these gum trees were not looking too well. But they did have these all up the trunk to about 3M. Borers? what are borers? some kind of grub of a moth? not sure!
Let me 1st say I am not an expert. The best know woodboring beetles (larva) are longhorn beetles (Cerambycidae). There are others. One distinguishing feature is what part of the tree they bore in - heartwood, bark. Or if they bore in dead/fallen/cut wood. Your borers appear to be living in the surface of the bark. There are various wood borer larvae (non-native) that scare house/furniture owners - a particularly entertaining one is the Death Watch Beetle (websearch it) the other alarming one is Lynctis beetle (subfamily Lyctinae). Sadly by looking at these we will be haunted by ads from pest controllers - IGNORE THEM ... only look at scientific sites for information! Hopefully someone with better knowledge can isentify if they are beetle, moth or other larvae.
@KylieWaldon : can you start lightly lifting bark and see if you can find any live larvae underneath, that you could take into protective custody to rear to get an adult?
In these cases the outer bark was missing. These tracks were in the ?heartwood. There was nothing to lift up. THe tracks were very hard. They went from about 1M off the ground up to about 3M off the ground - but no further. I don't know if that helps or not. <3
That is still the bark or adjacent layer. Heartwood is the wood at the centre of a cross section of a tree/branch. I believe there are borers adapted to live in all the layers of a living or dead tree/plant. search (without quotes) " layers of a tree diagram australia "
do a picture search on " Cerambycidae larval tunnels " to see what these beetle larvae and some tunnels look like