Bibio castaneipennis, Skartveit & Wedmann, 2021

Skartveit, John & Wedmann, Sonja, 2021, A Revision of fossil Bibionidae (Insecta: Diptera) from the Oligocene of Germany, Zootaxa 4909 (1), pp. 1-77 : 43-44

Bibio castaneipennis sp.n. (figs. 68–69, 181–189)

Localities: Enspel

Material examined: Holotype (male) GDKE PE 1997 5697 (fig. 68). Paratypes (males) GDKE PE 2010 5377, GDKE PE 2014 5307, GDKE PE 2014 5423 (females) GDKE PE 1995 5212 (fig. 69), GDKE PE 1995 5252, GDKE PE 1995 5397, GDKE PE 1995 5410, GDKE PE 1995 5585, GDKE PE 1995 7228

Additional material (all in GDKE): Males: PE 2012 5237. Females: PE 1995 5098, PE 1995 5153, PE 1995 5189, PE 1995 5253, PE 1995 5279, PE 1995 5310, PE 1995 5393, PE 1995 5647, PE 1995 6009, PE 1995 6170, PE 1995 6272, PE 1995 6309, PE 1995 6361, PE 1995 6701, PE 1995 6884, PE 1995 7159, PE 1995 7227, PE 1995 7319, PE 1995 7866, PE 1995 8335, PE 1995 8369, PE 1995 8572, PE 1995 8970, PE 1995 8997, PE 1995 9114, PE 1995 9143, PE 1995 9268, PE 1995 9279, PE 1995 9396, PE 1995 9418, PE 1995 9452, PE 1995 9458, PE 1995 9469, PE 1995 9600, PE 1995 9618, PE 1997 5342, PE 1997 5352, PE 1997 5879, PE 1997 6152, PE 2009 5957, PE 2010 5359, PE 2010 5393, PE 2010 5451, PE 2010 5474, PE 2010 5513, PE 2010 5536, PE 2010 5606, PE 2010 5800, PE 2010 5900, PE 2012 5022, PE 2012 5063, PE 2012 5082, PE 2012 5179, PE 2012 5205, PE 2012 5362, PE 2012 5365, PE 2012 5374, PE 2012 5394, PE 2012 5413, PE 2013 5003, PE 2013 5066, PE 2014 5195, PE 2015 5014, PE 2015 5119, PE 2015 5227, PE 2017 5055.

Etymology:

from Latin castanea, chestnut and penna, feather. The species has conspicuously dark, chestnut-brown wings and is named accordingly.

Diagnosis:

A relatively large Bibio ¸with wing length 8.4–12.5 mm. Antennal flagellum slender, 8–9-segmented. Fore tibia with spur about half as long as spine. Wing blackish-brown fumose, in female but not in male with conspicuously strong venation. Crossvein R-M about one-half the length of basal Radial sector. Male epandrium with two rounded lobes separated by a V-shaped cleft, gonostyli robust.

Description:

Female (N=51, figs. 69, 181–183):

Length 9.0– 18.5 mm (N=51). Body uniformly dark brown in pigmented specimens.

Head: Length 1.15–2.11 mm (N=32), width 1.05–1.85 mm (N=8). Complex eye moderately large, occupying about two thirds of head length laterally, rather flat. Antennal flagellum slender, 8–9-segmented. Ocellar triangle rather low, not prominent. Last palpus segment cylindrical.

Thorax: Length 2.6–5.1 mm (N=46), width 2.4–3.4 mm (N=7) Brownish-black, mesonotum relatively flat, scutellum not prominent. Haltere blackish-brown. Pile not preserved.

Wing (fig. 183): Length 8.8–12.6 mm (N=40), width 3.0– 5.3 mm (N=35), length/width = 2.33–2.96 (N=35). Dark brown fumose, costal cell notably darkened. Veins strong and distinctive, dark brown. Pterostigma oval, rather small, not notably darker than membrane (visible in pyritised specimens only). Venation as in male. Vein measurements are given in Table 5.

Legs: Fore femur length 1.8–3.0 mm (N=11), width 0.60–0.89 mm (N=7). Fore tibia length 1.7–3.2 mm (N=16). Hind femur length 2.8–4.8 mm (N=15), width 0.55–0.84 mm (N=11). Dark brown. Hind femur moderatly clavate, hind tibia robust but not swollen, with short, dark pile, hind tarsus robust. Hind tibial spur slender, straight, about one third as long as first tarsomere.

Abdomen: Length 5.3–12.5 mm (N=39), width 1.8–4.4 mm (N=14) Somewhat spindle-shaped, relatively long, apically truncate. Cerci moderately large, rounded.

Male (N=15, figs. 68, 184–189):

Total length 9.0–16.0 mm (N=15, some specimens with contracted abdomen). The pigmented parts of the specimens are uniformly dark brown. 5 of the 15 specimens at hand are partly or entirely pyritised.

Head (fig. 187): Lenght 1.3–2.4 mm (N=13), width 1.3–1.9 mm (N=4). Ocellar tubercle moderately well developed. Intraocular pile not preserved in the specimens at hand. Antennal flagellum slender, 0.65–0.82 mm long (N=4), probably 8–9-segmented. Palpus a little longer than antenna, last segment cylindrical.

Thorax (figs. 184, 185): Lenght 3.0– 4.8 mm (N=14), width 2.4–3.4 mm (N=3). Brownish-black, mesonotum moderatly convex. Scutellum rather small, not prominent. Haltere yellowish-brown. Pile not preserved.

Wing (fig. 186): Length 8.4–11.3 mm (N=8), width 3.0– 4.3 mm (N=7), length/width = 2.4–2.8 (N=6). Brown fumose, costal cell a little darkened, veins not particularly strong, brown throughout. Pterostigma not notably darker than membrane. Costa extends to apex of R 4+5. Humeral vein present, oblique. Subcosta indistinctive. Basal Radial sector about twice as long as crossvein R-M. Vein M with fork about twice as long as stem. Crossvein M-Cu reaches M 2 a little distal of furcation. CuA-veins strong, CuA 2 apically a little bent basad. Vein measurements are given in Table 5 .

Legs: Femora brown, tibiae and tarsi blackish-brown. Fore femur moderatly thickened, length 1.9–3.4 mm (N=9), width 0.56–0.95 mm (N=7). Fore tibia length 1.7–3.3 mm (N=4). Spur about half as long as spine. Hind femur clavate, basally slender, length 3.4–5.2 mm (N=10), width 0.58–0.92 mm (N=9). Hind tibia straight, apically truncate, relatively slender, length 3.4–5.2 mm (N=7), width 0.42–0.78 mm (N=7). Tibial spur rather short, first hind tarsomere moderately thickened.

Abdomen: Length 6.0– 10.3 mm (N=14), width 1.9–3.0 mm (N=6).

Terminalia (figs. 188, 189): Width 1.2–1.7 mm (N=8). Epandrium with two rounded lobes separated by wide, Vshaped cleft. Gonosylus robust, apically hooked.

Discussion:

This morphospecies displays a wide range in size, but this is to be expected in a large material of Bibionidae . We have not found any consistent, morphological differences between specimens in the small and large end of the size range. There is some variation in the apparent pigmentation of the wings, but this is probably of taphonomical origin as the venation seems very similar. Among the> 1000 bibionid specimens from Enspel in GDKE seen by the first author, this species probably makes up about 90%.