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The Genus Tachydromia Meigen (Diptera: Hybotidae) from the Afrotropics

ABSTRACT Two new species of the genus Tachydromia Meigen are described: T. freidbergi sp. n. (Ethiopia) and T. stuckenbergi sp. n. (Uganda). Re-descriptions of T. lilaniensis Smith, 1969 and T. petrabilis Smith, 1969, known from South Africa and Lesotho, are given. A key to Afrotropical Tachydromia is provided. Hypothesized phylogenetic relationships and the biogeography of Afrotropical species of Tachydromia are briefly discussed.


INTRODUCTION
The genus Tachydromia Meigen includes quite small (1.0 to 3.5 mm), ant-like flies usually with banded or maculated wings. It is represented in all biogeographic regions and currently comprises 118 species. However, only two species in this group are known from the Afrotropical region and these are described by Smith (1969) in his extensive monograph on Empididae from South Africa and Lesotho. In this paper we describe two new species from Ethiopia and Uganda. Additionally, we re-examine the type material of Smith's species of Tachydromia and give updated re-descriptions. This paper is the latest of several revisions covering the genus worldwide (Shamshev & Grootaert 2008;Grootaert & Shamshev 2009, in press;Shamshev & Grootaert 2009).
We dedicate one of the species (Tachydromia stuckenbergi sp. n.) described in this paper to the memory of Brian R. Stuckenberg. He did not work with empidoids but his collecting efforts greatly improved our knowledge of the Afrotropical representatives of these flies. Original descriptions of more than half of all the species of Hybotidae and Empididae known from this region are based on material collected by Stuckenberg. One genus (Stuckenbergomyia Smith, 1971) and one species (Acarterus stuckenbergi Sinclair, 1996) of Hybotidae, and two species of Empididae (Afroempis stuckenbergi Smith, 1969 and Edenophorus stuckenbergi Sinclair, 2002), have already been named after him.

MATERIAL AND METHODS
This study is based on material housed or deposited in the Natal Museum, Pietermaritzburg, South Africa (NMSA), the Royal Museum of Central Africa, Tervuren, Belgium (RMCA), the Royal Belgian Institute of Natural Sciences, Brussels (ISNB), Tel Aviv University, Israel (TAUI), the Canadian National Collection of Insects, Ottawa, Ontario, Canada (CNCI) and the Muséum National d'Histoire naturelle, Paris, France (MNHN). Pinned and alcohol-preserved specimens were examined, part of which was collected in Malaise traps. Terms used for adult structures primarily follow those of McAlpine (1981), although the terminology for the antenna and for the male terminalia follows Stuckenberg (1999) and Sinclair & Cumming (2006), respectively. To facilitate observations, the terminalia were macerated in cold 10% KOH and hot 85 % lactic acid and immersed in glycerine. Drawings of morphological features were made with a camera lucida attached to a compound microscope. In descriptions, the right and left side of the male terminalia are based on the unrotated position viewed posteriorly, such that in the illustrations the right surstylus appears on the reader's left side and vice versa. All male terminalia are figured in their unrotated position. TAXONOMY Genus Tachydromia Meigen, 1803 The species of the genus Tachydromia (= Sicus Latreille, 1796;Sicodus Rafinesque, 1815;Coryneta Meigen, 1800;Danistes Gistl, 1848;Phoneutisca Loew, 1863;Tachista Loew, 1864) can be diagnosed by the following combination of characters: eyes bare, dichoptic in both sexes, palpus usually narrow; thorax slender, largely shining, precoxal bridge present, postpronotal lobe large, thoracic setation usually greatly reduced; legs slender but fore femur often thickened, mid femur and tibia usually modified in male; wing with distinct anal lobe, usually brown banded, clouded or spotted, cell cup absent. The new species is dedicated to Dr Amnon Freidberg of Tel Aviv University (Israel), who collected it and many other interesting empidoids. Diagnosis: Recognised by a combination of the following characters: occiput largely shining; prothoracic sclerites shining; legs almost entirely blackish brown; wing with entirely separated bands; male mid femur with cluster of several short black ventral setae basally.
Wing: Normally developed, rounded at apex, with typical venation for the genus, with two broad brown bands, which are separated by narrow hyaline mid-stripe along the whole length. One moderately long costal bristle present. Vein R 2+3 slightly arched about middle toward costa. Veins R 4+5 and M 1+2 parallel toward wing apex. Cell r 1 very narrow, cells r 2+3 and r 4+5 of subequal width. Squama brownish coloured and fringed.
Haltere with whitish knob and brownish stem. Abdomen: Entirely blackish brown, shining, with scattered minute dark setulae; segments 1-7 unmodified. Distribution and seasonal occurrence: Currently this species is only known from two localities in Ethiopia. According to labels it was collected on Ethiopian Plateau (2000 m) in the middle of February and at the end of January. Remarks: The new species is similar to T. latifascipennis Brunetti, 1917 described from India (East Himalayas) and re-described by Chvála (1970). However, in T. latifascipennis the occiput is almost entirely densely grey-dusted and the mid femora of the male has a tuft of long yellow ventral hairs near the base. Additionally, T. freidbergi sp. n. can be distinguished from other African species using the characters given in the key.
Wing: Normally developed, rounded at apex, with unmodified venation; two broad brownish bands connected on cell r 1 . One short costal bristle present. Vein R 2+3 strongly arched about middle toward costa. Veins R 4+5 and M 1+2 parallel near wing apex. Vein CuM distinct throughout. Crossveins r-m and bm-cu broadly separated. Squama dusky yellow with concolorous fringe. Halter with pale knob and brownish yellow stem. Abdomen: Brownish, shining, covered with scattered black setae longer on pregenital segment; segments 1-7 unmodified. Terminalia small, rather elongate oval, blackish brown. We did not dissect the holotype male to examine the terminalia but Smith (1969: 73) indicates that they are very similar to T. lilaniensis. His fig. 82 is the right surstylus viewed from the inner side, which is subtriangular, with a deep notch on the lower (dorsal) margin, bearing several subapical spinules on inner side.

