Desmomyia Brunetti, 1912

Kerr, Peter H., 2010, 2592, Zootaxa 2592, pp. 1-133 : 84-85

Genus Desmomyia Brunetti

Figs. 73, 95, 140, 169.

Desmomyia Brunetti 1912: 462 . Type species Desmomyia thereviformis Brunetti 1912 , by original designation.

Diagnosis. Desmomyia is characterized by having the antennal scape elongated, clearly longer than the pedicel; and the male hind first tarsomere enlarged. Both of these character states are autapomorphies for the genus.

Species of Desmomyia are mid-sized flies (5.0–6.7 mm) of gray, black, or brownish coloration; legs with some yellow or concolorous dark brown to black; wings lightly infuscate, with light markings; male holoptic (eyes widely separated in female); laterotergite setose, M 3 present, tibial spur formula 0:2:2, and hind tibia with or without short macrochaetae. Desmomyia is restricted to India and China. It is most likely to be confused with Rhagio , which is very similar in general appearance, and overlaps Desmomyia in its geographic distribution. The males of Desmomyia are distinguished by the autapomorphic characters of the antenna and hindleg mentioned above and may also be separated from nearly all Rhagio males by having pronounced, swollen parafacials. Females may be separated reliably from Rhagio by having the scape longer than pedicel. Desmomyia is distinguished from Chrysopilus by having two hind tibial spurs and by the absence of scale-like thoracic setae, in addition to the autapomorphic character states mentioned above.

Description. Head. Clypeus bulbous. Scape clearly larger than pedicel. First flagellomere laterally compressed, enlarged basally, bearing fused or distinct arista-like extension. Eyes inconspicuously setulose; in male, ommatidia evenly distributed, of equal size, or ommatidia split into dorsal and ventral areas and smaller ventrally, holoptic, not flattened dorsally. Parafacials in male swollen. Labella with pseudotracheae, as long as palpus or longer. Theca short and stout. Palpus one-segmented.

Thorax. Mesonotum with or without vittae. Dorsocentral bristles absent, all dorsal setae of equal length. Anepisternum setulose on dorsal and posterior margins. Laterotergite with katatergite swollen, differentiated from anatergite. Laterotergite setose, on ventral half (katatergite) only. Postspiracular scale absent. Proscutellum absent. Subscutellum not enlarged nor lengthened; inconspicuous. Wing hyaline, without markings. Pterostigma present. Lower calypter reduced. Upper calypter well developed, with broad curvature, lobe-like, width twice length or less. Costa extends to wing tip. Humeral crossvein well developed. Sc-r crossvein weakly developed, positioned distal to h by approximate length of h. Dorsal side of R 1 setulose, ventral side of R 1 bare. All other wing veins without setulae. Apical third of R 2+3 ultimately bends anteriorly slightly, toward leading edge of wing margin. Length of R 2+3 about as long as R 5. Base of R 4 –R 5 fork proximal to or directly above distal end of cell dm. R 4 at base relaxed, not strongly curved; nearly straight apically. R 4 and R 5 contain wing tip. R 5 clearly longer than R 4+5 (r-m to R 4 origin). R-m crossvein proximal to one-third of discal cell. Origin of CuA 1 at cell bm. M 3 present. Cell m 3 convergent at margin. Length of CuA 2 v. posterior vein of cell bm less than 1/2 length of posterior vein of cell bm. Alula narrow curvature, rounded evenly. Anal lobe well developed. Cell cu p closed. Halter knob approximately 1/2 length of stem. Tibial spur formula 0:2:1. Hind coxal tubercle absent. Hind tibial macrochaetae present, short. First hind metatarsus of male swollen.

Abdomen. Abdominal segments 5–10 evenly tapered from segments 1–4. In female, tergite 7 much longer than wide; intersegmental membrane between segments 7 and 8 especially long. Sternite 8 sclerite entire, not divided into two segments, length wider than long or as wide as long. Male terminalia with epandrium simple, not containing hypandrium ventrally. Epandrium wider than long, modestly curved anteriorly. Tergite 10 absent. Hypoproct tomentose, setae absent. Cercus base held underneath epandrium. Cerci partially displaced from one another, separation distance approximately half width of single cercus. Cerci, in posterior view flat, held in horizontal orientation. Hypandrium separated partially from gonocoxites by incomplete suture. Gonocoxite with sinuous dorsal ridge, leading to gonocoxal apodeme. Gonocoxal apodemes short or long enough to reach anterior margin of hypandrium. Sperm sac bulbous, without paired swellings ventrally. Lateral ejaculatory processes present, integrated into sperm sac membrane. Ejaculatory apodeme moderately long, reaching anterior margin of hypandrium or long, reaching beyond anterior margin of hypandrium; laterally compressed. Aedeagal tines absent. Endoaedeagal process present. Female terminalia with three spermathecae, elliptical, lightly sclerotized. Spermathecal ducts longer than five times length of sternite 9, but not so long as to be difficult to measure; not inflated at base of spermathecae. Spermathecal duct accessory glands absent. Ejection apparatus of spermathecal ducts not sclerotized, without surface furrows. Spermathecal duct junction thickened. Common spermathecal duct thickened; short, shorter than longest diameter of genital chamber. Genital chamber oval, moderately sized. Accessory gland posterior to genital chamber inconspicuous, easily overlooked even after staining. Sternite 9 anterior end pointed; posterior end with broad lateral extensions which are joined medially with seam, in the vertical plane. Tergite 10 not greatly reduced. Sternite 10 entire, roughly pentagonal, pointed posteriorly; posterior half below first cercal segment. Cercus two-segmented. First segment of cercus not elongate, without ventral process. Ventral portions of first segment of cercus do not curve ventrally, towards one another, to form ring. Basal cercal segment adjacent dorsally. Second cercal segment not elongated, without apical sensory pits.

Larva. Unknown.

Biology. Desmomyia is known only from India ( Brunetti 1912; Yang et al. 1997).

Literature. Yang et al. (1997) illustrate the species from China.