Penthetria graciliventris ( Théobald, 1937 ) Theobald, 1937

Skartveit, John & Nel, André, 2017, Revision of fossil Bibionidae (Insecta: Diptera) from French Oligocene deposits, Zootaxa 4225 (1), pp. 1-83 : 24-27

Penthetria graciliventris ( Théobald, 1937) comb.n.

(Figs. 10, 81–84)

Plecia graciliventris Théobald 1937: 138 .

Fig. 79 . Female, wing. NMB F1389/1.

Fig. 80 . Male, terminalia, dorsal. NMB F1399/1.

Fig. 82 . Female, wing. MNHN Monteils 25.

Fig. 83 . Male, terminalia, dorsal. MNHN Monteils 57. Fig. 84 . Male, head and thorax. MNHN Monteils 57.

The type of this species was said to be in Marseille, but we could not find it and it is possibly lost. However, some specimens from Monteils of a very distinctive, slender habitus fit perfectly Théobald (1937) ’s drawing (Pl. XI, Fig. 5) and description.

Material. 3 males (MNHN Monteils 35, Fig. 10, Monteils 55, Monteils 57.), 1 female: MNHN Monteils 25.

Localities. Célas, Monteils.

Diagnosis. A medium-sized species (8 – 9.5 mm) with an unusually slender habitus. The species is easily recognized by its very gracile body—the superficial habitus of a female of this species is more like a male of a typical bibionid, with a long, slender abdomen. The specimens at hand are of a uniform, brown colour. The strongly convex thorax gives this species a hunch-back appearance. Male gonostylus rather small, curved and pointed, epandrium small, subquadrate with a mesal indentation.

Redescription. Male. Total length 8.3 – 9.0 mm (N=3). Dark brown, likely black in life.

Head (fig. 84): Length 1.0 – 1.1 mm (N=3). Brown, rounded, compound eye rather small and rounded. Antenna rather short, flagellum possibly 7-segmented. Ocellar tubercle small.

Thorax: Length 2.0 – 2.1 mm (N=3). Short and strongly convex. Haltere light brown.

Wing (fig. 81): Length 6.1 – 6.9 mm (N=3), width 1.8 – 2.2 mm (N=3), length/width = 2.78 – 3.32 (N=3). Rather long and slender, light brown fumose, anterior area a little darker. Costa extends to nearly half-way between apices of R4+5 and M1. Humeral vein present, Subcosta relatively short, terminating mid-way between crossvein R-M and origin of R2+3. R-veins brown, posterior veins colourless. Pterostigma invisible. Vein R2+3 slightly sinuous, R4+5 distally distinctively curved. Basal part of Rs subparallel to M. Wing vein measurements in Table 1 .

Legs: Brown, slender. Fore femur 1.8 mm (N=1), fore tibia 1.9 mm (N=1), hind femur 2.3 – 2.8 mm (N=3), hind tibia 2.4 – 2.7 mm (N=2).

Abdomen: Length 6.6 – 6.8 mm (N=3). Long and narrow, cylindrical.

Terminalia (fig. 83): Epandrium quite small, suboval. Gonostyli relatively small, digitiform, curved and pointed.

Female: Total length 9.5 mm (N=1).

Head: Width 1.3 mm.

Thorax: Length 2.9 mm. Shape apparently as in male. Haltere pale brownish.

Wing (fig. 82): Length 7.8 mm, width 2.8 mm, length/width = 2.63. Light brown fumose, veins brown, pterostigma indistinctive. Costa extends to half-way between apices of R4+5 and M1. Humeral vein present, Subcosta relatively long. R2+3 nearly straight. Posterior veins fine, not possible to trace in specimen at hand.

Legs: Slender but not particularly long, femorae slightly clavate. Tibial spurs needle-thin. Fore femur 2.3 mm, fore tibia 2.1 mm, hind femur 2.5 mm, hind tibia 3.0 mm.

Abdomen: Length 7.2 mm, width 2.1 mm. Long and cylindrical, not apically tapered.

Terminalia: Abdominal tip rounded.

Figures

FIGURES 78 – 80. Penthetria gigantea (Théobald, 1937) Fig. 78. Male, wing. NMB F 1399 / 1.

FIGURES 81 – 84. Penthetria graciliventris (Théobald, 1937) Fig. 81. Male, wing. MNHN Monteils 57.