whilst walking past a eucalyptus tree whilst on holiday in Queensland, Australia, my ear and side of head just brushed a leaf and I received a stinging sensation. On returning to investigate I found what I believe to be the culprit and have attached a photo. Be interested if this is a common bug.
Your caterpillar bears an uncanny resemblance to a North American species known as the Saddleback Caterpillar, Sibine stimulea, except for the coloration. We suspect it is a close relative, one of the Slug Caterpillars in the family Limacodidae, many of which have stinging spines.
The Stinging Slug Caterpillar is a Mottled Cup Moth, Doratifera vulnerans, found throughout Australia. They eat the foliage of Eucalypts, Melaleuca and sometimes exotics. The Moth is brown and hairy.