There are many families to which this clearly does not belong: Geometridae, Sphingidae, Noctuidae, Lymantriinae, Limacodidae, to name a few. The dorsal wart behind the thorax suggests Lasiocampidae. Please rear it in captivity to get an adult moth so that we can discover its species.
If they on a plant: feed them that. If they are wandering around, they are probably seeking some where nice to pupate, so do not need feeding. If they look little and wandering, try one leaf each of their 5 major food groups: Grass, Gum, Wattle, Herbaceous, and Lichen, and continue with their choice. If all else fails, try Rose petals (available from many florists).