| 1 | Ratio of radial-medial cross-vein dividing discal-medial cell is 1:1 | 2 |
| – | 1:2 to 1:3 | 3 |
| 2 | Surstylus without large medial protrusions; with small dentate terminus | Perochaeta orientalis Duda, 1926 |
| – | Sternite brush embedded in membrane | 4 |
| 3 | Sternite brush as a free sclerotized lobe | 5 |
| – | Sternite brush with few bristles (ca. 5 short and 5 long bristles); surstylus with large, squat triangular protrusion on inward median | Perochaeta hennigi Ozerov, 1992 |
| 4 | Surstylus without any large medial protrusions | 6 |
| – | Surstylus with large medial protrusions | 7 |
| 5 | Sternite brush with few bristles (ca. 5 short bristles and 5 long bristles); surstylus without large median protrusions | Perochaeta dikowi Ang et al., 2008 |
| – | Medial protrusion emerges dorsally on surstylus; posterior margin of 4th sternite V-shaped with many bristles | Perochaeta cuirassa Ang, 2010 |
| 6 | Medial protrusion emerges ventrally on surstylus; posterior margin of 4th sternite as two distinct lobes with many bristles | Perochaeta lobo Ang, 2010 |