The other day I was taking pictures and saw a robber fly, a predator of bees and wasps, that had caught and killed a bee and was holding it with its legs.
Robber fly sitting on an aloe leaf
As I tried to take a picture, the fly got a fright and flew right into me, dropping the bee. Sorry that I missed the shot, I picked up the dead bee and put it in the flower pot. A few minutes later, I was surprised to see that that there were lots of little flies swarming on the bee.
Looking it up, I discovered that these are called Jackal flies and they are scavengers that feed off the body juices of insects killed by other predator insects such as spiders, wasps, robber flies, mantids and assassin bugs.
I always thought that spiders and birds were the only predators of bees but it seems that even flies attack them