Mesochorus ( Stictopisthus ) nigrifrons, Riedel, 2025

Mesochorus ( Stictopisthus) nigrifrons nov.sp. (figs 11, 33, 48, 66, 75)

H o l o t y p e: ( ♀) “Güzeripl. Caucasus Zapov., Kasparyan 25 VI 1976 ” ( St. Petersburg).

Paratypes: ( ♀) “ Wood, Odessa region, 25 km yu Kaushani , Les , Kasparyan 12 VI 1974 ” (St. Petersburg); ( ♀) “ SMTP, Trap 50 Coll 1223” (Stockholm); (3³³) “ Bylyia , Chit. Region , birch 22 УI 975 ” (St. Petersburg), ( ♀ 2³³) “ Turkey: Samsun University campus 41°22´N 36°11´E, 22.6.- 4.7.2014 Barták, Kubik ” (Linz and coll. Riedel); ( ♀) “ 25-28 VI 1999, Taman vill., Krasnodar reg., NNW Caucasus, leg. Osipov ” (coll. Riedel) GoogleMaps .

D e s c r i p t i o n: ♀. Body length 2.5-3.0 mm. Flagellum with 23-26 segments; 1 st flagellar segment 5.8-6.0× as long as wide and 0.6-0.7× as long as eye; 2 nd segment 4.8× and preapical segment c. 2× as long as wide. Temple strongly and roundly narrowed behind eye, dorsally 0.7-0.8× as long as eye. OED 2.0-2.2× ocellar diameter. Occipital carina complete. Face punctate, its width 1.1-1.2× combined length of face and clypeus and 1.2-1.3× eye length, with parallel sides. Malar space and ventral 0.3 of facial orbit striate. Mandible with two equally sized teeth. MI 0.8-1.0.

Mesosoma not depressed, 1.7-1.8× as long as high. Mesoscutum densely punctate medially, but almost smooth and shining laterally. Mesopleuron with ± extended fine rugosity centrally, with very sparse coarse punctures ventrally and dorsally. Scuto-scutellar groove moderately widened, sometimes with fine longitudinal ridges. Propodeum completely carinate, but area basalis and area superomedia confluent. Area superomedia 2× as long as wide; costula reaching at its middle. Area petiolaris hexagonal, as long as wide or slightly longer. Hind femur 4.0-4.4× as long as wide. Areolet sessile frontally; vein 1cu-a strongly postfurcal by 0.7-1.3× its length. Pterostigma 3.0× as long as wide; distal part of metacarpus about as long as width of pterostigma.

1 st tergite 2.3-2.7× as long as wide; postpetiole coarsely aciculate. 2 nd tergite 0.8-0.9× as long as wide. Thyridium large, transversely oval, at base of tergite. Ovipositor sheath stick-shaped, 8.2-8.7× as long as wide and 0.8-0.9× as long as hind metatarsus, slightly bent upwards at apex.

Color: black. Face, stemmaticum and occiput brownish; orbits widely yellowish; malar space and mandible (except teeth) yellow to cream-yellow. Scape, pedicel, and 1 st flagellomere (sometimes also 2 nd flagellomere) yellowish, following flagellomeres fuscous. Mesosoma black; pronotum brownish, its margins paler. Metasoma brownish; 1 st tergite black; 1 st sternite rufous basally; 2 nd tergite with a triangular yellowish spot in the apical 0.3-0.4. 3 rd tergite brown to black, following tergites blackish, 6 th and 7 th tergites sometimes brownish. Legs yellowish; hind coxa brown; hind femur sometimes slightly darkened; hind tibia in apical 0.15 infuscate; hind tarsomeres yellowish, with brownish tips. Pterostigma hyaline to ochreous-yellow.

³. Body length 2.2 mm. Flagellum with 26-27 segments; 1 st flagellar segment 0.73× as long as eye. Temple strongly narrowed behind eye, dorsally 0.8× as long as eye. OED 1.3× ocellar diameter. Facial width 1.0× combined length of face and clypeus and 1.1× eye length. MI 0.8. Mesosoma 1.7-1.8× as long as high. Mesopleuron punctate, with a small finely rugose central area. Hind femur 4.4× as long as wide. Pterostigma 3.0× as long as wide; vein 1cu-a strongly postfurcal by 0.8× its length. Stylet slightly clubbed at apex.

Color: Black. Face, mandible, clypeus, gena and orbits, scape, pedicel and basal two flagellomeres yellowish or reddish-yellow. Stemmaticum, occiput, vertex and flagellum distally brown. Mesosoma dark brown; pronotum, mesopleuron and metapleuron brownish-yellow. Metasoma brown; 1 st sternite reddish at base; 2 nd tergite pale yellow, with basolateral brown stripes; 3 rd tergite with central yellow spot in the basal 2/3. Legs yellow; hind coxa reddish-yellow; hind tibia and tarsomeres with narrow darkened apices; distal hind tarsomere brown. Pterostigma hyaline.

R e m a r k s: This new species is closely related to Mesochorus ( Stictopisthus) formosus BRIDGMAN , but differs by the strongly narrowed temple and partly rugose mesopleuron.

D i s t r i b u t i o n: Sweden, Russia, Turkey, Ukraine.