How do you rear Cockchafer beetles?

Very difficult; the larvae which live under ground for a year or more eat live roots. The chafer which emerges eats many soft green leaves but dies after a couple of weeks. I think rearing cockchafer beetles is not practical.

You can however try other related beetles, like Eudicella smithi bertherandi (look it up in wikipedia: http://nl.wikipedia.org/wiki/Eudicella_smithi ) which eats bananas, and the larvae eat rotting deciduous leaves in an advanced state of decomposition. You still have to have a lot of patience, though.