Medeventor Wheeler

Wheeler, Terry A., 2007, Two new genera of oscinelline Chloropidae (Diptera) from Costa Rica, Zootaxa 1413, pp. 47-53 : 48

Medeventor Wheeler , gen. n.

Type species: Medeventor nubosus sp. n. (by present designation)

Diagnosis: Very large (4–5 mm) Oscinellinae with extensively setulose body and reduced setae, especially on the head; weak, broad facial carina; broad, rugose gena.

Description: Chloropidae , Oscinellinae . Head about as high as deep in lateral view; frontal triangle distinct, bare except for row of setulae along margin; frons densely setulose, most cephalic setae short and weak, fronto-orbital, vertical, ocellar and postocellar setae barely differentiated from surrounding setulae, ocellar and postocellar setae convergent; eye bare, rounded; gena broad, swollen, divided into densely pruinose dorsal region and broader, shining, rugose ventral region, postgena swollen, setulose ( Fig. 1 ); vibrissal angle not projecting, vibrissa short; face with broad but weak carina between antennal bases, less pronounced ventrally ( Fig. 2 ); antenna with scape and pedicel short, first flagellomere rounded, arista pubescent; proboscis short; palpus elongate, swollen ( Fig. 1 ).

Scutum convex, densely setulose, thoracic setae weak, 1 postpronotal, 1 anterior and 1–2 posterior notopleural, 1 postsutural supra-alar, 1 postsutural intra-alar, 1 dorsocentral seta; scutellum short, strongly convex, with long, dense lateral and dorsal setae, apical and subapical scutellar setae longer and stronger than surrounding setae; thoracic pleurites bare except for dorsal patch of setulae on katepisternum. Wing hyaline but heavily microtrichose, alula and anal angle well-developed, cell c long and broad, especially in male, second costal sector longer than third; crossvein r-m beyond midpoint of cell dm; crossvein dm-cu perpendicular or slightly oblique; pronounced ventral bulge at wing base ( Fig. 3 ). Legs without outstanding setae or spurs; femoral organ not differentiated from surrounding setulae; tibial organ elongate oval, dark, velvety.

Abdominal tergites with long, dense setae; sternites narrow but distinct, with long setae; male spiracles 3– 5 in membrane near lateral margin of tergite.

Male postabdomen: remnant of sternite 6 median, symmetrical, represented by a pair of sensory setulae and a patch of microtrichia distinct from surrounding membrane; sensory setulae of sternite 7 present posterior to this ( Fig. 4 ); dorsal pregenital sclerite large, symmetrical, divided by a transverse suture into narrow anterior and broad posterior portions, posterior portion densely setose; spiracles 6 and 7 in membrane ventral to lateral margin of dorsal sclerite; epandrium simple, convex, with short setae; surstylus simple, elongate, freely articulated with epandrium; hypandrium open posteriorly; pregonite fused with postgonite, sclerotized; postgonite with ventral setulae and campaniform sensillae; basiphallus elongate, sclerotized, distiphallus short, membranous; phallapodeme simple, phallic guide well sclerotized, fused anteriorly with hypandrium ( Fig. 7 ); cerci broad, flat, setulose; subepandrial sclerite well-developed, with setulose lobe dorsomedial to surstyli ( Fig. 7 ).

Female terminalia not modified, cerci separate, dorsoventrally flattened, broad, setulose.

Etymology: The generic name is an anagram of Monteverde, the type locality of the type species. It is treated as masculine.

Remarks: Medeventor appears to be most closely related to the Old World genera Lipara Meigen and Pseudeurina de Meijere ( Andersson 1977, Kanmiya 1983). These three genera share an extensively setulose body, large size, a broad rugose gena and a broad facial carina (less developed in Medeventor ). However, Medeventor cannot be accommodated in either of those genera without significantly modifying their current limits, and the autapomorphic characters of the type species justify erection of a new genus.

The male postabdomen of Medeventor is atypical in that ventral, symmetrical remnants of sternites 6 and 7 are present. In the subfamily Siphonellopsinae , sternites 6 and 7 are often retained, but are usually asymmetrical, as is the case with many other families of acalyptrate Diptera ( Andersson 1977) . The reduction and loss of sternites 6 and 7, and the secondary symmetry of the postabdomen are apparently apomorphic for Oscinellinae plus Chloropinae (e.g., Andersson 1977). Although the postabdomen is symmetrical in Medeventor , the distinct remnant of sternite 6 is unusual among Oscinellinae .

Figures

FIGURES 1 – 7. Medeventor nubosus. 1. head, lateral. 2. head, anterior. 3. wing. 4. male abdomen, posterior portion, ventral. 5. male genitalia, lateral. 6. male genitalia, posterior. 7. male genitalia, ventral. Abbreviations: st — sternite; ses — subepandrial sclerite. Scale bars = 1.0 mm (Fig. 3), 0.2 mm (Figs. 6 – 8).