The dotted head capsule suggests the group including Chlenias auctaria, like http://lepidoptera.butterflyhouse.com.au/naco/auctar.html although other photos of nominally that species have shown a pale green rather than pale yellow head. It would be wise always to carry a small plastic specimen bottle to take any found Lepidoptera larvae for rearing in captivity to protect them from predators, given that most Lepidoptera females lay several hundred eggs, but on average only 2 will survive to breed if the population is stable.