible sheath 0.08 times), narrowed apically and 0.2 times as long as hind tibia (Fig. 1).

Colour. Black (including mandible); palpi, legs (but coxa and dorsally femora black), pterostigma and veins dark brown; wing membrane subhyaline.

Male. Similar to female. Antenna with 3-4 segments more than in female and slightly slenderer.

Variations.

Length of body of ♀ 3.0-3.9 mm, and of fore wing 2.7-3.5 mm; length of body of ♂ 3.3-3.9 mm, and of fore wing 2.9-3.7 mm; antenna of ♀ with 25(1), 26(1), 27(5), 28(12), 29(19), 30(10), 31(7) segments; antenna of ♂ with 30(2), 31(6), 32(9), 33(16), 34(12), 35(1), 36(1) segments; first metasomal tergite 1.0-1.1 times longer than its apical width; setose part of ovipositor sheath 0.04-0.05 times as long as fore wing; setae of second tergite as subposterior row or also laterally present; lateral lobes of mesoscutum nearly completely glabrous or anterior third setose and remainder glabrous; femora and tibiae dark brown with blackish streaks or yellowish brown; palpi dark brown or yellowish brown; mandible black or dark brown.

Biology.

Larval endoparasitoid of Hexomyza caraganae Gu, 1991 ( Diptera : Agromyzidae ) in twig galls on Caragana korshinskii Kom. ( Fabaceae ).

Distribution.

Palaearctic China (Inner Mongolia, Ningxia).

Remarks.

The new species belongs to the subgenus Stiphrocera Foerster, 1863, because it has smooth hind coxa without a dorsal tuft, and runs in the key to Far East Russian species by Tobias (1998) to Chorebus coxator (Thomson, 1895) and C. singularis (Tobias, 1962). The new species is easily separated by its dark palpi, mandible and legs. In addition, the shape of the mandible and the mesosomal setosity are different as indicated in the key. The new species is very different from the only other named species reared from Hexomyza twig galls, the European C. gedanensis (Ratzeburg, 1852), because of the elongate first metasomal tergite and shorter vein r of the fore wing of the latter. Two similar species occurring in the East Palaearctic region ( C. ares (Nixon, 1944) and C. senilis (Nees, 1812)) are included in the key for comparison.

Etymology.

The specific name is derived from the host’s generic name: Hexomyza Enderlein, 1936.