Ask Mr. Smarty Plants

According to this article from Floridata, "Ants inhabit the blossoms - or perhaps they're shopping for nectar. At any rate if you cut trumpet vines for indoor arrangements go over them carefully to flush out any creature that may be lurking within the trumpet's depths."

Campsis radicans (Trumpet creeper) may be infested by aphids. They pierce the leaves, and subsist on the nutrients they suck out. They are very small and white, usually found on the underside of the leaves, and lay lots of eggs. If this is going on you will find a white substance that is exuded by the aphids; this may get moldy and turn black-it is referred to as "honeydew." Where do the ants come in? They are farmers, and their herds are aphids. The ants feed on the honeydew, and take it back to their nest to feed the young, as well. They will fiercely protect the aphids from predators, but they don't chew on the plant.

Another reference we saw referred to sooty mold that often gets on the flowers, which doesn't particularly hurt anything, but is unattractive. It often indicates poor air circulation and/or not enough sunlight.

Let's talk about carpenter ants. This article from University of Nebraska has pictures and an explanation on Carpenter Ant Management. In this case, your concern would not be on the damage the ants might be doing to the trumpet creeper, but what the trumpet creeper is climbing and can the ants be damaging that? In other words, if your plant is climbing up a wooden fence or house, those ants may just be using the vine for transportation into other parts of the structure, and they are very destructive.

One last word, we would suggest you read this Dave's Garden Forum on Campsis radicans, especially the negative comments. You might decide you really don't want that trumpet creeper all that much.