Possibly Lophyrotoma analis? Very pleased to find this eating Spiny Emex (Emex australis). Waiting for it to pupate now.
The W. australiana are the tiny green plants (mixed in with Azolla rubra (the red ones) and Spirodela polyrhiza (larger green ones).
Sighting and photos (c) tubul.
Field Notes - Maybe 2cm in length. Fairly flat. Observed in a tree near a pond.