Types of Wood for Beetle Substrate

[The Mantis Menagerie]

I have been having a hard time getting oak sawdust for fermenting into substrate for beetle larvae, and I was wondering if other types of wood would work. For example, I can get finely ground aspen at my local pet store, but I don't want to end up killing my beetles due to improper substrate. I currently have 10 Lucanus elaphus larvae that I have been feeding rotten wood and I have been hunting for the native Dynastes sp.

I am planning on trying to make beetle kinshi, and I was wondering if any media can be used to grow the mycelium besides oak sawdust (such as aspen) without any adverse affects to the beetle larvae.