Believe it or not, but ants can be good to have around (in moderation and depending on species). The ants are attracted to, and feed on the nectar just like bees, except they are far less likely to cross pollinate (they aid in self pollination though). I use the ants to show me where the aphids are, then I manually destroy the aphids and let the lacewings, parasitic wasps, orius, and ladybugs handle the ones I miss. Luckily for me though none of the aphid utilizing ants in my area sting! Also as an entomologist I can tell you that it is a common misconception that ants "bring" the aphids onto the plants. Most of the time winged aphids seek out host plants where they "poop out" wingless clones at a ridiculous pace, later to be discovered and utilized by the foraging ants. There are exceptions of course, but MOST of these exceptions involve species of flightless "root aphids" that depend on ants to move them about underground and place them on plant roots.