Plecia collossea ( Heyden & Heyden, 1865 )

Skartveit, John & Wedmann, Sonja, 2021, A Revision of fossil Bibionidae (Insecta: Diptera) from the Oligocene of Germany, Zootaxa 4909 (1), pp. 1-77 : 19-20

Plecia collossea ( Heyden & Heyden, 1865) (figs. 17–19, 103–107) Stat. Reinst.

Protomyia collossea Heyden & Heyden, 1865: 21 .

Plecia superba Meunier, 1915: 207–208 . Syn.n.

Plecia abava (Heyden) sensu Statz (1943: 12)

Plecia rhenana Heyden & Heyden sensu Statz (1943: 11)

Plecia imperialis Statz, 1943: 13, nec Schiner, 1868 Syn.n.

Plecia philippi Statz, 1943: 10–11 . Syn. n.

Plecia ♂ Nr. 1 Statz, 1943: 29.

Plecia ♂ Nr. 2 Statz 1943: 29–30.

Localities: Rott.

Material examined: Syntype (female) of Plecia collossea NHMUK In 58789 (fig. 17). Holotype (female) of Plecia imperialis LACMIP 2533.275/ LACMIP Type 3407. Holotype (female) of Plecia philippi LACMIP 2533.283 / LACMIP Type 3415.

Additional material: LACMIP 2533.257 LACMIP Type 3387 (male, = Plecia sp.1 Statz), LACMIP 2533.286ab/ LACMIP Type 3418 (female), LACMIP 2533.258/LACMIP Type 3388 (male, specimen illustrated by Statz 1943: Figs. 10 and 70), LACMIP 2533.1278ab (female), LACMIP 2533.1239, Siegburg Rott-787 (wings, presumably male).

Plecia superba Meunier, 1915 was described based on a single wing. We did not find the specimen in the Stadtmuseum Siegburg collection, however the original description of the species included a good photo of the specimen ( Meunier 1915, Pl. XXI, Fig. 2) which helped clarify the status of the species. Statz (1943: 6) corrected the length of the wing from 17 to 13.8 mm, this measure we used.

Description:

Female (N=11, figs. 17, 104–105):

Total length 13.3–17.8 mm (N=6).

Head: Length 1.3–1.7 mm (N=5), width 1.3–1.7 mm (N=4). Black. No details visible in type. In LACMIP 2533.1278 antenna rather short, cylindrical, flagellum 7- or 8-segmented, 0.94 mm long, 0.21 mm wide (N=1). Complex eye rather large, not protruding.

Thorax: Length 3.4–4.8 mm (N=5), width 3.0– 3.8 mm (N=3). Black. Haltere brownish-black.

Legs: tibiae pale brownish with black tip, tibiae pale brownish basally, dark in apical third, slender. Hind tibia with small, sharp, curved spur. Tarsi black, slender. Length of fore tibia 3.0– 3.6 mm (N=3), hind femur 4.0– 4.3 mm (N=2), hind tibia 4.0– 5.2 mm (N=4).

Wing (fig. 105): Length 12.0– 14.6 mm (N=12), width 4.1–5.5 mm (N=11), length/width = 2.5–2.9 (N=11), dark brownish-black fumose, costal cell darkened. Humeral vein present, oblique. Pterostigma brown and indistinctive to quite invisible. Costal cell rather wide. Subcosta straight, fine. Costa extends some distance beyond apex of R 4+5. R 2+3 medium-length, oblique, gently and evenly curved. R 4+5 rather straight. R-M vertical. M-veins apically almost straight. CuA-veins strong, apically curved basad. Vein measurements are given in Table 4.

Abdomen: Blackish-brown, rather stout, apically rounded. With abundant, fine, dark pile (LACMIP 2533.1278). Cerci do not protrude from abdominal tip.

Male (N=4, figs. 18–19, 105–107):

Total length 14.0– 16.5 mm (N=2)

Head (fig. 106): Length 1.8–2.0 mm, width 1.9–2.0 mm (N=2). Oval, blackish-brown. Complex eye dichoptic, moderately large, not at all protruding, a little more than half length of head. Antenna robust, flagellum 8-segmented. Palpus brown, robust.

Thorax: Length 3.9–4.1 mm (N=3), width 2.9–3.4 mm (N=2). Blackish-brown, haltere pale brownish.

Legs: Femora moderately thickened, tibiae and tarsi slender. All femora pale yellowish with brown tips. Fore tibia pale yellowish, distal third brown. Mid tibia pale yellowish, distal fourth brown. Hind tibia pale yellowish with dark brown tip. All tarsi brownish, first hind tarsomere basally pale. The legs are covered with fine, short, brown pile.

Wing (fig. 107): Length 11.7–12.5 mm (N=4), width 4.0 mm (N=3), length/width = 2.9–3.1 (N=3). Hyaline or slightly brownish fumose, costal cell heavily darkened but with a clear stripe between Subcosta and R 1, the area distal to R 2+3 is also lighter. Pterostigma oval, dark brown, indistinctive due to the wing’s general dark colour. Humeral vein present and relatively strong, oblique. Subcosta straight, basally very strong but tapering distally, running well clear of R. Costa extends to 0.4 times distance between apices of R 4+5 and M 1. R 2+3 medium-length, oblique, evenly curved. R 4+5 apically moderately curved. R-M vertical. Fork of M asymmetrical, M 2 is almost straight while M 1 is distinctly curved. CuA 1 almost straight, CuA 2 distally curved basad. A pseudovein runs parallel to CuA. CuP straight, fine. A 1 distinctive on wing stem, straight. Vein measurements are given in Table 4.

Abdomen: Length 9.2–12.1 mm (N=2), width 2.3–2.9 mm (N=3). Black, rather long and narrow, cylindrical, densely clad with short, dark pile. Abdominal tip rounded, terminalia not well preserved.

Discussion: The species was synonymised with Plecia morio ( Heer, 1849) by Skartveit & Nel (2017) but, having examined additional material we no longer believe these names are synonymous, hence Plecia collossea is reinstated as a valid species.