New pet peeve: ANTS

My ant bites may just be going away -- the bumps are small as pinpoints, the color is just a shade darker than my arm's normal pigment, and they don't itch anymore -- but I feel like the little bastards have declared war on me and my backyard. Whenever they've got the chance, given one minute or one second, the little monsters crawl up on my feet and just ... well, they just BITE me again! One little creep bit me on my big toe, another on my ankle. Just moving around a couple rocks or a stepping stone can bring on the most incredible revolt amongst them, and they get all angry, quick and agile crawling all over a bougainvillea or rock, and seem to be on a search-and-destroy mission for me alone, even though Brian may be closer to them. Some of them even hitched a ride on Oliver's fur this morning to try to infiltrate my home and get closer to me. I think I can say pretty strongly that, yes, I hate them.
This morning, we purchased a can of ant-killing Raid for the backyard. Who knows how well it will work, since the little monsters are outside, and therefore (I believe) tougher than the indoor ants. I did have the opportunity to spray the buggers on the bougainvillea, and it seemed to have been helpful. But here's my thing: why spray bugs outside? Don't they just have to go, oh, I don't know, four feet to the left or right to get back to where they want to go? They've got the whole outside, as well as the ground and under it, to make their case for being exactly where they want to be. How on earth does one defeat these awful little creatures?