u/An_Officeworks_Troll

INaturalist hasn’t got a clue!
Found in Eastern Melbourne, Victoria, Australia back in April (mid-autumn) on the back of a long stretch of tree sap. About one centimetre in diameter and extraordinarily flat.

Edit: cheers everyone for all the discussion in the comments! Still haven’t got a clue what it was, but there’s a lot of close matches! Thanks again, you guys are awesome :)