1	Calypter hairs and often calypter margin white	2
–	Calypter hairs light to dark brown; margin usually also dark	4
2	Postpronotum, notopleuron and lunule light yellow. First flagellomere with anterodorsal margin angled. Eye 4.3–5.0 × higher than gena at highest point. Epandrium with large transverse carina (Figs 559, 560)	C.superciliosa (Zetterstedt)
–	Postpronotum, notopleuron and lunule brown. First flagellomere rounded. Eye 6.8–10.7 × higher than gena at highest point. Epandrium without carina	3
3	Wing length 2.3–3.4 mm. Anterior section of fronto-orbital plate up to 1/3 width of frons. Only apex of fore femur light yellow for length equal to width of femur apex; mid and hind femora with extreme apex fading to brownish or yellowish. Ocellar spot dark, well-defined. Bulb of mesophallus bulging ventrally over stem. Distiphallus slender, hooked with slender bell-shaped apex (Figs 543, 544)	C.incisa (Meigen)
–	Wing length 1.8–2.2 mm. Anterior section of fronto-orbital plate not exceeding ¼ width of frons. Apices of all femora light yellow for length equal to width of femur apex. Ocellar spot ill-defined, sometimes faded. Bulb of mesophallus not strongly overlapping stem. Distiphallus stouter, straighter (Figs 557, 558)	C.pygminoides Spencer
4	At least distal 1/3 of femora yellow. Fronto-orbital plate and ocellar triangle yellow in part	5
–	Only apex of fore femur yellow, sometimes with mid and hid femora also somewhat yellowish apically. Head entirely brown to dark brown (rarely with yellowish border around ocellar tubercle)	6
5	At least distal ¾ of femora yellow, sometimes only with narrow brown region at base. Fourth dorsocentral almost as small as surrounding setulae. Distiphallus straight	C.kennethi Zlobin
–	Distal 1/3–1/2 of femora yellow. Fourth dorsocentral at least 1/3 length of first dorsocentral. Distiphallus strongly twisted to right (Figs 548, 549)	C.muscina (Meigen)
6	Ring around eye shallow, not projecting anteriorly. First flagellomere rounded. Eye 6.0–8.3 × higher than gena at highest point. Six rows of acrostichal setulae. Hairs on calypter dark brown. Only left paraphallus distinct, directed laterally. Mesophallus stem bulging basally; apical bulb overlapping mesophallus. Distiphallus tubules mostly clear with lateral sclerotised band, ?-shaped with small apical cup (Figs 553, 554)	C.pygmaea (Meigen)
–	Ring around eye very pronounced, projecting anteriorly. First flagellomere with shallow dorsal angle. Eye 3.0–4.1 × higher than gena at highest point. Four rows of acrostichal setulae. Hairs on calypter light brown. Paraphalli weakly developed, almost indistinct. Mesophallus narrow in lateral view; apical bulb small, globose. Distiphallus tubules dark, slightly curved at base, expanded apically into broad, dark cups (Figs 565, 566)	C.ungula sp. nov.