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