246 PROCEEDINGS OF THE NATIONAL MUSEUM tol. lu 



Rec. Queen Victoria Mus., vol. 2, p. 17, 19-i7a; Rec. Queen Victoria Mus., 

 vol. 2, p. 23, 1947b.— Hennig, Die Larvenformen Dipt., vol. 3, p. 91, 1952.— 

 Paramonov, Pac. Sci., vol. 9, p. 23, 1955. — Trojan, Ann. Zool., vol. 16, 

 p. 75, 1956. 



Ogeodes, Gimmerthal, Bull. Soc. Imp. Nat. Mos., p. 167, 1847. — Schlinger, Wasm 

 Journ. Biol., vol. 11, p. 320, 1953 (lapsus). 



Ogkodes, Schiner, Vorh. Zool.-Bot. Ges. Wein., vol. 15, p. 89, 1865.— Hennig, Di.- 

 Larvenformen Dipt., vol. 3, p. 624, 1952 (lapsus). 



Arcrodes, Froggatt, Australian Ins., p. 298, 1907 (lapsus). 



Type of genus: Musca gibbosa Linnaeus as Syrphus gibbosus 

 Fabricius (by subsequent designation of Latreille, 1802, p. 432, one 

 species). 



Generic diagnosis:^ Small to medium-sized (2.5-10 mm.), gib- 

 bose, typically black or brown with yellow or white posterior fasciae 

 on tergites (pi. 5, fig. 29), somewhat more irregular on sternites, or 

 varicolored brown or black with white, yellow, or orange markings 

 (pi. 5, fig. 30); pile present over most of specimen, long or short. 



Head with bare holoptic eyes in both sexes (pi. 5, fig. 28); antenna 

 3-segmented, inserted just above mouth, segment i round and short, 

 segment ii of equal or slightly larger size, with or without short 

 bristle, segment in stjdiform with single lateral sensory pit, with 

 one to three short apical setae and with basal bristle, or short and 

 blunt with five to six longer apical setae (pi. 5, figs. 23, 25, 27); 

 proboscis present in living or dead specimens or absent in dead ones 

 (pi. 1, fig. 3), if absent, the mouth area is covered by thin membrane; 

 lateral ocellus present on small or rarely large vertex (pi. 5, fig. 28). 



Thorax arched in front, scutellum large, well-raised (pi. 5, figs. 22, 

 24, 26), wing venation imperfect to extremely weak, costal vein 

 reaching wing tip, m-cu and r-m crossveins present or absent, but 

 usually veins present include at least Sc, Ri, R4+5, M4, and A; costal 

 and subcostal cells present, usually with first, sometimes with second, 

 basal cell present (pi. 3, figs. 6-13; pi. 4, figs, 14-21); legs usually 

 slender, hind femur often swollen, tarsus with paired simple claws 

 and three pul villi. 



Abdomen arched dorsall}^, flattened ventrally, tapering (male) or 

 blunt (female) at apex, usually as high as wide, with sLx visible seg- 

 ments (pi. 5, figs. 22, 24, 26); male genitalia partl}^ concealed under 

 tergite vi, consisting of bowl-shaped 9th tergite, claspers, aedeagus, 

 and ejaculatory apodeme, all more or less held in place by tergite ix 

 (pi. 6, fig. 31); female genitalia simple, with obvious cerci and often 

 with row of minute or larger setae along posterior margin of sternite ix. 



'For adult. Descriptions of immature stages will be found in the biology section. 



