I don't think it's a bee. Bees only forage for pollen and nectar. This looks like slugs, worms or caterpillars. Many of them are nocturnal and/or camouflage so well, you can't see them though they are right in front of you. This is why I always keep a bird bath out full of fresh clean water plus a few treats for my feathered friends. They take care of problems like this.

Earwigs are the usual culprits with flowers, and they operate at night - time to get the torch out and sneak out for a peek after dark. The only thing is, some of those 'bites' appear to be semi circular, the sort of shape a leaf cutter bee leaves behind - but it'd have to be a daft bee trying to use part of a flower petal to roll around its eggs - they usually choose leaves like rose leaves.

The leaf cutter bees use flowers all the time, here in Phoenix, though this is the first time that I have seen a Hollyhock as a victim.