I have never seen Lithosiini larvae behaving in such a communal manner. Maybe they do? While these are an early instar they are not newly hatched which is when many caterpillars are more communal. It is Thaumetopoeinae incl. Epicoma sp that have this communal behaviour.
I have found mature Asura and Hectobrocha larva living communally. Many Epicoma species larvae have a white 'face' which these do not have, but these could be Ochrogaster lunifer or one of the many species for which no larval photos have been published. Moth larvae are just a big lacuna in Australian ecology.