Ants on hibiscus?

Hi,
I don't know all that much about hibiscus but have several in my yard that are just beautiful. I have 3 standard (tree shaped) and I just bought these cool "dwarf" looking hibiscus from Home Depot. (They weren't labeled as dwarf, but they are very small, low growing and in full bloom. About the size of impatiens). Anyways, I've noticed ants crawling into the small hibiscus flower and up the trunk of the tree hibiscus.

Are ants harmful? I know something's been eating the leaves on one of my tree hibiscus (which touches a hedge) but I think it looks more like caterpillers even though I haven't seen any.
What about the ants?

Thanks,
Kim

Kim, usually if you have ants, you have aphids, which leave behind a sticky syrup....Hibiscus are notorious for getting aphids, especially around the blossoms. If you have just a few smaller plants, you can get one of the pesticide/fungal combinations from WalMart, Lowes, or Home Depot that come in a hand pump size like a bottle of windex. You'll have to spray them throughout the summer to keep on top of the situation, we just have that kind of weather that allows them to go on and on.