swarm over (someone or something)
To crawl or gather on top of someone or something in great numbers. Players from both teams swarmed over the ball after the quarterback's fumble. All you could see was rats swarming over the pile of garbage. Mosquitos swarmed over us at the picnic, until eventually we had to pack up and leave.
swarm (all) over someone or something
to gather and move all about on someone or throughout something or some place. The ants swarmed all over our picnic table. The children swarmed over the furniture.