New species of Metachela Coquillett (Diptera, Empididae) from the Atlantic Forest, Brazil and a key to the Neotropical species

Abstract Two new species of Metachela Coquillett from the Brazilian Atlantic Forest, M. danitakiyae sp. n. from Rio de Janeiro and Minas Gerais and M. spinulosa sp. n. from Minas Gerais, are described and illustrated. A key to the Neotropical species is provided.


Introduction
Metachela Coquillett [type species M. collusor (Melander)] is part of the tribe Hemerodromiini, and contains 12 previously described species, plus two species described here (see Table 1) with representatives in Western Europe, and the Neotropical and Nearctic regions (Yang et al. 2007). However, specimens of the genus are also known from Australia (pers. obs.). Collin (1933) and Smith (1962) described some South American species of Metachela, but considered them to be atypical in terms of antennal characters, thoracic shape, and head setation. MacDonald (1989) revised the genus; however, he covered only the three North American species. Yang et al. (2007) catalogued only eight species of Metachela for the Neotropical Realm; however, more species still await description as Cumming and Sinclair (2009) mention an undescribed species from Costa Rica. There are two species recorded for Brazil: M. barueri Smith from São Paulo and M. breviradius Smith from Santa Catarina (Smith 1962). The remaining Neotropical species were described from the extreme south of South America, in southern Argentina and southern Chile (Collin 1933). Herein, two new species are described from southeastern Brazil, and a key to the Neotropical species is provided.

Materials and methods
This study is based on the examination of specimens housed at Instituto Nacional de Pesquisas da Amazônia, Manaus, Amazonas, Brazil (INPA). Species with long series of representatives will also be deposited in the Museu Nacional do Rio de Janeiro (MNRJ), and Museu de Zoologia da Universidade de São Paulo (MZUSP). The specimens were collected using Malaise traps placed over small streams.
Dissected structures were macerated in heated 85% lactic acid (Cumming 1992) and examined on excavated slides. Wings were mounted on microslides, terminalia were placed in microvials with glycerin, and these were pinned with their associated specimens. Terminology follows .
The holotype label data was cited in full before the description, with original spelling and punctuation. Data from each label was enclosed by quotation marks (" "). Information presented within square brackets ([ ]) is supplementary data not present on the labels.  (Walker, 1849) x Canada and USA M. barueri Smith, 1962 x x Brazil (São Paulo) M. breviradius Smith, 1962 x Brazil (Santa Catarina) M. circumdata Collin, 1933 x x Argentina (Bariloche) M. collusor (Melander, 1902) x x Canada and USA M. convexa MacDonald, 1989 x USA (California) M. danitakiyae sp. n.
x x Brazil (Rio de Janeiro, Minas Gerais) M. flavella Collin, 1933 x Chile (Casa Pangue) M. hexachaeta Collin, 1933 x x Chile (Casa Pangue, Puerto Varas, Puerto Montt, Peulla) M. inornata Collin, 1933 x Argentina (Bariloche) M. instabilis Collin, 1933 x Chile (Puerto Varas) M. nigriventris (Loew, 1864) x x Austria, Germany, Hungary, Italy? M. patula Collin, 1933 x Diagnosis. Face with some pale setae, front tibiae with apical rather trowel-like projection beneath and no spine, crossvein h present, cells bm and dm fused (crossvein bm-cu absent), M 1 and M 2 with common petiole arising from anterior end of crossvein dm-cu and cell CuP present. The Neotropical Metachela differs from the typical northern species by lacking a distinct stylus, having the thorax more pointed anteriorly, possessing four to equally spaced vertical setae and lacking spine below the front tibia.

