I’ve seen a longicorn beetle previously, but this one is different:
it looks like the sheep longicorn, Monohammus frenchi or Dihammus ovinus, according to Brisbane Insects. Update: Chris McKay at CSIRO asked one of their experts, who says its Disterna plumifera.
Sometimes longicorns have very long antennae, much longer than this one does. The pattern is said to look like the wool of sheep, hence the common name. Sounds to me like that was a long night of trying to come up with a name in the museum basement. And I am familiar with museum basements.
The larvae (grubs) bore mainly into the branches of growing eucalypts. This can cause branches to fall off, and even the death of the tree if the infestation is severe. Fancy being nibbled to death? Me neither!