Hesperinus heeri ( Heyden & Heyden, 1865 ), 2021

Skartveit, John & Wedmann, Sonja, 2021, A Revision of fossil Bibionidae (Insecta: Diptera) from the Oligocene of Germany, Zootaxa 4909 (1), pp. 1-77 : 12-14

Hesperinus heeri ( Heyden & Heyden, 1865) (figs. 1–5, 85–90) Comb.n.

Protomyia heeri Heyden & Heyden, 1865: 28

Plecia elegantula Meunier, 1915: 226 . Syn.n.

Penthetria rottensis Statz 1943: 40 . Syn.n.

Penthetria scita Statz 1943: 40–41 . Syn.n.

Plecia ♂ Nr. 8 Statz 1943: 33.

Plecia heeri ( Heyden & Heyden, 1865) Statz 1943: 5 .

Localities: Rott

Material examined: Holotype Protomyia heeri (male) NHMUK In 58817 (fig. 3). Holotype Penthetria rottensis (female, part and counterpart), LACMIP 2533.233/LACMIP Type 3383 (fig. 1). Holotype Penthetria scita (female, part and counterpart), LACMIP 2533.234/LACMIP Type 3384 (fig. 2). We did not find the type of Plecia elegantula Meunier (= Plecia ♂ Nr. 8 Statz 1943) in Stadtmuseum Siegburg, however a good photograph of the specimen was published ( Meunier 1915 Plate 26). According to Statz (1943: 33) his Plecia ♂ Nr. 8 is the same as Plecia elegantula Meunier.

Additional material, males LACMIP 2533.264/LACMIP Type 3394, 41997.101ab, STIPB A-544, A-564, Siegburg Rott 594 (part and counterpart).

Description:

Female (N=2, figs. 1–2, 85–86):

Head: width 1.2 mm, very poorly preserved in type of P. rottensis , missing in type of P. scita .

Thorax: Length 2.0– 2.2 mm (N=2). Blackish-brown, rather short, haltere light brown.

Legs: Only parts of front leg preserved in type of P. rottensis , missing in type of P. scita . Apparently, the femur is brownish-yellow and the tibia brown.

Wing (figs. 85–86): Length 6.0– 7.5 mm, width 2.1–2.6 mm, length/width = 2.8–2.9 (N=2). Rather narrow, apically rounded, light brownish fumose, veins brown. Radial veins strong, posterior veins fine. Pterostigma oval, brown, fairly distinctive. Humeral vein present. Subcosta long, running close to R 1, not very distinctive. Costa extends some distance beyond apex of R 4+5. R 2+3 of medium length, oblique, gently curved. R 4+5 rather strongly curved apically. R-M vertical. M-veins gently curved. CuA-veins strong, CuA 2 apically curved basad. CuP straight, reaches wing margin, A 1 visible basally only. Vein measurements are given in Table 2.

Abdomen: Length 5.7–6.3 mm, width 1.6–1.7 mm, brown, conical. Cerci two-segmented, rather long, slender. Three spermathecae are visible.

Male (N=7, figs. 3–5, 87–90):

Total length 7.1–10.0 mm (N=4)

Head: Length 0.9–1.1 mm (N=3), width 1.3 mm (N=2), Brown. Dichoptic as usual for genus. Rostrum somewhat elongated. Ocellar triangle small but distinctive. Palpus rather long and slender. Antenna not well preserved, but in one specimen (LACMIP 41997.101ab) the flagellum seems to be about 0.85 mm long and 0.07 mm wide (exact length uncertain), making it considerably more slender than in other fossil bibionids from Germany.

Thorax: Length 1.9–2.5 mm, width 1.7–2.2 mm (N=5). Mesonotum pale brownish, likely much darker in life, pleurae dark brown. No traces of pile preserved. Haltere light brown.

Legs: relatively long and slender. Femora pale with brown tips, tibiae and tarsi brown. Length of fore femur 1.9–2.7 mm (N=2), width 0.33 mm (N=1), fore tibia length 2.6 mm, width 0.19 mm (N=1), hind femur length 2.5–3.4 (N=3), hind tibia length 2.6–3.4 mm (N=4), width 0.24 mm (N=2), hind first tarsomere length 1.0– 1.2 mm (N=2). Tibiae and tarsi quite slender.

Wing (fig. 88): Narrow, apically rounded, light brownish fumose, veins fine and brown throughout. Length 5.5–7.5 mm (N=5), width 1.6–2.4 mm (N=5), length/width = 3.0–3.4 (N=5). Humeral vein present, oblique, subcosta fine, straight, not very long. Pterostigma invisible. Rs branches off from R at about 0.4 times the wing length, rather short. R-M vertical. R 2+3 oblique, straight, of medium length. R 4+5 apically strongly curved, at tip nearly parallel to Costa. Fork of M rather narrow, asymmetrical with M 1 diverging forward from M/M 2. Both M 1 and M 2 apically distinctively curved basad. Crossvein M-Cu situated near basis of CuA 1. Fork of CuA quite narrow. Vein measurements are given in Table 2.

Abdomen (fig. 90): Length 5.7–6.8 mm (N=3), width 1.2–1.5 mm (N=2), light brown (may have been darker in life), rather long and slender, conical.

Terminalia (fig. 89): Last abdominal segment dark brown, notably darker than rest of abdomen (likely as a consequence of being heavier sclerotised?). Hypopygium 0.78–0.90 mm wide (N=5). Gonostylus 0.37–0.46 mm long (N=2), robust, curved, blunt.

Discussion: The genus Hesperinus is generally characterised by the small, dichoptic male head and the elongate antenna (Krivosheina 1997). The recent species of the genus have very slender bodies but this is less obvious in some fossil species placed in the genus ( Skartveit 2009). None of the specimens from Rott have well-preserved heads, however the head in the male specimens appears to be dichoptic, strongly suggesting an affinity with Hesperinus . In addition, these specimens have relatively narrow wings with strongly curved R 4+5, and pointed, conical abdomens, about 3 times as long as the thorax, which also suggest the genus Hesperinus . This falls short of being conclusive evidence, but we consider it more likely that the species belongs in Hesperinus than in Penthetria .

Genus Penthetria Meigen, 1803