Key to the Neotropical species of Metachela
Male (Fig. 1). Head (Fig. 1): Dark brown to black, setae whitish. Ocellar triangle with two pairs of proclinate bristles, anterior pair stouter. Eyes iridescent black, separated on face. Occiput with scattered fine setae. Mouth parts yellow; proboscis short, slightly curved and with yellow setae. Antenna yellow, with scape and pedicel bearing distinct short ventral setulae; postpedicel nearly 2× as long as wide; stylus very short, ~ 0.1× as long as postpedicel.
Thorax (Fig. 1): Elongate, slightly arched dorsally; scutum yellowish except for midlongitudinal brown stripe, wider posteriorly, and brownish posterolateral spot above wing base; scutum with very small and fine yellow setae except for one notopleural, one postalar, and two pairs of small parallel scutellars; scutellum and mediotergite brown.  Legs ( Fig. 1): Yellow, except fore tibia with narrow anteroventral brown stripe distally, and hind femur at distal 2/3 and tarsomeres 4-5 brown. Fore coxa as long as distance between fore-and mid coxae, 4× as long as wide, with some dorso-apical pale setae. Fore femur approximately 1.3× as long as fore coxa, 4.5× as long as wide, with anteroventral row of 3-5 spines, anteroventral row of 6-8 denticles, and posteroventral row of 18-20 denticles, with basal ones stouter; anteroventral row of denticles placed on distal half and posteroventral row restricted to distal 0.9, and both rows without apical discontinuity and diverging at apex. Fore tibia approximately 0.8× as long as fore femur; with decumbent short pale bristles dorsally, more densely distributed apically. Mid femur with two anteroventral and 12 posteroventral spines, basal pair stouter. Hind legs slender, with fine setae, except hind tibia with dorsoapical comb of short setae.
Geographical records. Brazil (Minas Gerais and Rio de Janeiro states). Etymology. The specific epithet is a tribute to Daniela Maeda Takiya, friend of the authors and collector of the specimens.
Remarks. Metachela danitakiyae sp. n. differs from other species by the elongate male cercus, narrower on the apical 1/4 (usually short in other species, if elongate then with broad apex); epandrium with a posterodorsal sinus (without sinus in other species). Diagnosis. Scutum with a mid-longitudinal brown stripe; vein R 2+3 fused to R 1 ; male cercus with truncate apex and somewhat scattered spine-like setae; epandrium with an apicoventral acute projection; female tergite 8 with bilobate apex; female tergite 10 divided into two sclerotized plates separated by a membranous area.
Thorax (Fig. 12): Elongate, slightly arched dorsally; scutum yellowish except for mid-longitudinal brown stripe, darker posteriorly, and brownish posterolateral spot above wing base; scutum with very small and fine yellow setae except for one notopleural, one postalar, and two pairs of small parallel scutellars; scutellum and mediotergite brown; Legs (Fig. 12): Yellow. Fore coxa as long as distance between fore-and mid coxae, 3× as long as wide, with some dorsoapical pale setae. Fore femur (Fig. 13) 1.2× as long as fore coxa, 3.5× as long as wide, with anteroventral row offour spines, anteroventral row of 4 denticles, and posteroventral row of 17 denticles, with basal one stouter; anteroventral row of denticles placed on distal half and posteroventral row restricted to distal 0.9, and both rows without apical discontinuity and diverging at apex. Fore tibia (Fig. 14) ~ 0.8× as long as fore femur; with decumbent short pale setulae dorsally, denser apically. Mid femur with 2 anteroventral and 15 posteroventral spines, basal pair stouter. Hind legs slender with fine setae, except hind tibia with dorsoapical 'comb' of short setae.
Geographical records. Brazil (Minas Gerais). Etymology. From the Latin spinosus (spine), referring to the spine-like setae on the male cercus.
Remarks. Metachela spinulosa sp. n. differs from other species especially by the male cercus with scattered spine-like setae (absent in other species) and epandrium with an apicoventral acute projection (absent in other species).

Discussion
The Atlantic forest is one of the five most important biodiversity hotspots in the world (Myers et al. 2000). In face of the rapid anthropic changes to this area, it is important that its fauna be studied, including Diptera, before of it is lost. Prior to the current study, there were only two species of Metachela described from this biome, and no doubt there are certainly new species still left to be described.