A new species of Lygistorrhina Skuse (Diptera: Sciaroidea: Lygistorrhinidae) from South Africa

Abstract A new species of Lygistorrhina (Diptera, Sciaroidea, Lygistorrhinidae) from South Africa is described and a key for Afrotropical species of the genus is provided.


Introduction
Lygistorrhinidae is a small family of fungus gnats (Diptera, Sciaroidea) represented by 15 genera and 41 species (http://sciaroidea.info/taxonomy/41555). The genus Lygistorrhina includes 21 species which are distributed worldwide in tropical and warm temperate regions. Twelve species of the subgenus Lygistorrhina (L.) are known from the Old World (Africa, Eastern Palaearctic, South East Asia, Australasia and Oceania). In addition, an undescribed species of the subgenus was reported from Mexico (Huerta and Ibanez-Bernal 2008). Five Afrotropical species of Lygistorrhina (L.) were described from Kenya, Uganda, Côte d'Ivoire, Central African Republic, Gabon, Democratic Republic of Congo and Comoros (Matile 1978, Matile 1990, Matile 1996. In addition, an unnamed species is known from Madagascar (Matile 1996). In this paper we describe a new species of Lygistorrhina from South Africa in course of preparation of the chapter on Lygistorrhinidae for the Manual of Afrotropical Diptera.

Materials and methods
Descriptive terminology follows Söli 1997 andvein nomenclature Shcherbakov et al. 1995. Images of the pinned holotype were taken with an Olympus CP350 compact camera and eyepiece adapter on a stereomicroscope at the Hungarian Museum of Narural History, Budapest (HMNH). Paratypes were originally pinned; one of them was dissected, its wings mounted without media on a microscope slide, and the body was cleared in KOH and stored in glycerol. Details of the paratype were imaged in the Sackler Biodiversity Imaging Lab at the Natural History Museum, London by us of a Canon 450D camera attached to Zeiss Axioskop compound microscope. Additional images and materials are available at the Fungus Gnats Online web-site. All types are held in the HMNH.
Colouration. Body, head and antennae entirely dark brownish-grey, almost black, halters yellowish, legs yellowish-brown. Head ( Fig. 7) rounded, vertex slightly convex. Head dichoptic, oval. Ommatidia round, very densely set, equal in size. Interocular setae as long as the diameter of ommatidia. Three ocelli, almost in a straight line, equal in size, set each on its own mound, lateral facing to the sides, medial facing forward. Antenna (Fig. 4) with scape 1.3x shorter than wide, with ventral setae, pedicel spherical, with whorl of setae apically, flagellum 14segmented, moniliform, flagellomeres with length 1.5x the width, covered with setae 0.5x the width of flagellomeres, flagellomeres 1-11 with a few slightly longer dorsal setae. Bases of setae on flagellomeres form round depressions. Circular bases of flagellomere setae connected with folds forming polygonal pattern. Face as long as wide, with ventral and lateral setae. Clypeus rounded at apex, its length 1.5x the width. Palpi long, 0.6x the length of proboscis, tapering, with a single row of setae in apical 2/3. Proboscis evenly curved caudally, its length 2x the length of fore coxa. Lingua of hypopharynx very thin, transparent, tapering, with very thin hair at each side, longest at tip.
Thorax, legs, and abdomen uniformly dark brown (Fig. 1). Scutum (Fig. 2) evenly covered with setae of medium length, with longer supraalar setae. Scutellum short, without long setae. Postpronotum apparent, wide. Antepronotum and proepisternum both with 8 setae. Anterior margin of notum well anterior to fore coxa. Ventral margin of preepisternum 2 widely rounded. Metepisternal cleft deep, posterior margin of metepisternum longer than anterior, not extending the level of laterotergite. Laterotergite with a posterior row of 6 long setae. Mediotergite very convex. Wing (Fig. 3) hyaline, moderately wide, costal margin slightly convex. Microtrichia on membrane long (0.02 mm), overlapping. Costa with long setae, ending at 3/4 distance between R and M . Sc ending at C. R and R slightly sinusoid, setose dorsally and ventrally. Crossveins r-m and tb weak but distinct. M and M straight, the base of their fork is reduced, M begins more proximally than M . M and CuA evenly curved caudally, slightly diverging.  Legs (Fig. 5). Fore coxa is the longest, mid coxa a little shorter. Tibial and tarsal setae not in rows. Number of tibial spurs on fore, mid and hind tibia 1:2:2, fore tibia tibial spur short, ca. 1.5x the tibia diameter, mid and hind tibial spurs with inner spur longer, 1.7x and 1.4x the outer, respectively. Hind tibia expanded apically. Fore and mid tarsal claws blunt, curved, with a very small incision at apex and setiform curved basal process as long as the claw. Hind tibia claw pointed, almost straight, with shorter basal process.  Terminalia (Figs 6, 8). Tergite 9 (Figs 6c, d, 8) roughly arrow-shaped with rounded apex, length 0.17 mm, width 0.15 mm, with long scattered setae and a dense patch of short setae at apex. Apodeme of tergite 9 with short, narrow stalk, a little wider that ½ width of the tergite, with two strong semicircular anterior arms. Gonocoxites fused ventrally, with a deep incision, almost reaching the base of synsclerite (Fig. 6b). Synsclerite length 0.2 mm, width 0.26 mm. Gonostyli simple, length 0.13 mm, with a dorsoapical scoop-shaped tooth. Long flagellate setae on mediodorsal edge of gonostylus slightly shorter than gonostylus. Female. Unknown.

Diagnosis
The species differs from all Afrotropical species of Lygistorrhina in being smaller (wing length <2 mm), uniformly coloured very dark brownish-grey to black, and having shorter proboscis, which is at most 2x the length of coxa 1. Lygistorrhina austroafricana is most similar to L. edwardsina Grimaldi &Blagoderov, 2001 (Grimaldi andBlagoderov 2001), but differs in having a wider wing (length/width ratio 2.4 vs 2.7 in L. edwardsina) with shorter Sc (0.24x the wing length vs 0.33x) and shorter and wider tergite 9, with stronger anterior arms of apodeme. L. magna Matile, 1996(Matile 1996 also has a uniformly dark coloured body and wide apodeme of tergite 9, but it is a much larger fly (wing length 4.8 mm), and tergite 9 apodeme with stem wide and anterior arms not developed.

Etymology
The specific epithet is an adjective in reference to the place of origin of the specimens.

Distribution
South Africa: Eastern Cape.