Seri Kessel & Kessel

Cumming, Jeffrey M. & Cumming, Heather J., 2011, The flat-footed fly genus Seri Kessel & Kessel (Diptera: Platypezidae), Zootaxa 3136, pp. 61-68 : 62

Genus Seri Kessel & Kessel

Seri Kessel & Kessel, 1966: 98 . Type species: Clythia dymka Kessel 1961 [Nearctic], by original designation.

Included species. Seri currently includes S. dymka (Kessel) and S. obscuripennis (Oldenberg) .

Diagnosis. Seri is distinguished from other platypezid genera by the following combination of characters: relatively small flies 3–4 mm in length with body (Figs. 1, 2) uniformly colored grey to black (male darker than female), without abdominal markings in female; head with parafacial bare, frons bearing long frontal setae in male (short setae in female); antenna with scape bare, pedicel with circle of preapical setae extended less than half length of postpedicel, postpedicel small and ovate, arista apical; thorax lacking acrostichal setae, with 3 notopleural setae; wing (Fig. 3) tinted brown in male and lighter greyish brown in female, covered with conspicuous microtrichia, crossvein dm-m less than or subequal to its own length from wing margin, vein M1+2 branched with furcation nearer to crossvein dm-m than to wing margin, cell cua about equal in length to apical section of anal vein (CuA+CuP); legs with mid tibia bearing one apical spur (lacking anteroventral spur); female hind tarsus with soles on anteroventral surface of tarsomeres 3 and 4, tarsomeres 1–3 broad, tarsomere 2 distinctly narrowed ventrally, tarsomere 3 longest; female abdomen with terminalia short, mostly retracted into segment 7, sternite 7 with one or two pairs of strong erect setae; hypopygium of male ( Fig. 4 ) with epandrium terminating in short blunt surstylus, hypandrium with paired elongate ventrally curved apical processes, phallapodeme keel-like, postgonite absent, phallus slender and elongate, sperm pump large and sclerotized with small ejaculatory apodeme.

Distribution. The genus is known from the Palaearctic ( S. obscuripennis ) and Nearctic ( S. dymka ) Regions.

Remarks. Adult specimens of Seri are most easily recognized by their tinted wings, which are conspicuously covered with microtrichia unlike many other platypezids that have clear glassier wings. The venation is also distinctive in that the furcation of M1+2 is nearer to crossvein dm-m than to the wing margin, rather than the more common condition of having the furcation nearer to the wing margin.

According to Chandler (2001) Seri is most similar to the monotypic Palaearctic genus Bolopus Enderlein and is also similar to the small Holarctic/Oriental genus Polyporivora Kessel & Maggioncalda. Unlike most other genera in the Platypezinae the mid tibia of these three genera ends in a single posteroventral spur, with the anteroventral spur being extremely reduced or absent. The antennal scape and parafacial are also bare in these three genera, and the male genitalia includes a large sclerotized sperm pump. Unlike Polyporivora however, Bolopus and Seri both have the wing covered with conspicuous microtrichia, the furcation of M1+2 nearer to crossvein dm-m than to the wing margin, and females that lack a pattern of abdominal markings. Bolopus differs from Seri in that crossvein dm-m is more than 1.5X its length from the wing margin and the antenna has a circle of much longer preapical setae on the pedicel and a subdorsal rather than apical arista. In addition, the male genitalia of Bolopus have a larger pointed surstylus, a shorter hypandrial process and a short straighter phallus.

Kessel and Kessel (1966) and Chandler (1974) both commented, respectively, on how rarely S. dymka and S. obscuripennis appear to be collected, suggesting that each species may be overlooked by specialists because when resting they tend to resemble small muscid flies. However, with increased use of passive trapping techniques such as Malaise traps and pan traps during the last 40 years, many more specimens of Seri would be expected in collections if these flies were more common.

Figures

FIGURE 4. Male genitalia of Seri dymka (Kessel), left lateral view. Abbreviations: cerc—cercus, epand—epandrium, ej apod—ejaculatory apodeme, hypd—hypandrium, hypd lb—hypandrial lobe, hyprct—hypoproct, phapod—phallapodeme, ph—phallus, spm sac—sperm sac, sur—surstylus. Scale in mm.