Key of the species of the genus Hylebainosoma

Only known characteristics concerning the morphology of female vulvae are added.

1 Ocelli missing, body white, without pigmentation............................................................ 2

- With ocelli.......................................................................................... 3

2 Adults with 28 body segments, gonopods with less pronounced posterior branches, inner basal parts of gonopods with structural field covered by small protuberances; coxal processes on 9th legs straight, elongated with slim projection on the apex oriented anteriorly............................................................................ H. cavernicola

- Adults with 30 body segments, gonopods completely with smooth surface structure and two elongated sword-like well separated posterior branches; 9th legs with coxal processes short and broad resembling elk horns armed with denticles on anterior edges; (female vulvae with medial and two elongated lateral postvulval processes)......................... H. gulickai

3 Adults with 28 body segments, body white, pale or without pigmentation, adults with 9 ocelli at most................... 4

- Adults with 30 body segments, yellowish to orange-brown body, adults with 12–14 ocelli............................ 5

4 Anterior branch of gonopods with large lateral lobe on the apex; 9th legs with coxal processes straight, elongated, in the apical part armed by two sharp teeth oriented forward and laterally............................................. H. odici

- Anterior branch of gonopods without lateral lobe on the apex; coxal processes on posterior gonopods straight with anteriorly oriented projection, coxal processes in the second half elongated by narrower arm exceeding the whole 9th legs... H. oltenica

5 Between anterior and posterior branches (cheirites) of gonopod massive medial process with brushy-filled and toothed hook on inner distal side of anterior branch; unpaired medial plate longer than half of the gopopod height with expanded apex; posterior gonopods (9th legs) with slender medially curved arms of coxal processes; (female vulvae with flattened unpaired apically divided postvulval plate)...................................................................... H. tatranum

- Between anterior and posterior branches (cheirites) of gonopod medial discrete process armed by fine denticless; unpaired medial plate reaches less than half the gonopod height without any structure on apex; 9th legs with robust coxal processes (female vulvae without postvulval structures)................................................... H. nontronensis