Key to species of the sericata -group

1. At least surface of metaterga leathery, dull.................................................................................................................. 2.

- Dorsal surface shining ................................................................................................................................................ 4.

2. Only caudal parts of paraterga contrastingly light (Figs 14 A–G, J–L). Paraterga less strongly developed, narrower, with only a small incision at best in front 1/3 extent (Figs 14 A, C, E, J & L). No tergal setae borne on evident knobs/ tubercles ....................................................................................................................................................... O. sericata

- Entire paraterga contrastingly light, much broader, largely with an evident, dentiform incision in front 1/3 extent (Figs 1 B, D & K, 7B & D). At least some tergal setae borne on evident knobs/tubercles .......................................... 3.

3. Surface of metaterga rough, microgranulate and rugulose (Figs 1 B–H, K–M). Metatergal setigerous tubercles higher, present also on collum. Paratergal incisions especially prominent (Figs 1 B–E, K & L). ....... O. enghoffi sp. n.

- Surface of metaterga nearly smooth, microgranulate (Figs 7 B–H). Metatergal setigerous tubercles evidently smaller, absent from collum. Paratergal incisions evident, but not so prominent (Figs 7 B & D) .................... O. alutaria sp. n.

4. Adults> 30 mm long and> 4 mm wide. Collum broadly rounded laterally (Figs 12 B & C). Paraterga set high, at least some upturned above dorsum. Sternal cones between male coxae 4 isolated (Figs 12 I & J). ............................... ..................................................................................................................................................... O. parasericata sp. n.

- Adults <30 mm long and <4 mm wide. Collum narrowly rounded to angulate laterally (Figs 5 B &C, 9B & C). Paraterga set high, but remaining below dorsum even in male. Sternal cones between male coxae 4 fused basally into a single lamina (Figs 5 I & J, 9I & J)............................................................................................................................ 5.

5. Bases of paraterga more broadly light (Figs 5 A–H). Legs shorter, about 1.2 (male) or 1.0 times (female) as long as midbody height. Tip of solenophore like an elongate and undulate lobe (Figs 3 C & D, 6) ................... O. subsericata

- Bases of paraterga more narrowly light (Figs 9 A–H). Legs longer, about 1.5 (male) or 1.2–1.3 times (female) as long as midbody height. Tip of solenophore tridentate (Figs 10, 11 A & B). .............................................. O. asticta sp. n.