Bibio giganteus Unger, 1841

Skartveit, John & Krizmanić, Katarina, 2020, Revision of fossil Bibionidae (Insecta: Diptera) from the Miocene of Radoboj, Croatia, Zootaxa 4759 (3), pp. 351-378 : 364-367

Bibio giganteus Unger, 1841

( Figs. 12–14 , 32–33 )

Bibio giganteus Unger, 1841: 427 .

Syn. Bibio partschi Heer, 1849: 216 . Syn. n.

Syn. Bibio maculatus Heer 1849: 219 . Syn.n.

Penthetria Partschi (Heer) Pongracz, 1928: 172 . Type material: Holotype (female) of Bibio giganteus SLJG (77605). This is the specimen depicted by Heer (1849, Pl. XVI, Fig. 10 ). Syntype of Bibio maculatus SLJG 77474 . Holotype (female) of Bibio partschi NHMW (2007z013010001).

Additional material: Female ( SLJG 235), wing ( SLJG 35), wing and fragment of the rest of the specimen ( SLJG 13). Heer mentioned one specimen and three wings. Female ( NHMW D 1184), labeled as Bibio obsoletus . 3 females ( CNHM 1836, 1840, 1842). Female, probably non-type, NHMW 1852.1.1007 (labeled as Bibio partschi ).

Description

Female:Total length 12.5–17.7 mm (N=5).

Head: ( Fig. 33 ) Length 1.4 mm (N=1). Black. Poorly preserved in specimens at hand. Complex eye rather small, rounded. Ocellar tubercle small. Antennal flagellum apparently short and stout, 0.41 mm long by 0.19 mm wide, possibly five- or six-segmented.

Thorax: Length 3.9–4.6 mm (N=4), width 3.2–3.6 mm (N=3). Dark reddish brown. Halter reddish brown.

Wing ( Fig. 32 ): Length 10.0– 13.1 mm, width 3.7–4.4 mm (N=5). Brown fumose, costal cell conspicuously darkened, veins darkened, strong throughout. Pterostigma black, oval. Basal R s a little longer than R-M. Bm-Cu meets M 2 some distance beyond furcation of M. Veins M 1, M 2 and CuA 1 apically rather straight, CuA 2 a little curved. Vein measurements (all N=5): Subcosta 5.0– 6.8 mm, basal R 3.4–4.2 mm, distal R 1 2.6–3.3 mm, R s 1.0 – 1.6 mm, R 2–5 4.2–5.8 mm, R-M 0.4–0.6 mm., basal M 3.2–4.0 mm, distal M 0.8–1.4 mm, M 1 3.6–4.9 mm, M 2 3.2–3.9 mm, M-Cu 0.7–1.0 mm, CuA 2.0– 2.8 mm, CuA 1 5.0–6.0 mm, CuA 2 3.0–4.0 mm.

Legs: Dark brown, likely black in life. Protibia stout with a quite short spur. Length of fore tibia 2.8–2.9 mm (N=2), width 0.55–0.64 mm (N=2), length of hind tibia 4.2–4.7 mm (N=3).

Abdomen: Length 9.3–13.4 mm (N=5), width 3.3–4.3 mm (N=4). Tergites dark brown, pleura reddish brown. Cerci small and triangular.

Discussion: The nominal species Bibio giganteus , Bibio maculatus and Bibio partschi may appear distinctive since B. giganteus has conspicuously coloured wings, the others not. However, the morphometric traits of the wings are quite similar, and it seems most likely that the specimens classified as Bibio maculatus and Bibio partschi are Bibio giganteus specimens without preserved wing pigments. The similarity of B. giganteus and B. maculatus was noted already by Heer (1849: 219), who distinguished the two on the basis of B. giganteus having relatively longer abdomen (but the abdomen is notably swollen in the holotype of B. giganteus ) and B. maculatus having marginally narrower wings. Heer (1849: 216) distinguished Bibio partschi principally by its wider abdomen, this trait is, however, almost certainly an artefact of post-mortem swelling due to partial decay of the specimen before it was covered by sediment. The senior author has also seen material of this species from the late Oligocene site of Rott, Germany (Skartveit & Wedmann in prep.)

Figures

FIGURE 10. Bibio enterodelus, female, holotype of Bibio lividus, GBA 2009/016/0691.

FIGURE 12. Bibio giganteus, female, holotype, SLJG 77605.

FIGURE 13. Bibio giganteus, female, syntype of Bibio maculatus, SLJG 77476.

FIGURE 14. Bibio giganteus, female, holotype of Bibio partschi, NHMW 2007z013010001.

FIGURES 32–35. 32. Bibio giganteus, female, holotype, wing, SLJG 77605. 33. Bibio giganteus, female, holotype, head and thorax, SLJG 77605. 34. Dilophus pinguis, male, hind leg, CNHM 1832. 35. Dilophus pinguis, male, hypopygium, CNHM 1832. Scale bar = 1 mm.