Georgia Finemore, via email

I found this interesting leaf/pupa on our Corymbia ‘Summer Beauty’ tree. Can you tell me exactly what it is?

Martyn Robinson says

It is a gall formed by a tiny cynipid wasp. Several insects cause galls on plants. The insect lays its eggs in the plant tissue, and the irritation causes the tissue to swell around the eggs and hatchling larvae, which provides them with a safe place to feed and grow. You can cut them off and compost them – or leave them be, as they do little damage to the plant.