Breeding urchin beetle(Prionotheca coronata)

[Hisserdude]

In fact, I could not prepare that soil because I did not know what the final instar was.
The larvae have turned into prepupae on silica sand.
It may have been a good idea to keep them completely dry from prepupa to just before emergence .

Have you had any success rearing multiple adults? What was the setup for getting larvae to pupate?