After searching the web, this is my best guess as to what kind of ants they are.
Larger Yellow Ants, Acanthomyops interjectus, commonly called Citronella Ants
Description: These ants give off a pleasant citronella or lemon smell when crushed. Yellow ants are yellowish to reddish brown; workers are about 3/16 inch long. Workers are usually not seen by home dwellers. Yellow ants are more commonly noticed when the winged forms are swarming. Queens are about 5/16 inch long and often reddish and darker. Yellow ants have the following characteristics: 1) petiole with one node, 2) thorax is uneven in profile (workers only), and 3) compound eye is small in proportion to head.
Foods: Honeydew, rarely other sweets.
Nesting Sites: In soil under stones, logs, bricks, patio blocks, concrete and other concealed areas. They also can nest in rotting wood. Yellow ants can nest in and around foundation walls and in soil under buildings on slab construction. Workers may be seen throwing out dirt or cement particles, but they do not damage masonry or wood.
Mating Swarms: April through August. Swarms are also common during winter if ants are nesting under heated concrete slabs.
Best Pest Management Methods: Control winged yellow ants by physical means, e.g. with a vacuum, or by hand. Large numbers can be controlled with an application of an insecticide that is labelled for flying insects, such as pyrethrins; Detection of yellow ants nesting under concrete slabs is difficult and control is rarely practical or justified.
I found information on several sites, and they all say that these ants are harmless. They do no damage and do not normally enter homes like those nasty little black ants do. If it were me, I'd just leave them alone and they'll go away.
[i]Edited to add that you might want to make sure your neighbors aren't watching when you go out to your patio to sniff the ants. I know you're gonna do that now...come on...admit it...you can't resist the urge to see if they really do smell lemony. And let us know how it turns out.[/i] [;)]