An unusual breed of Asian snakes can glide long distances in the air, and the Department of Defense is funding research at Virginia Tech to find out why.

Most animals that glide do so with fixed wings or a wing-like part. But not the "flying snakes" of Southeast Asia, India and southern China - at least five members of the genus Chrysopelea.

As video of the reptiles show, they undulate from side to side, in almost an air-slithering, to create an aerodynamic system. It allows them to travel from the top of the biggest trees in the region (almost 200 feet high) to a spot about 780 feet away from the tree's trunk.

(Video of an Asian flying snake taking to the air.)

"Basically . . .they become one long wing," said John Socha, the Virginia Tech researcher who has traveled extensively in Asia to study the snakes and to film them.

"The snake is very active in the air, and you can kind of envision it as having multiple segments that become multiple wings," he said. "The leading edge becomes the trailer and then the trailer become the leading edge."

It gets stranger. During a technique not yet understood, some of the snakes can actually turn in air. What's more, they all take a flying leap off their perch to get airborne, then drop for a while to pick up speed before starting the motion that keeps them aloft much longer than they would otherwise.

Socha's initial research was sponsored by the National Geographic Society, but his most recent work and paper were funded by the Defense Advanced Research Projects Agency. The agency is involved in advanced military technologies of all kinds, and Socha said the physical dynamics of snake flight (and how other creatures stay in the air) is of great interest to the agency.

DARPA did not respond to an e-mail asking for more information. However, Socha's upcoming paper on the dynamics of gliding snakes in the journal Bioinspiration and Biomimetics does list DARPA as its financial sponsor.

Socha was a featured speaker Monday at the annual meeting of the American Physical Society Division of Fluid Dynamics.

The snakes, Socha said, spend most of their lives in the trees. They are between 2 and 3 feet long and about as wide as a finger. The larger snakes, he said, generally cannot glide as far as the smaller ones.

The snakes are mildly venomous, he said, but "won't hurt a human, though they can be fatal to a gecko."

While the prospect of a flying snake seems strange today, current scientific theory says that birds evolved from dinosaurs, which were reptiles.