gumtree scale...

...dotted along the eucalpyt branches, the eggs  in various stages of hatching into nymphs which will march along the tree and lay yet more eggs!
Poor old tree doesn't stand a chance when there are huge infestations as the scale sucks the sap and produces a sugary solution after which a black mould fungus covers the leaves which turning them black.
Ants however think this is  heaven feeding on the sugars by stroking them.
The circle of life!...tiny though it may be.