Female.
As in male, but mid tibia with hardly prominent subapical projection, cercus brownish, long, slender, covered with minute setulae. Distribution: South Africa, Lesotho. This species may have a wide distribution because, according to labels (Smith 1969), it was collected over a long period including September, January and April. The flies were taken on boulders near a stream edge. Remarks: Smith (1969) described this species after several specimens taken from three localities in the mountains of South Africa and Lesotho.
Diagnosis: Recognised by a combination of the following characters: eyes with upper hind corner extending beyond ocellar tubercle, vertex narrower than frons; thorax largely densely tomentose; wing almost uniformly brownish infuscate, narrowly pale basally. Description:

Male.
Length: Body about 3.3 mm, wing 2.4 mm. Head: Black. Eyes extending beyond ocellar tubercle and almost touching on vertex. Frons narrow, slightly widened toward ocellar tubercle, pollinose. Ocellar tubercle pollinose, ocellars minute. Occiput entirely pollinose, bearing 2 short closely set black verticals, 2 longer black setae on upper part laterally, covered with numerous whitish slightly flattened setae on lower part. Antenna with scape and pedicel yellow, pedicel and stylus missing. Proboscis brownish yellow. Palpus truncate, yellow, bearing several dark setulae near base and very long black subapical seta (missing). Thorax: Black, almost entirely tomentose, anepisternum (= mesopleuron), katepisternum (= sternopleuron) and meron (= hypopleuron) largely shining. Postpronotal lobe very large, lacking conspicuous setae. Mesonotum with 1 notopleural and 2 short closely set scutellars; acrostichals and dorsocentrals minute, the former arranged in 2 rows, lacking on prescutellar depression; the latter uniserial, 1 prescutellar pair somewhat longer. Legs: Long, slender, with complicated colour pattern; coxae and trochanters yellow, fore and mid femora brownish on subapical part (broader dorsally), hind femur almost entirely brownish (narrowly yellow basally), fore tibia with yellow dorsal face otherwise yellow, mid tibia entirely brown, hind tibia brown on about apical 1/3, fore and mid Tachydromia sp. Figs 9-11 In having wing bands joined along the costa (on cell r 1 ), brownish femora and tibiae and similar male terminalia (even the right surstylus with a notch), these specimens may belong to T. petrabilis. However, there are some differences in the length of the last dorsocentral and lateral scutal setae, and in the shape of the right surstylus. The true status of these specimens will be clear when additional material is available and the variability of these characters noted is understood. DISCUSSION Currently, the Afrotropical fauna of Tachydromia includes four species. This is the smallest number known from any biogeographic region, taking into account the recent contributions on the Oriental and Australasian representatives of the genus (Shamshev & Grootaert 2008;Grootaert & Shamshev 2009, in press;Shamshev & Grootaert 2009), and several species awaiting descriptions from Nearctic and Neotropical regions (Shamshev & Grootaert, in prep.). It is also surprising because, during this study, we examined rather extensive material from various areas of Africa, including that taken with masstrapping techniques over long periods. In these samples, Tachydromiinae (especially Platypalpus Macquart and Elaphropeza Macquart) were usually among the most abundant empidoids. It is interesting to note that no species of the genus Tachypeza (a sister group of Tachydromia) has been found yet in the Afrotropical Region.
Precise relationships of the Afrotropical species of Tachydromia will be discussed in a world fauna context of the genus. However, here we could note that T. freidbergi sp. n., T. lilaniensis and T. petrabilis are closely related on the basis of the very similar male terminalia, and show some affinity to the T. arrogans group (sensu Chvála 1970), which is represented by several species widely distributed in the Palaearctic Region, including Europe, Mediterranean, the Near East and Middle Asia. Tachydromia stuckenbergi sp. n. is a member of the T. luang group, sharing a similar structure of the head and male terminalia (Shamshev & Grootaert 2008).
Little is known about biology of Tachydromia in Africa. Smith (1969) noted label data indicating that the new species were observed running over large lichenous boulders. This habit is not very typical for Tachydromia, but it is known in several Palaearctic species. T. stuckenbergi sp. n. may belong to the canopy fauna. Additionally, all African species were collected in mountains on quite high altitudes (up to and over 2000 m). The few available records make it difficult to discuss biogeographic implications of the Afrotropical species of Tachydromia. That the species could have dispersed from the eastern Mediterranean southward through the Ethiopian Highlands and the Great Rift Valley to South Africa may be illustrated by T. freidbergi sp. n., T. lilaniensis and T. petrabilis (Fig. 8). There is evidence for such a route (Willassen & Cranston 1986;Kirk-Spriggs & Stuckenberg 2009), and there have been some examples suggested for empidoids (Chvála 1991;Sinclair 2003;Shamshev & Sinclair 2006). However, T. stuckenbergi sp. n. may represent another element of Tachydromia in the Afrotropical Region because its closest allies are known from the Oriental and Australasian Regions (most species) and from South America (one species).
(MNHN) for the loan of specimens used in this study. B. Sinclair kindly provided an Afrotropical map. Daniel Bickel (Sidney, Australia) and Igor Grichanov (St Petersburg, Russia) kindly provided useful suggestions on earlier drafts of the paper.