I think this small staphylinoid beetle is a member of the Pselaphidae, or what used to be the Pselaphidae – now reduced to a subfamily of Staphylinidae by some authors. Perhaps some knowledgeable pselaphologist can tell me yea or nay (Don Chandler suggests Eupinion sp.). Supposedly there are about 85 species of Pselaphinae known from Canada and Alaska, but this particular one once lived in subtropical rainforest in southeast Queensland.
Pselaphid beetles are interesting to me for two reasons: they tend to be tiny and some eat mites (although more seem to enjoy eating springtails). Others find them interesting because they are ant inquilines and kleptoparasites (i.e. some can trick ants into regurgitating food for them). One of their ‘common’ names is “ant-loving beetles” – although one doubts that they are a common topic of conversation. Also, this common name does tend towards confusion with ‘ant-like stone beetles’ or Scydmaenidae, a topic in the previous post.
In any case, if you would like to spend some time reading about beetles or just looking at some pictures of them – I have good news! The first issue of a brand new blog carnival is up – An Inordinate Fondness – and it is devoted to beetles.