1	Abdominal tergites I–VII with median tubercles (Fig. 7B)	O. jessicae
–	Abdominal tergites without median tubercles	2
2	Outer margin of hind tibiae without a row of long and thin setae (Fig. 12B)	O. orontensis
–	Outer margin of hind tibiae with a row of long and thin setae (e.g., Fig. 12A)	3
3	Caudal filament much shorter than cerci (Fig. 8A); frons slightly carinate (Fig. 8B)	O. elisabethae
–	Caudal filament subequal in length to cerci (e.g., Fig. 10A); frons may or may not be slightly carinate	4
4	Frons slightly carinate (Fig. 4B); lamella of gill I minute, abdominal marking as in Fig. 4A, although this can be less distinct	O. lawrencei
–	Head without carina, lamella of gill I small but well visible; abdomen without contrasted markings (e.g., Fig. 10A)	5
5	Posterolateral projections of the abdomen clearly divergent from body axis (Sroka et al. 2019, fig. 7A–B)	O. villosus
–	Posterolateral projections of the abdomen parallel to body axis (e.g., Fig. 5B)	6
6	Fibrillae of gill I as long as lamella; outer margin of hind tibiae with a row of rather short setae (Fig. 5A); body coloration dark brown (Fig. 6A)	O. dobbsi
–	Fibrillae of gill I much longer than lamella; outer margin of hind tibiae with a row of long setae (Fig. 12A); body coloration light brown (Fig. 10A)	O. skhounate