This looks like the rhinoceros beetle Xylotrupes australicus: https://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:afd.taxon:c8482685-310f-49db-bdf7-c0636a3ccbe5
That’s awesome Jane. It would be cool to also report the tree and get it ID’d by a moderator so we can establish the link between these guys and your beetle magnet tree!
I've corrected the name to Xylotrupes ulysses australicus after advice from entomologist Kim Pullen. He said: "I checked in AFD at https://biodiversity.org.au/afd/taxa/Xylotrupes/complete. The current name is Xylotrupes ulysses australicus, indicating that what was previously called Xylotrupes australicus is now considered a subspecies of X. ulysses." I've also added Xylotrupes australicus as a synonym.