Ants and aphids on grape leaf.

Trying to figure out what's happening hear. Ants have congregated on 3 stems/leaves near top of grape vine. No where else. Not sure if the ants are eating the aphids, or? Anyone else seen something similar??

[Kerry McCarthy]

Can't offer any insight but nice find.

[Danette Thompson]

I think I remember that the aphids put out a substance that the ants like to eat.

[Valerie Chesney]

OUCH! they are big ants...

[Maggie]

Aphids usually deposit sugary secretions so would attract ants, wasps, bees etc.