[They don't bring them
Actually they do
So off I went to research, and much to my surprise Auk is right. They do carry the aphids around.
Take a look:
"It appears that ants aren't just opportunistically squeezing honeydew out of any old aphid colony. They are deliberately maintaining aphid herds, possibly for many seasons,
Ants shepherd their bug flocks to better pastures and shield them from rain, sometimes carrying them from one plant to another. Ants care for and protect aphids’ eggs, treating them as their own and keeping them safe inside their colonies for winter."