Chersodromia dominicana, Solórzano Kraemer & Sinclair & Cumming, 2005

Solórzano Kraemer, Mónica M., Sinclair, Bradley J. & Cumming, Jeffrey M., 2005, Five new species of Tachydromiinae (Diptera: Empididae s. l.) from New World Tertiary ambers, Zootaxa 1010, pp. 37-52 : 42-45

Chersodromia dominicana sp. nov.

Stilpon sp. Cumming & Cooper 1992: 956

Stilpon unidentified sp.: Evenhuis 1994: 355 DIAGNOSIS. Distinguished from other species of Chersodromia by cell br and bm being relatively short with cell br slightly shorter than cell bm (rather than the same length or longer) ( Fig. 2C).

DESCRIPTION. Male ( Fig. 2A). Length 1.1 mm. Head. ( Fig. 2B) Ground colour brown. Eyes apparently lacking ommatrichia (pubescence); widely separated below antennae; facets not noticeably enlarged below antennae. Face flat, parallel­sided, nearly as broad as bases of antennae; entirely tomentose. Frons parallel­sided; broad, wider than width of ocellar triangle. Two pairs of ocellar bristles; anterior pair convergent, inserted lateral to median ocellus and broadly separated; posterior pair inserted posterior to median ocellus and interval at base subequal to diameter of median ocellus. One pair of convergent vertical bristles. Antennae arising near middle of head; scape small, shorter than half length of pedicel; pedicel large globose, with long ventral preapical bristle; postpedicel small, ovate, with dorsoapical extension; arista­like style arising dorsoapically from extension of postpedicel; style longer than thorax; basal antennal segments yellow, postpedicel and style dark brown. Palpus elongate­ovate with long, distinct apical setulae.

Thorax. Ground colour dark. Postpronotal lobe small, with 2 pprn; acr biserial; 2 npl; dc biserial; 2 spal; 1 pal; 1 subapical pair sctl, less than one­half length of apical sctl; 1 apical pair sctl long and slightly convergent. Tomentum pattern of scutum not visible.

Wing. ( Fig. 2C) Length 0.9 mm. Broad with blunt­tip; hyaline; microtrichia evenly distributed; costal setulae well developed; R 2+3 extending to apical third of wing; R 4+5 parallel to M 1+2, only slightly curved toward costa; cells br and bm relatively short with cell br only slightly shorter than cell bm; crossvein bm­cu nearly transverse; A 1 absent. Knob of halter dark.

Legs. Fore femur moderately thickened with row of outstanding posteroventral bristles; fore tibia with prominent preapical ventral bristle. Mid femur more slender than foreleg, with 3–4 prominent preapical bristles surrounding apex; mid tibia with anterior bristle on apical third. Hind femur slightly bent near base, with row of short anteroventral bristles; 3–4 preapical bristles surrounding apex. Hind tibia with 2 anteroventral bristles on either side of mid­length; 2 anterodorsal bristles on apical half; 1 dorsal bristle near midlength.

Abdomen. ( Figs. 2D–E) Segments uniformly telescopic, lacking distinctive bristles. Terminalia: Hypandrium fused with left epandrial lamella. Left cercus longer than right, digitiform with long bristles. Left surstylus with short processes and large subtriangular lobe. Right surstylus comprising 3 lobes: uppermost flattened, slightly twisted; middle lobe strongly bent at mid­length, tapered apically to narrow point; lower lobe flattened with truncate apex.

TYPE. Holotype male from Dominican Republic: exact locality unknown, found in jewelry pendent. Deposited in CNC. The holotype is in excellent condition, in a somewhat cube piece of clear amber measuring about 4.5 x 2.3 mm.

REMARKS. The inclusion represents the first fossil species of Chersodromia to be described. Almost all extant species of Chersodromia are found on coastal beach habitats ( Chvála 1978).

Cumming & Cooper (1992: 956) initially thought that this specimen belonged to the genus Stilpon Loew because of its dorsoapical arista­like style, parallel­sided (but broad) frons, relatively large male terminalia, and small body size. These features also occur in certain species of Chersodromia , and subsequent trimming of the piece of amber has now allowed a clearer view of the diagnostic features that characterize this genus, particularly those of the face and the gena. Apparent absence of ommatrichia on the eyes may be an artifact of fossil preservation in amber. However, despite the uncertainty with this diagnostic feature of the Drapetini , fusion of the hypandrium and left epandrial lamella also clearly indicates placement of this species within a large clade of the tribe comprised of all drapetine genera except Megagrapha Melander and Austrodromia Collin ( Cumming & Cooper 1992; Cumming, unpubl. data).

ETYMOLOGY. The specific epithet refers to the Dominican origin of the amber harbouring this species.