Rhagio Fabricius, 1775

Kerr, Peter H., 2010, 2592, Zootaxa 2592, pp. 1-133 : 85-88

Genus Rhagio Fabricius

Figs. 17, 29, 35, 37, 39, 56–57, 79, 101–102, 122, 130, 141, 170, 176, 184–185, 190.

Rhagio Fabricius 1775: 761 . Type species Musca scolopacea Linnaeus 1758 , by subsequent designation of Latreille 1810: 443.

Leptis Fabricius 1805: 69 (unjustified emendation for Rhagio Fabricius 1775 ). Type-species Musca scolopacea Linnaeus 1758 , automatic.

† Palaeohilarimorpha Meunier 1902: 400 . Type species Palaeohilarimorpha bifurcata Meunier 1902 , by monotypy.

Rhagina Malloch 1932a: 117 . Type species Leptis incurvata Meijere 1911 . New synonymy. See notes below.

Rhagionella Szilády 1934a: 239 (as subgenus). Type species Nemotelus maculatus De Geer 1776 , by original designation.

Rhagiella Szilády 1934a: 240 (as subgenus). Type species Rhagio lineola Fabricius 1794 , by original designation.

Diagnosis. The monophyly of the species of Rhagio is supported by a unique feature found in the larva. All Rhagio larvae have a saw sclerite attached ventrally to the basal mandibular sclerite. The autapomorphic nature of this character state is evident among tabanomorph larvae. However, the larva of many Rhagio species remain undescribed and the larva of putatively closely related genera such as Desmomyia and Atherimorpha , among many other rhagionid taxa, are also not known.

Rhagio species are delicate to fairly robust flies, variably sized (4.2 to 18 mm); black, gray, brown, orange-brown, yellow or yellow and black. Wings are hyaline or infuscate, with or without markings; male holoptic or dichoptic, eyes separated in female; first flagellomere subcircular, laterally compressed, with terminal arista arising ventrally or from central position; mandibles absent; laterotergite setose; M 3 present; tibial spur formula 0:2:2; hind tibia with short macrochaetae when present; tergite 9 without ventrolateral arms; female spermathecal ducts without accessory glands. Rhagio is distributed throughout the Holarctic Region. Rhagio species are most commonly confused with species of Chrysopilus , but may be distinguished by having two hind tibial spurs; an arista that is nearly bare; and a prominently setose proepimeron. In India, and perhaps in surrounding areas, Rhagio may be distinguished from local Desmomyia by having the scape approximately the same size as pedicel and in the male, first tarsomere not enlarged. Rhagio is very similar in form to Atherimorpha , although their distributions are not sympatric. Rhagio may be distinguished immediately from Atherimorpha by having an aristate antenna.

Description. Head. Clypeus bulbous. Scape approximately same size as pedicel. First flagellomere. First flagellomere of antenna enlarged; basally rounded in cross section or laterally compressed, bearing fused or arista-like extension. Eyes inconspicuously setulose; in male, holoptic or dichoptic (dichoptic in female), not flattened dorsally; ommatidia evenly distributed of equal size or ommatidia larger dorsally with smooth transition to slightly smaller ommatidia ventrally. Labella with pseudotracheae, length variable. Theca short and stout, lateral thecal sclerites separated. Palpus one-segmented, often with constriction, making it appear that there are two palpomeres. Stipes convergent toward one another medially or surrounded by membrane above theca, directed posteriorly. Cardo not swollen. Lacinia shorter than palpus; tip not serrated. Mandibles absent. Cibarial pump long, clearly not as wide as long. Cornu nearly as long as or longer than cibarial pump. Pharyngeal pump narrow along most of length, mostly flat along its length, approximately same length as cibarial pump.

Thorax. Mesonotum with or without vittae. Dorsocentral bristles absent, all dorsal setae of equal length. Anepisternum bare ( R. maculatus De Geer , R. dichomaticus Chillcott ), setulose on dorsal margin only, or throughout posterior half of sclerite. Laterotergite setose, on ventral half (katatergite) only. Postspiracular scale absent. Proscutellum present or absent. Subscutellum not enlarged nor lengthened; inconspicuous. Wing hyaline or lightly infuscate; with or without markings. Wing with or without pterostigma. Lower calypter reduced. Upper calypter well developed, with broad curvature, lobe-like, width twice length or less. Costa ends before or approximately at wing tip Humeral crossvein well developed. Sc-r crossvein present, well developed, positioned distal to h by more than length of h. Dorsal side of R 1 setulose, ventral side bare. All other wing cells and veins bare. R 2+3 nearly straight or sinuous; longer than but less than twice as long as R 5; apical third ultimately bends either slightly anteriorly or back toward wing tip. Base of R 4 –R 5 fork proximal of, directly above, or distal of distal end of cell dm. R 4 at base strongly curved or angled; leads directly to wing margin or with short proximal offshoot at point of curvature near base; nearly straight or sinuous apically (as in R. tuberculatus ( Yang et al. 1997: 245)) ; anterior to, ending at, or posterior to wing tip. R 5 clearly longer than R 4+5 or about as long as R 4+5 (r-m to R 4 origin). M 3 present. Cell m 3 parallel-sided at margin. Origin of CuA 1 at cell bm. CuA 2 greater than 1/2 length of posterior vein of cell bm and greater or less than 2/3 length of posterior vein of cell bm. Alula with narrow or broad curvature, rounded evenly. Anal lobe well developed. Cell cu p open or closed. Halter knob approximately 1/2 length of stem. Tibial spur formula 0:2:2. Hind coxal tubercle absent or present. Hind femora with or without ventro-apical swelling. Hind tibial macrochaetae absent or present; when present, short. First hind metatarsus of male not swollen. Postmetacoxal bridge reaches internal base of metasternal furcum as incomplete, thin extension.

