While relaxing in a lawn chair and watching my hives yesterday afternoon, I noticed two Carpenter Bees swooping back and forth in front of one hive. It appeared that they were attempting to snatch a honey bee out of the air. Then, one of the CBs landed in the entrance of the hive for a moment and grabbed a honey bee and took off!
The honey bees did not alarm while the CB was on the entrance. The second CB noticed the first with the captured honey bee and tried to take it away. Both fell on the ground where I squashed them, including the honey bee -- so I know that I was not seeing things.
I can not find where this behavior has been noted in the literature. It was certainly clear that the CBs were hunting. The fact that Bald Faced Wasps hunt for honey bees is well known, but the CBs was news to me. So, beware: Keep an old badminton racket near your hive to wack these nassty preditors.