Predator Large black bumble bee ?

[malabarchillin]

I had a large (thumb sized) dark black and bright yellow bumble bee (?) living in a outside
water spigot for a couple of weeks. Each day I used the spigot she would get washed out with
the flow of water,dry off and fly away. I have one of my hives near my house so I can watch them regularly. For about 2 weeks now a bee like the one mentioned above darts and hovers near my hive and picks out a honey bee and chases it in circles in the yard. It will chase individual bees for maybe 30 seconds over hundreds of feet. Now I see it 'hunting' my newly split nuc. Is it trying to just run them off or what ?
When I am in a chair 5 feet from the hive it will often hover a foot from me while it is targeting a bee. It is interesting to watch, but I can not tell if it is actually killing bees.Because of its size it is easily visible in the yard, but the smaller honey bees often get lost.

[Bill W.]

Well, carpenter bees will try to rob honey from honey bees, so perhaps bumble bees will as well?

I'd guess that you have a bumble bee nest near by and the bee you are seeing coming out of your spigot is really any number of bumble bees crawling in there to get water.

Or, you have a queen bumble bee looking to set up shop in your spigot, but that doesn't seem too likely.

We have quite a few bumble bee nests around and haven't noticed any fighting.