Synergus dilatatus, Xiudan & Luan & Yang, 2024

Xiudan, Wang, Luan, Liu & Yang, Zeng, 2024, Discovery of a new species of Synergus (Hymenoptera, Cynipidae, Synergini) based on morphology and molecular data, ZooKeys 1193, pp. 81-94 : 81

Synergus dilatatus sp. nov.

Figs 2-9 , 10-17 , 18

Type materials.

Holotype. China ·♀, Hubei Prov., Suizhou County; 31.69°N, 113.38°E (DD); galls coll. 30 Jul. 2021, ex. Aug. 2021; Yang Zeng leg.; from twigs on Quercus variabilis . Paratypes. China ·5 ♀ & 2 ♂, same data as the holotype.

Diagnosis.

The new species is similar to S. formosanus Schwéger & Melika, 2015. Synergus dilatatus sp. nov. but differs from the latter by female head dark red to black (orbits, malar space and a band above clypeus chestnut brown in S. formosanus female); ventral margin of malar space expanded into a wide and recurved lamina (ventral margin not or slightly expanded in S. formosanus ); medial mesoscutal line restricted to posterior half of mesoscutum (on posterior two-thirds of mesoscutum in S. formosanus ); and parapsidal line absent (present in S. formosanus ). The attacked galls of the new species, whose surface is covered with dense tomentum, is without tubercles or spots (the attacked galls of S. formosanus are covered with small raised tubercles and purple spots).

In the key to species of Synergus from the EP presented by Schwéger et al. (2015: 458), S. dilatatus sp. nov. follows item 15 and the key should be adapted as described below:

15	Postgena with dense white setae on lower half; median mesoscutal line strongly impressed, complete, reaches anterior margin of mesoscutum	S. symbioticus Schwéger & Melika, 2015
-	Postgena mostly glabrous on lower half; median mesoscutal line strongly impressed only in posterior half, extending to 2/3 of mesoscutum length, never complete	16
16	Ventral margin of malar space expanded into a wide and recurved lamina; medial mesoscutal line restricted to posterior half of mesoscutum; parapsidal line absent	S. dilatatus sp. nov.
-	Ventral margin not or slightly expanded; medial mesoscutal line on the posterior two-thirds of mesoscutum; parapsidal line present	S. formosanus Schwéger & Melika, 2015

Description.

Female. Body length 2.4-2.8 mm (N = 14).

Color: Head reddish dark brown to black, except mouthparts yellowish brown; antenna yellowish to light brown. Mesosoma black. Legs yellowish or light brown. Wings hyaline with slightly darker coxae, veins pale yellowish. Metasoma with 1st tergite dark reddish brown and rest of metasoma reddish brown, ventral spine of hypopygium light brown.

Head (Figs 6 , 8 , 9 ): Nearly trapezoid, 1.2 times as wide as high in front view, distinctly broader than mesosoma, 2.6 times as broad as long in dorsal view. The central area of frons elevated and delimited by two dull lateral frontal carinae, the surface finely coriaceous, puncticulate, and sparsely setose; eyes 1.6 times as high as wide; height of eye 2.0 times as high as length of malar space (Fig. 6 ). Lower face, clypeus and malar space with dense, long, white setae, except area under antennal sockets sparsely setigerous. Lower face with distinct striae radiating from clypeus and reaching basal margin of compound eye and antennal toruli. Ventrolateral corner of malar space expanded as a wide and recurved lamina. Clypeus barely impressed, covered with long appressed setae; anterior tentorial pit small, distinct; clypeo-pleurostomal line and epistomal sulcus absent. Transfacial distance about the same as the height of the compound eye; distance between torulus and compound eye subequal to diameter of toruli and 1.67 times as great as the distance between toruli (Fig. 6 ). Vertex rugulose around the anterior ocellus, and from interocellar area to occiput sparsely foveolate; POL: OOL: LOL= 7: 3: 3; OOL and LOL as long as diameter of frontal ocellus (Fig. 8 ). Postgena glabrous, gular sulcus and posterior tentorial pits distinct, with slightly white setae close to posterior tentorial pits. Gena not broadened posterior to eye, and areolate-rugose (Fig. 9 ). Antenna filiform with 12 flagellomeres, slightly thickened toward apex; pedicel 1.3 times as long as broad, not broadened apically, with dense and short pubescence; placoid sensillae slightly visible on flagellar segments F3-F12. F1 about 1.2 times the length of F2 and as long as F3. Last flagellar segment 3.75 times as long as wide. Relative length from pedicel to F12: 14:12:14:14:13:13:11:12:10:9:9:15 (Fig. 4 ).

