The eggs of the female scribbly gum moth are laid between layers of old and new bark.

 

The larvae then burrow into the new bark and begin to feed on the sapwood. This creates the feeding trails or “scribbles”.

 

The size of the “scribbles” increases as the larvae grow. When they have reached their maximum size they emerge and crawl out to hide behind old pieces of bark. Here they make a cocoon.  In Autumn they turn into a moth.