How did it go? I just drop one in an empty cup if it looks mature, I would think oats as substrate might stop them from pupating since they can't form a cell. One can pupate in two weeks if it is in a circle shape when you find it, but usually much longer.
All went well. I've pupated over 10 beetles on oats with a 100% success rate! I even found one in the larvae enclosure (filled with old isopod substrate) and it pupated on the top, proving that they do not make pupal cells.
Well they definitely DO make pupal cells if they have compressed humid substrate... however in a communal setups their siblings usually collapse their pupal cells, and through their digging activities the pre-pupal larvae are pushed up to the surface. So you'd need to isolate them to observe true pupal cell formation.