Mesosoma: slightly longer than high and 1.3 times as long as wide (Fig. 11 ). Pronotum slightly narrowed medially, median length 1/3 length of outer lateral margin; sides of pronotum angled in dorsal view (Fig. 12 ). Pronotum puncticulate medially and laterally with deep punctures. Propleuron alutaceous, with parallel longitudinal striae; pronotal lateral carina present. Mesoscutum slightly broader than long measured at anterior tip of tegulae; surface areolate-rugose, covering with dense white setae. Notaulus complete, with smooth bottom. Anterior parallel line invisible; distinct parascutal carina present; parapsidal lines hardly traceable; median mesoscutal line broadened posteriorly and never extending to anterior half of mesoscutum (Fig. 12 ). Dorsoaxillar area coriaceous, with numerous long hairs; lateroaxillar area joined by dorsoaxillar area at an acute angle. A median carina separates mesoscutellar foveae into two parts which are as long as wide, bottom hairless and coriaceous, and distinctly delimited posteriorly. Mesopleuron hairless laterally except the lower edge densely setae, fully covered with parallel longitudinal striae. Metapleural sulcus reaching posterior margin of mesopleuron in upper 1/3 of its height (Fig. 11 ). Mesopleural triangle densely pubescent. Propodeum uniformly coriaceous, pubescent; lateral propodeal carinae distinct, anteriorly flat and posteriorly thin, slightly curved; median propodeal area delicately coriaceous without setae, with few rugae posteriorly. Metanotal trough smooth, pubescent; propodeal spiracle transversely ovate. Nucha very small, with distinct longitudinal parallel rugae (Fig. 13 ).

Forewing (Fig. 16 ): Hyaline, margin with cilia; radial cell partially closed, 2.4 times as long as broad; R1 nearly straight and reaching wing margin, Rs curved distally, distinctly reaching wing margin; areolet small but distinct; Rs + M inconspicuous, not reaching basal vein.

Metasoma: About as long as head and mesosoma combined and 1.4 times as long as high; petiole sulcate; syntergite almost completely covering remaining tergites, surface smooth and mainly glabrous, with very few white setae anterolaterally, posterodorsal area with lateral patch of sparse setae and indistinct micropunctures, not extending onto lateral sides. Subsequent tergites and hypopygium micropunctate; prominent part of the ventral spine of hypopygium small, smooth with few short setae distally (Fig. 14 ).

Male (Figs 3 , 5 , 7 , 15 , 17 ). Body length: 1.5-2.3 mm (N = 4). Lower face and mouthparts yellowish brown; frons, vertex and occiput reddish brown to black (Fig. 7 ). Antenna with 13 flagellomeres, scape length 3 times as long as wide; pedicel 1.6 times as long as broad, F1 strongly curved medially and broadened apically, 1.6 times as long as pedicel and 1.2 times as long as F2; relative length of F1-13: 13:11:11:10:9:9:8:8:8:8:7:7:8; placoid sensilla slightly visible on F3-F13, increasing in number per segment distally (Fig. 5 ). Metasoma distinctly shorter than head and mesosoma combined (Fig. 3 ) and slender than female in lateral view (Fig. 15 ). Otherwise, as described for female.

Biology and galls.

All specimens were reared from two juicy, green, young galls resembling fruits, collected from shoots of Quercus variabilis on July 30, 2021. Galls are ball-shaped, with diameter 14-22 mm; surface smooth, covered with dense tomentum, without tubercles or spots. The galls became wrinkled and shriveled after inquilines emerged in late August (Fig. 18 ). Unfortunately, no gall makers emerged, so the species that formed the galls remains unknown.

Distribution.

Known only from Hubei Province (China).

Etymology.

The species is derived from Latin word " dilatatus " meaning dilated, extended, referring to the dilated gena of the new species.

Figures

Figures 18. General appearance of Synergus dilatatus sp. nov. galls on twigs of Quercus variabilis.

Figures 2 - 9. Synergus dilatatus sp. nov. 2 general habitus (♀) 3 general habitus (♂) 4 antenna (♀) 5 antenna (♂) 6 head in anterior view (♀) 7 head in anterior view (♂) 8 head in dorsal view (♀) 9 head in lateral view (♀).

Figures 10 - 17. Synergus dilatatus sp. nov. 10 head in posterior view (♀) 11 mesosoma in lateral view (♀) 12 mesosoma in dorsal view (♀) 13 propodeum in dorsal view (♀) 14 metasoma in lateral view (♀) 15 metasoma in lateral view (♂) 16 fore wing (♀) 17 fore wing (♂).