Wrapping a ring of 1" wide masking tape on a smooth area of the trunk with the sticky side facing outward....is sure cheap and easy. The rings can be replaced after they are full of bugs or when the stickiness has diminished.

I have killed huge fire ant mounds by using the used coffee grounds that Starbucks gives away for free. After experimenting with these used coffee grounds for 8 years, I have found all kinds of interesting uses for them. Mainly as a direct contact spray, I can take care of all the insects I have problems with, and I have 40,000 plants. I found that the coffee spray will not kill ants, but they ARE repelled by the used coffee grounds. This may take a little practice, but I take the used coffee grounds and mix them with enough water that they turn into mud. I put a thin layer of mud all over the mound, and I found out the trick is to cover another 4 inches farther than the mound because they try to tunnel out under the coffee mud. The only thing I can figure is that they refuse to dig through the coffee, and when they can't go out and feed the mound, the colony dies. One way or another, it kills the mounds. This is hard to do when you collect your own grounds, bit you can get so much at one time at Starbucks when you go at the right time of day. Sometimes, I have come away with about 60 pounds of used coffee grounds when I ask them for the bag they are filling behind the counter. On another note, try experimenting with coffee repelling ants and other insects. Like if you had a small garden, you could pour a barrier of grounds around the perimeter of the garden to keep them away. The barrier would also keep out mealy bugs, scales, aphids, and even spider mites. I never got to finish a formal experiment, but I would bet money that used coffee grounds would get rid of chinch bugs in the lawn as well.

Good suggestions. The ants are apparently not hurting the plant (or the flowers), just gathering nectar to eat. They aerate the soil, too, so there's no point in chasing them out of the peony bed -- just off of any flowers that are going inside.

About the only effective method I've ever found is to drop a large handful of sugar on the ant hill and water in thoroughly. It encourages bacterial and fungal growth, which the ants hate. However, it doesn't kill them, they just move somewhere else. Usually that's good enough for me, and I end up with ants in a location I don't care about. On the up side, ants are generally harmless and not terribly annoying (if not in the house, of course), and perform a very positive function by deeply aerating soils. My response to them is to ignore whenever possible as they don't damage the lawn or gardens in the slightest.