The identity of the Quiz Bug is revealed below, but first:

Yes Emily, the object in the photo looks very much like a Golden Snitch. However, a Golden Snitch is approximately the size of a walnut. As stated in the caption of the photo, our Quiz Bug is about 2 cm (including the wings), considerably smaller than a walnut.

The Hints Answered:

Rainbow – Multicolored

Not Occidental – Oriental, Asian

Peeress – Noblewoman, Gentlewoman, Lady

Sheath Wing – coleoptera, beetle

With all hints put together, our bug is a Multicolored Asian Lady Beetle (Harmonia axridis), although they answer to many other names, like Harlequin, Asian, Japanese, Halloween (Sarah’s answer), or Pumpkin Ladybug, Ladybird, or Lady Beetle. They are as varied in their appearance as in the nomenclature. Some are bright red-orange while some are pale. Some have many spots while others have no spots.

Normally a ladybug’s wings (hindwings) would be folded under the elytra (forewings) when not in use. I suspect that our little friend had a run in with another insect, bird, and or maybe the edge of a shoe. Note the dented elytra.

But maybe, just maybe, the beetle was mistaken for a Golden Snitch by a miniature troop of Quiditch players and escaped damaged (the dent) but alive, making Emily’s answer at least partially correct!