Penthetria nigra Statz, 1943

Skartveit, John & Wedmann, Sonja, 2021, A Revision of fossil Bibionidae (Insecta: Diptera) from the Oligocene of Germany, Zootaxa 4909 (1), pp. 1-77 : 17

Penthetria nigra Statz, 1943 (figs. 11–12, 15, 95–99, 101)

Penthetria nigra Statz 1943: 38 .

Penthetria ♂ Nr. 1 Statz 1943: 41.

Localities: Rott, Enspel

Material examined: Holotype, female, LACMIP 2533.232 / LACMIP Type 3382 (part and counterpart, fig. 11). Likely male LACMIP 2533.246/LACMIP Type 3376 (fig. 12, = Penthetria sp. 1 sensu Statz).

Additional material, females: LACMIP 41997.111ab, GDKE PE 2015 5141; male: LACMIP 2533.1260ab; isolated wings: GDKE PE 1995 6383, PE 2016 5128. The specimen GDKE PE 2015 5141 includes one wing, thorax, parts of head including antenna, and femur and tibia of two detached legs, presumably mid- and hind leg. The abdomen is not preserved, but the head shows the specimen is a female. Given their size and width the isolated wings probably belong to female specimens.

Description:

Female (N=3, figs. 11, 95, 99):

Total length 10.3 mm (N=1). Brownish-black, probably entirely black in life.

Head: Length 1.1–1.5 mm (N=2). Black, rather small (partly covered by legs). Complex eye rounded, relatively small. Ocellar triangle quite small, not prominent. Antenna slender, flagellum 0.78–0.87 mm long, 0.17–0.18 mm wide (N=2), eight-segmented.

Thorax: Length 2.4 mm (N=1). Black, rather short, haltere black.

Legs: black, slender, hind tibia with fine, sharp spur. Fore femur 2.2 mm long, 0.41 mm wide, fore tibia 2.5 mm long, 0.24 mm wide, hind femur 2.9–3.0 mm long (N=2), 0.34 mm wide (N=2), hind tibia 3.3–3.4 mm long, 0.28–0.30 mm wide (N=2), hind first tarsomere 1.2 mm long, 0.19 mm wide.

Wing (fig. 95, 101): Lenght 9.8–10.5 mm, width 3.3–3.5 mm, length/width = 2.8–3.2 (N=4), blackish fumose, anterior third darkened. Pterostigma small, oval, blackish, not very prominent. Humeral vein present, fine. Subcosta straight , not very prominent. Costa extends to apex of R 4+5. R 2+3 long, horizontal, nearly straight, basally gently bent. R 4+5 gently, evenly curved. R-M vertical. Fork of M with short stem (beyond R-M). M-veins apically slightly curved basad. CuA-veins rather strong, CuA 2 apically bent basad. CuP close to CuA, straight, rather strong but does not reach wing margin. Vein measurements are given in Table 3 .

Abdomen (fig. 99): Length 6.1 mm, width 2.4 mm. Black, gently tapering. Cerci rather small.

Male (provisionally associated) (N=2, figs. 12, 96–98):

Total length 9.1–10.6 mm (N=2)

Head (fig. 97): Length 1.09–1.19 mm (N=2), width 0.95 mm (N=1), black, rounded, ocellar triangle prominent. Apparently dichoptic, with complex eyes above separated by a distance about equal to width of ocellar triangle (this is not entirely clear in the specimens at hand). Antenna slender, flagellum 0.56–0.57 mm long, 0.09–0.13 mm wide, cylindrical, 8-segmented, last segment conical. Palpus not visible in the specimens available.

Thorax: Length 2.3 mm (N=1). In dorsal view rather long and narrow (possibly a taphonomical artefact). Black, haltere brown.

Legs: Fore and mid femora pale with apical third black, hind femur pale with black tip, fore and mid tibiae and all tarsi black, hind tibia pale with black tip. Fore femur length 2.2–2.6 mm, width 0.32–0.40 mm, fore tibia length 2.6–2.8 mm, width 0.23 mm, fore first tarsomere length 1.0 mm, hind femur length 3.2 mm, width 0.45 mm (N=1), hind tibia length 2.5–3.2 mm, width 0.20–0.26 mm.

Wing (fig. 96): Length 6.6–8.8 mm, width 2.0– 2.7 mm, length/width = 3.3–3.4, blackish fumose, relatively narrow. Humeral vein present. Subcosta running close to R 1, obvious only apically. Pterostigma dark brown, rather broad. Costa extends a little beyond apex of R 4+5. R 2+3 long, horizontal, straight, basally gently curved. R 4+5 gently curved. R-M clearly oblique. M-veins fine, apically gently curved basad. CuA 1 rather straight, CuA 2 apically curved basad, CuP runs close to CuA, reaches wing margin. Vein measurements are given in Table 3.

Abdomen: Length 5.6–7.9 mm, width 1.0 mm (N=1), blackish-brown, slender.

Terminalia (fig. 98): Hypopygium width 0.73 mm (N=1). Gonostylus 0.32 mm long (N=1), robust, curved, apically pointed. Epandrium apparently dome-shaped.

Discussion:

The male appears to have a dichoptic head (as seen in specimen LACMIP 2533.1260), with complex eyes not meeting in frons. This trait would suggest placing the male specimens in genus Hesperinus . However, the short antenna and the straight R 4+5 point to the genus Penthetria . The recent species Penthetria funebris Meigen has a dichoptic head in the male, though in this case this trait is associated with brachyptery, whereas the Penthetria nigra male has normally developed wings. The specimens from Enspel are very fragmentary including one thorax, one partly preserved head, two legs and one partly preserved wing, in addition to two isolated wings. However, the characters that can be observed in these specimens do not differ appreciably from the Penthetria nigra specimens from Rott.