http://www.nytimes.com/2006/04/04/science/04ant.html

The ants' hang time was impressive not because their bodies were particularly aerodynamic, but because they knew how to move their long limbs around to reduce drag. They moved their left hind legs outward and rotated them, an off-kilter motion that allowed them to maintain altitude.

"Any object can generate lift if it's asymmetric to the air stream," Dr. Dudley said. "If you put your hand out the window of a car and rotate it, you'll feel it being lifted. Hands aren't that aerodynamic, and neither are the ants, but you'll get this effect just the same." The legs' increased distance from the ants' center of mass also creates torque, spinning their bodies around — and accounting for the spectacular swerves they often display before coming in for a landing.