I have a frequent "mugging" problem with yellowjackets around my hive.
They not only scoop up any dead bodies that fall nearby, but they tend to
hop on any incoming workers that seem sluggish or land too far from the
hive.  Yellowjackets, being carnivores for the most part, love bees as a
food source.  Strong colonies drive them off, but weak bees and stragglers
beware!
 
Jane B.