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Body 9mm.
Probably wrong place to put it, but Key to Australian species of Oides (excluding poorly known bistrivittata, flexuosa and vittata), that I modified from Lea 1925 key. Not all steps are couplets. Use other sources to confirm IDs.

1. Prothorax with dark markings, not entirely pale. = 2.
   *Prothorax entirely pale. = 3.

2. Prothorax with large black blotch, sides pale. Each elytron with a wide black longitudinal vittae well separated at suture. Scutellum black. Legs black but femur base pale. Sterna pale, abdomen black except at sides. Antennae brownish-black, basal joints pale. SthQld, 9.5mm. = dorsosignata.
   *Prothorax black, with pale edges. Each elytron with 2 vittae conjoined posteriorly but not reaching apex. Scutellum pale. Underside brown to pale, legs black but femur base pale. Antennae black-brown, segs 1-3 pale. 10mm. = seminigra.
   *Prothorax with 2 small black spots. Yellow. Black also at base of head, apex of each antennal segment (each is bicolored), and tarsi. Each elytron with 4 dark (or purplish or bronze) vittae with sutural one combined (suture dark, so looks like 7 vittae across whole elytra). The 3 non-sutural vittae all join posteriorly, the outer 4th is shorter than the others. (Compare to tigrina where the suture is pale). NthQld, 7-10mm. = bimaculicollis.

3. Elytra entirely pale. = antennalis or plantarum (Lea could not tell them apart). O. antennalis is described as having tarsi darkened. Antennae nearly long as body, with apex of segs 1-4 dark, upper halves of 5-8 dark, and all of 9-11 dark. Qld, 7.4mm. O. plantarum said to be more narrowly oval than antennalis, with much shorter antennae (slightly longer than half body – a sexual difference?) and sparser punctures. Antennae dark at apex of segments 2-4 and all of 5-11. Tibiae apex, tarsi also dark. NthQld, 8.5mm.
   *Elytra partly dark. = 4.

4. Elytra mostly dark, narrowly pale only at sides and suture. = 5.
   *Each elytron with conspicuous 3-shaped black apical mark. Bright yellow. Black also on head, most of antennae, abdomen, and a 3-shaped mark on elytra (begins narrowly on suture at apical third, dilates at apex, curves around on the side, from about the middle of which it turns inward to end as a rounded knob). Coen, 8mm. = arithmetica.
   *Each elytron rear 2/3 with a wide and long black patch. Antennal segments 1-6 with apices dark, 7-11 black and pubescent. Legs pale, tibial apices and tarsi dark. Underside pale except darker centres of abdominal segments. 9mm. = alitersignata.
   *Each elytron with large elongate bluish spot posteriorly. Black antennae, mandibles, and tibiae (except the base), tarsi, and most of abdomen (abdomen can vary, with dark confined to middle and part of basal 2-3 segs, or segs 1-4 with pale sides and all of seg 5 yellow). NT, 6.8-8.5mm. = tepperi.
   *Elytra with spots. = 6.
   *Elytra vittate (longitudinally striped). = 9.

5. Suture conspicuously pale, form narrow. Elytra (except for the lateral and apical sutural edges) blue-black. Elytral thin pale margin reaches apex. Abdomen pale. Ant seg 3,4 equal, 2 v short. NthWA NT, 8mm. = soror.
   *Suture obscurely or not at all pale, form robust (elytra wider than soror). Elytra blue or olive green with very thin pale margins (not reaching apex). Reddish eyes, pronotum, underside and legs. Abdomen black. Antenna red-brown, segments 1-3 red. NSW PNG, 8.5mm. = laetabilis.
   *Suture not pale. Elytra dark green but closely edged with yellow on sides. Abdominal segments 1-3 brown except sides. Black tibiae and tarsi. Antennae 2/3 length of body, black, segments 1-2 pale. SthQld, 8.5mm. = viridipennis (I’m unsure how/if it differs from laetabilis, or the strength of the characters listed).

6. The elytral spots are 6 in number (2 transversely placed just before middle, 1 larger irregular shape to rear). Some specimens have the marks in the same position but tend to merge (subsp. uniplagiata) or are small (subsp. sexmaculipennis). = biplagiata.
   *The elytral spots are 4 in number. = 7.

7. Head with 2 spots at base. The basal spot on each elytron is transversely rounded and nearer the suture than the side margin. The subapical oval spot is oblique, its front subtruncate, commencing just past middle of the elytron and all but reaching the apex. Antennae slightly longer than half body, segments 2-3 pale, apex of segments 4–6 and all of 7-11 dark. Tibiae apex and tarsi dark. Qld, 10.2mm. = velata.
   *Head pale, lacks dark spots. = 8.

8. Antennae entirely pale, elytral spots black. Each elytron with large black square patch at base not reaching suture or side, plus equally broad semitriangular patch near apex. Scutellum and all underside pale. CapeYk, 10.6mm. = albertisi.
   *Antennae partly black, elytral spots purplish (or greenish or bronzy). First 2 elytral spots are basal and almost circular, the 2 subapical spots are larger and less rounded. The two sets of spots are narrowly separated at suture and sides. The pronot is more uneven than in albertisi and has larger punctures. Antennal segs 2,3 partly dark, and the last 5 or 7 segs are black. = continentalis.

9. One dark vitta on each elytron. = 10.
   *Two dark vittae on each elytron, joined at apex not base. Scutellum yellow. Head pale. SthQld, 8.5-10mm. = fryi.
   *Three dark vittae on each elytron, free at both base and apex. NthQld. = sexlineata.
   *Four dark vittae on each elytron, not reaching apex. Vittae 2,3 join posteriorly and their common stem then joins the other 2 vittae. The external (side) vitta is short, occurring in the rear third of elytra. 8.5mm. = tigrina.

10. Elytra highly polished and not shagreened. Bright yellow-brown, paler muzzle and elytral margins. A wide black vitta on each elytron. Antennal segments 1-4 pale. Last 2 segments of tarsi black. Abdominal segments 1-4 with sides black. Cairns, 9mm. = polita.
    *Elytra finely shagreened and subopaque. = 11.

11. Elytral vittae distinctly widening posteriorly, each vitta begins well past the elytral base. Tarsi and parts of tibiae dark. Antennal segment 4 slightly longer than 3 or 5. Coen, 7.5-10mm. = variivitta.
    *Elytral vittae scarcely, if at all, dilated posteriorly. Vitta (may have a faint purple gloss) begins near elytral base and ends near apex where it curves (may look like a large U). Tarsi scarcely darkened. Antennal segments 1-2 pale, 3-6 with dark areas, 7-11 all dark, segments 3,4 equal length. NT, 6.4-7.9mm. = silphomorphoides.