[cypher]

I know it does make you feel a bit nervous about putting your hand in the cage if they've bitten before but I suspect the only reason he bit before was because you put a fist in the cage which is kind of like presenting them with a big chew! There's not much they're likely to do other than sniff it & have a taste
If you try putting your hand flat as I suggested before & just bury the tips of your fingers in the substrate with a nice treat on your palm he will most likely just want to investigate the treat.