Robber flies are strong predators that snatch their prey on-the-fly, then suck them dry; they stab the hapless creature with a proboscis that injects saliva to paralyse and liquefy, turning a fully functioning bee into a kind of slushy machine. If that sounds good to you, you can read more about them on Wikipedia.
I spotted this handsome specimen of the Asilidae fly family on a post in the garden this morning, bee firmly grasped in its powerful front legs. It stayed completely still while I fetched my camera from inside, and then proceeded to get in very close to take these shots. Most obliging, it was. Either that, or the logistics of trying to get away while your proboscis is inserted up to the hilt in a bee’s liquefied insides prevents a rapid retreat.