Plecia dubia ( Germar, 1837 ), 2021

Skartveit, John & Wedmann, Sonja, 2021, A Revision of fossil Bibionidae (Insecta: Diptera) from the Oligocene of Germany, Zootaxa 4909 (1), pp. 1-77 : 21-23

Plecia dubia ( Germar, 1837) (figs. 21–26, 108–113) Comb. n.

Phthiria dubia Germar, 1837

Helophilus primarius Germar, 1837 Syn.n.

Bibio dubius ( Germar, 1837) Giebel, 1856

Protomyia abava Heyden & Heyden, 1865: 20–21 . Syn.n.

Plecia abava (Heyden & Heyden) Statz 1943: 12 . Syn.n.

Plecia satyrus Statz, 1943: 12–13 . Syn.n.

Localities: Orsberg, Enspel, Rott

Material examined: Holotype (female) Phthiria dubia , STIPB A 595 (part and counterpart). Holotype (female) Helophilus primarius STIPB A 603. Syntype (male) Protomyia abava NHMUK In 58788, Syntype (female) Protomyia abava NHMUK In 58799. Syntypes Plecia satyrus LACMIP 2533 287 / LACMIP Type 3419, (female, part and counterpart), 2533.288 / LACMIP Type 3420 (female wing + abdomen, part and counterpart), 2533.289 / LACMIP Type 3421 (isolated wing), 2533.290 / LACMIP Type 3422 (isolated wing, part and counterpart).

Additional material (all in GDKE): Males: GDKE PE 1995 8363 (part and counterpart), GDKE PE 1995 8504 (part and counterpart, pyritised). Females: GDKE PE 1995 6310, PE 1997 5109, PE 1997 5738, PE 2008 5005, PE 2009 5980, LACMIP 2533.1087ab, 2533.1088ab. Isolated wings: GDKE PE 1995 6611, PE 1995 8265, LACMIP 2533.1279.

Description:

Female (N=14, figs. 21, 23–26, 108–109):

Entirely black, total length 13.3–15.5 mm (N=7)

Head: Length 1.4 – 1.9 mm (N=7), width 1.3 mm (N=3), relatively small. Ocellar tubercle not prominent. Antenna nearly as long as head, flagellum probably 9-segmented. Flagellum length 0.99–1.22 mm (N=4), width 0.19–0.25 mm (N=4).

Thorax: Length 3.3–4.3 mm (N=12), width 2.7–3.5 mm (N=5). Entirely black. Pile not apparent in specimens at hand. Haltere black.

Legs: Fore femur 2.6–3.3 mm long (N=3), 0.56–0.68 mm wide (N=3), fore tibia 3.1–3.6 mm long (N=2), 0.35 mm wide (N=1), hind femur 4.6–5.0 mm long (N=4), 0.67–0.83 mm wide (N=4), hind tibia 4.9–5.1 mm long (N=3), 0.42–0.48 mm wide (N=3), hind first tarsomere 1.4–1.6 mm long (N=2), 0.37 mm wide (N=1).

Wing (fig. 109): Length 10.9–14.3 mm (N=14), width 4.3–5.6 mm (N=13), length/width = 2.32–2.70 (N=13). Dark blackish fumose, costal cell darkened. Pterostigma indistinctive. R 2+3 medium-length, oblique, evently curved. Costa extends to apex of R 4+5, which is gently curved. Posterior veins weak, difficult to make out, CuA 2 apically rather strongly curved basad. Vein measurements are given in Table 4.

Abdomen: Length 8.0– 11.3 mm (N=9), width 3.2–4.2 mm (N=7). rather stout, cylindrical.

Male (N=3, figs. 22, 110–113):

Entirely brownish black. Total length 9.0–13.0 mm (N=2).

Head: (fig. 111) Length 1.5 mm (N=1), width 1.6 mm (N=1).

Thorax: Length 3.3–3.8 mm (N=3), width 3.0 mm (N=2).

Legs: Long and slender. Femora basally yellowish-brown, apically dark. Fore and mid tibiae and tarsi black, slender. Hind leg with tibia light brown, black-tipped, slender, spur fine and sharp. Fore femur 2.3 mm long, 0.52 mm wide (N=1), fore tibia 2.2–2.4 mm long (N=2), 0.25–0.28 mm wide (N=2), fore first tarsomere 0.94 mm long (N=1). Hind femur 3.8–4.1 mm long, 0.58–0.61 mm wide (N=2), thin in basal two thirds, apically clavate. Hind tibia 2.8–4.6 mm long (N=3), 0.61 mm wide (N=1). Hind first tarsomere 1.3 mm long, 0.42 mm wide (N=1), slightly swollen, spindle-shaped.

Wing (fig. 110): Length 9.4–10.3 mm, width 3.5–4.1 mm, length/width = 2.5–2.7 (N=2). Uniformly dark brownish fumose, veins dark brown, fine and fairly distinctive. Pterostigma indistinctive. R 2+3 oblique, relatively straight. R-M vertical, M with relatively long stem and short, rounded, symmetrical fork. CuA-veins apically straight. Vein measurements are given in Table 4.

Abdomen: Length 6.6–7.4 mm (N=3), width 1.8–2.0 mm (N=2). Rather slender, slightly conical.

Terminalia (figs. 112–113): Width of hypopygium 1.3 mm (N=2) Outline of hypopygium rectangular. Epandrium dome-shaped, apically rounded, strongly pilose. Gonostylus 0.51–0.68 mm long (N=3), straight, robust, moderately pilose, apically rounded. Last sternite dome-shaped with blunt, T-shaped mesal process.

Discussion: The senior name of this species was listed in the genus Bibio by Evenhuis (2014). The type of Helophilus primarius was originally interpreted as having paired spots on the abdomen, hence it was classified as a syrphid, though it obviously does not belong there ( Kotthoff & Schmid 2005). We cannot find any evidence of such spots, the wing venation is very similar to Phthiria dubia , which was originally placed in Bombyliidae . It seems a bit unclear if Helophilus primarius was formally published by Germar (1837), in the copy of his work which we have seen there is a plate of the specimen ( Germar 1837, Fasc. XIX Plate 25) but no printed description, just a handwritten diagnosis which may have been added at a later stage. In the material from Enspel there are several poorly preserved Plecia females which are substantially smaller than the well-preserved Plecia dubia specimens, suggesting the presence of a second species in the fauna. None of these specimens are well enough preserved to be identified at the species level, however. Statz (1943: 6) synonymised Plecia superba Meunier, 1915 with Plecia abava without having studied any specimens of P. abava . The wings of Plecia superba clearly differ from the type of Plecia abava and this synonymy is not valid in our opinion.