I found several of these inside an old palm sheath on the ground, and admittedly am making the leap that they are Allacta australiensis. Nymphs in "A Guide to the Cockroaches of Australia" by David Rentz are similar, and other examples via a google search also look similar. This is the only example of its genus in Australia, and while Rentz shows it does not occur south of the Queensland border, it mentions distribution is patchy. It is associated with specific host trees which fits, although Rentz does not mention which trees. This is the only nymph I can find which remotely matches this specimen.