Libanochlites neocomicus Brundin, 1976

Veltz, Isabelle, Azar, Dany & Nel, André, 2007, New chironomid flies in Early Cretaceous Lebanese amber (Diptera: Chironomidae), African Invertebrates 48 (1), pp. 169-191 : 182-183

Libanochlites neocomicus Brundin, 1976

Figs 13, 14

Description: Head 0.22 mm long. Ocelli absent.Antenna 0.5 mm long, more than twice as long as head, distinctly hairy, with 14 flagellomeres. Flagellomeres 1–13 covered with long setae (shortest 0.01 mm, longest 0.32 mm), scape broad and short, rounded, pedicel very short. Flagellomere 13 very long (0.07 mm); last 2 flagellomeres slightly more than half as long as remainder of flagellum. Flagellomere 14 long, tapering evenly/ consistently from base to apical nipple, less than half as long as flagellomere 13. Eye bare, with a distinct dorso-medial extension. Mouthparts lacking functional mandible; palps very short, with 4 visible palpomeres bearing numerous setae, all of similar length. Postocular, frontal, inner vertical and outer vertical setae not visible; possibly absent. Thorax 0.48 mm long, 0.25 mm wide, 0.27 mm high; postnotum with few setae, and no visible longitudinal median groove; scutellum with few posterior setae; scutum without median longitudinal groove; dorsal antepronotum with several setae.

Wing macropterous, 0.70 to 0.82 mm long, 0.22 mm wide, hyaline; membrane with setae. Radius with only 2 branches R 1 and R 4+5; R 1 short, 0.4 times as long as R 4+5. Costa with very long free end, distal of apex of R 4+5; cell between R 4+5 and costa narrow. Cross-vein MCu present, just proximal of RM; fork of Cu just proximal of MCu; Cu 1 not curved apically. Anal vein An 2 absent. Halter 0.1 mm long.

Fore femur length 0.44 mm, tibia 0.47 mm, tarsus 0.57 mm; mid femur 0.44 mm, tibia 0.5 mm, tarsus 0.73 mm; hind femur 0.44 mm, tibia 0.49 mm, tarsus 0.76 mm. All tarsomeres of fore, middle and hind legs cylindrical, not cordiform; first tarsomere of fore leg very long, but shorter than fore tibia. Mid and hind tibias with 2 spurs; claw of middle legs simple as in front and hind legs, not pectinate.

Abdomen 1 mm long, 0.07 mm wide.All tergites with 2 long dorsal setae; laterosternite IX fused with tergite IX. Gonostylus swollen at base and extended into a long, slender lobe with a sharp apical spine. Gonocoxite broad, with numerous long setae, elongate. Material examined: LEBANON: Mont Lebanon district [Mouhafazit Jabal Loubnan]: Specimens 236, 80, 179, 221, 250 A, 382, 940, 1148, 748 B (9ơ), 511, 537, 538, 781 A and B, 1111, 1272B (7^) and 723 G, H, I, J (1^, 3ơ) from Hammana/Mdeyrij, Caza Baabda (D. Azar coll.). South Lebanon district [Mouhafazit Loubnan el-Janoubi]: JG 375/3 BM 497, JG 375/5 BM 467 (2^), JG 375/1 BM 496 (ơ) from Jouar EsSouss (Jezzine outcrop) (Acra coll.). North Lebanon district: DAB 6 B (ơ) from El-Dabsheh (D.Azar coll.). Discussion: The male and female specimens examined have the same wing venation as the unique female holotype of L. neocomicus , from the outcrop of Jouar Es-Souss near Jezzine, usually known as Jezzine outcrop. The only differences are due to sexual dimorphism (number and structures of the antennomeres, size of the eyes, length of wings). Also the new male specimen (JG 375/1 BM 496) from Jezzine has the same genitalia as those from Hammana. Therefore, we consider that they belong to the same genus and species. The allocation of Libanochlites to the subfamily Podonominae was initially based on rather unimportant characters (Brundin 1976). However, the recent discovery of the male has allowed for a more detailed examination of the primary characters, which further supports the position of Libanochlites within the Podonominae .

Following the key to Holarctic subfamilies of Oliver and Dillon (1989), Libanochlites could fall within the Podonominae or the Buchonomyiinae . However, the laterosternite IX fused with tergite IX in Libanochlites is an apomorphy of the group Tanypodoinae and thus excludes affinities with the Buchomomyiinae ( Brundin & Saether 1978; Saether 2000 a). Despite having a wing venation very similar to that of Libanochlites , the Chilenomyiinae have distinctly different male genital structures (laterosternites IX, gonostyli) (Brundin 1983).

Within the Tanypodoinae, affinities with the Usambaromyiinae can be excluded because of the following characters: presence of vein MCu; tarsomere 4 elongate, not cordiform; claw of middle legs simple as in front and hind legs, not pectinate (Andersen & Saether 1994).Affinities with the Tanypodinae can be excluded because of the absence of vein R 2+3. Brundin (1976) indicated that this character is an apomorphy of the Podonominae , while the other character—an obsolete anal lobe—is also shared by Libanochlites . The Aphroteniinae , the last tanypodoine subfamily, can be excluded because within Libanochlites , vein MCu is retained; a character apomorphically absent in the Aphroteniinae . Libanochlites also has a narrow cell between R 4+5 and the costa, an apomorphy absent in the recent Aphroteniinae , but present in Podonominae ( Brundin 1966, 1976). The simple gonostylus of Libanochlites excludes affinities with the Podonomini and justifies allocation to the Boreochlini , after the female characters, already indicated by Brundin (1976). The most similar recent genus is Paraboreochlus Thienemann, 1939 , since cross-vein MCu is proximal to cross-vein RM, the pulvilli are not visible and thus probably absent, the tibial spurs are slender, and the eyes are bare ( Brundin 1966, 1976; Cranston et al. 2002). The broad gonocoxites and narrow elongate gonostyli of Libanochlites are also similar to those of this recent genus and yet very different from those of the other recent genera (Brundin 1989). Brundin (1976) separated Paraboreochlus from Libanochlites based on small differences in the wing venation. In Paraboreochlus , R 1 is comparatively longer, the wing itself is slightly longer, and the relative position of MCu with fork of Cu differs from Libanochlites . In addition, the male gonostylus of Paraboreochlus has small apical megaseta while in Libanochlites , the gonostylus has a sharp apical spine.

Figures

Figs 13, 14. Libanochlites neocomicus Brundin, 1976, male, specimen 723: (13) wing, scale bar = 0.3 mm; (14) genitalia, scale bar = 0.1 mm.