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 length variable, wider than long to much longer than wide. Male terminalia with epandrium simple, not containing hypandrium ventrally. Epandrium wider than long, strongly notched anteriorly. Tergite 10 absent. Hypoproct with or without setae. Cercus attached to hypoproct, displaced away from epandrium; partially displaced from one another, separation distance approximately half width of single cercus. Cerci, in posterior view flat. Hypandrium separated from gonocoxites by complete or 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 long, reaching beyond anterior margin of hypandrium; laterally compressed. Aedeagal tines absent. Endoaedeagal process present, very reduced (as in R. plumbeus ), or apparently absent (as in R. punctipennis ). Female terminalia with three spermathecae, spherical or elliptical, lightly sclerotized or without sclerotization. Spermathecal ducts longer than five times length of sternite 9, but not so long as to be difficult to measure. Spermathecal duct accessory glands absent. Ejection apparatus of spermathecal ducts thickened, lightly sclerotized, surface furrows that run at an angle. 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, free, held in horizontal plane. Tergite 10 length aproximately equal to half measured width, or longer. Sternite 10 entire, roughly pentagonal, pointed posteriorly; posterior half below first cercal segment. Cercus two-segmented. First segment of cercus not elongate, with or without ventral process. Ventral lobes of first segment of cercus curve ventrally towards one another to form ring, visible in posterior perspective. Basal cercal segment adjacent dorsally. Second cercal segment not elongated, with or without apical sensory pits.

Larva. Body with 11 segments, amphipneustic. Thoracic segments with creeping welts ventrally. Head capsule not folded within second segment, composed of a single, undivided plate (dorsal plate); less than 4.5 times longer than greatest width (2 width: 5.5 length); not cone-shaped. Mandibular brush present, associated with simple fold of cuticle. Mandibular hook canal with apical opening. Hook serrate, transversely smooth. Stiff microsetae pointing anteriorly on dorsal ridge of mandibular hook absent. Labral teeth developed, sclerotized; in single row. Maxilla sclerotized (and thrice toothed, as in Ptiolina ). Saw sclerite of mandibular base present. Maxillary palpus soft, segments poorly differentiated; three maxillary palpomeres. Antenna last segment entire (nub). Antenna three-segmented. Unpaired salivary pump absent. Posterior tentorial expansion free, with thin extension produced dorsally.

Biology. Adult Rhagio have been reported as predaceous on other insects ( Kellogg 1908; Leonard 1930; Narchuk 1969, 1988; Paramonov 1962) but this has never been confirmed and is unlikely given their gawky movements and the generalized morphology of their mouthparts. Rhagio scolopacea has even been reported as a bloodfeeder ( Ferguson 1915; Heim & Leprevost 1892; Lindner 1925) but these accounts are certainly false. It is remarkable, actually, how little is known regarding the adult stage of these common, widespread flies. Rhagio adults are generally active between April and September.

Rhagio Fabricius is distributed throughout the Holarctic reaching its southernmost extension in the Oriental Region where it is found in Java and Sumatra. Species formerly placed in Rhagina are restricted to China and Java.

Literature. Leonard (1930) gives a key to the species of North America. James (1964, 1965b) revised the species of western North America and Chillcott (1965) revised the species of eastern North America. Narchuk (1969) provides a key to the species of Russia. Yang et al. (1997) give a key to species of China.

Notes. The Catalogue of Palaearctic Diptera (Majer 1982) errs in listing Leptis tristis Schummel 1837:109 twice; as a junior synonym of Ptiolina obscura and as a valid species within the genus Rhagio . The species is recognized here as Rhagio tristis (Schummel) .

The phylogenetic analysis of morphological characters ( Fig. 192) does not clarify the position of Rhagina with respect to the Rhagio lineage. However, I maintain that until a more targeted taxon sampling of this area is used to test and confirm the monophyly of Rhagio sensu stricto, the concept of Rhagina remains uncertain and should be treated as a junior synonym of Rhagio based on the observations noted below.

Yang et al. (1997: 187) state that Rhagina males lack tergite 10, whereas in Rhagio , it is present. However I find the male genitalia of these taxa indistinguishable; both lack T10. Although the wing in Rhagio incurvatus (Meijere) is distinctive, there is an apparent grade of states for this character within the group, especially as one examines the wing of Rhagio sinensis Yang & Nagatomi which has a sinuous R 2+3 vein, but not distinctively so, and not far removed from venation found in some R. hirtus (Say) and R. dichomaticus Chillcott specimens. Another distinctive feature of Rhagina emphasized by Nagatomi (1982a) and Yang et al. (1997) is a prominent ventro-apical ‘hump’ on the hind femur. Despite this, Yang et al. (1997: 115) indicate that the presence or absence of such a hump does not necessarily determine the genus Rhagina . I have also noticed that this may be a variable character in both Rhagio and Rhagina . Although most commonly absent in Rhagio , I have observed the hind femoral process in an undescribed Rhagio species from Laos.