1	Wings unmarked except for indistinct small spot on dcc and black border on costa	Semachrysa dammermanni (Esben-Petersen, 1929)
–	Wings with numerous brown or black markings	2
2	Forewing with strong dark brown marking at base of outer gradate series	3
–	Forewing without dark markings in this position (sometimes very faint)	4
3	Large dark brown marking present on fourth posterior marginal crossvein of forewing; small marking present on Cu2; male genitalia with arcessus narrow, without ridges; female genitalia with duct of spermatheca twisted, vela very long	Semachrysa contorta Brooks, 1983
–	Small mark present on fourth posterior marginal crossvein of forewing, but with large brown mark on dcc; male genitalia with arcessus broad, ridged; female genitalia with duct of spermatheca and vela short	Semachrysa matsumurae (Okamoto, 1914)
4	Single median marking on vertex either between, or immediately posterior to antennal bases	5
–	Medial marking absent on vertex between or immediately posterior to antennal bases	7
5	Extensive dark markings in basal portion of forewing from R vein to posterior margin of wing; basal four to five crossveins between R and Rs converging posteriorly; three crossveins between Cu1 and Cu2, 1st posterior marginal crossvein forked with posterior arm joining to Cu2 petiolate to margin	Semachrysa jade sp. n.
–	Dark markings in basal portion of forewing restricted to basal cells along posterior margin of forewing; basal four to five crossveins between R and Rs parallel; two crossveins between Cu1 and Cu2, 1st posterior marginal crossvein not forked and separate from Cu2 to wing margin	6
6	Hindwing with distinct brown marking on dcc and faint shading on posterior marginal crossveins	Semachrysa wallacei Brooks, 1983
–	Hindwing with only faint markings on dcc or forked posterior forked marginal crossveins, but marking present on fourth posterior marginal crossvein	Semachrysa picilabris(Kimmins, 1952)
7	Prominent markings at base of inner gradate series of forewing and on fourth posterior marginal crossvein; male abdominal setae dense and fine	Semachrysa papuensis Brooks, 1983
–	Forewing lacking above combination of markings, though pale suffusion may be present	8
8	Two spots on frons below antennae	Semachrysa cruciata (Esben-Petersen, 1928)
–	Three spots on frons below antennae	9
9	Brown band extending from along inner margin of eye from postocular lobe to anterior edge of vertex	Semachrysapolysticta Brooks, 1983
–	Brown band absent; isolated mark on postocular lobe	10
10	Fore and hindwing lightly suffused with brown, particularly along posterior margins, distinct spots absent	Semachrysa minuta Brooks, 1983
–	Fore and hind light brown suffusion admixed with dark markings	11
11	Darkest marking on forewing on dcc	12
–	Darkest marking on forewing on fourth posterior marginal crossvein	13
12	Forewing dcc with large marking, extending from anal veins to second cubital cell (c2); many crossveins with pale brown suffusion including Rs and inner gradate series	Semachrysa sagitta Brooks, 1983
	Forewing dcc with small marking, not extending to anal veins or c2; all crossveins pale	Semachrysa nigribasis (Banks, 1920)
13	Small species, forewing length 7.5 mm; four inner gradate and five outer gradate crossveins	Semachrysa hyndi Brooks, 1983
–	Larger species, forewing length 9.0 mm or greater; at least six inner gradate and outer gradate crossveins	14
14	Forewing length 9.0 mm, faint marking on dcc with extensive brown suffusion; female spermatheca with deep ventral impression	Semachrysa decorata(Esben-Petersen, 1913)
–	Forewing length 13.0 mm, dcc lacking dark markings and brown suffusion posteriorly; female spermatheca with shallow ventral impression	Semachrysa claggi (Banks, 1937)