On Barro Colorado Island in Panama, at the turn of the new millennium, Stephen Yanoviak had the first half of his epiphany. He was high in a rainforest tree, sharing a branch with workers of Cephalotes atratus, a large, dark, spiny, heavily armored ant. Yanoviak is an experienced and circumspect climber, but now and again, inevitably, his hand would come down on an ant. At the prick of the spines, he would brush the insect away. It would fall from the branch into the void.

Ants in his plants

Steve Yanoviak drops ants from jungle treetops for a living. Don’t you want to watch him do it?

Click here to visit his website.

And checkout an MSNBC report on Yanoviak and his research.

“I was working on a project involving the ecology and behavior of ants,” he said recently, over the office chatter of Peruvian colleagues in the jungle town of Iquitos, his base in the upper Amazon. “When I was up there, gathering data, there were long periods when there wasn’t a lot to do. I just had to sit around and watch ants eating different kinds of leaves. And like anybody who works up in high places, you get a kind of an obsession for the way things fall. And so I started dropping ants off the tree. And I noticed that some of them weren’t falling all the way to the ground.”

As a 10-year-old, in the suburbs of Philadelphia, Yanoviak was obsessed with insects, snakes, frogs, and anything else that hopped or crawled. He spent a great deal of time catching crayfish. “For as long as I can remember, I’ve liked being outside. I’ve always had a fascination for very small things and how they work and live, he says” This is common testimony from field biologists. Few can remember a pivotal episode. None can recall a time when they were not mesmerized by the natural world. The great E.O. Wilson, dean of the ant people, calls this predilection “biophilia,” and Steve Yanoviak arrived with a congenital case of it. Chronologically he is now 37, but spiritually, by his own estimate, he remains about 17. He wears a ponytail; earlier in his exploration of the tropical canopy, he climbed his trees barefoot.

N. Zegarra

Yanoviak was excited by his observation of the non-random fall of ants, but he had no funding to prolong his stay in Panama, and he was deep in what he calls “Finish Dissertation Mode.” The dissertation was on phytotelmata, “plant-held waters,” in Panama’s rainforest trees. He moved his observation on gliding ants to a back burner, where it cooled and then went cold.

Five years later, he found himself in the lowland rainforest of the Peruvian Amazon, managing the fieldwork for a National Institutes of Health virus study. Again he was investigating phytotelmata. In the tropical forest, rainwater fills hollows in trunks, branch crotches, basal leaves of bromeliads, bracts of heliconia, and the basins provided by the giant woody caps of fallen tropical nuts. Giant damselflies and poison- dart frogs hunt these microcosms, which are populated mainly by mosquito larvae. One mosquito common in the Peruvian canopy, Haemogogus janthinomys, is a vector of yellow fever. Many unsuccessful attempts have been made to breed the species in the laboratory. Yanoviak was collecting as many blood-fed females as possible to get a lab colony started. His technique was to offer the females the blood meal of himself.

One day in the forest a few kilometers outside of Iquitos, he selected a tree of the genus Parkia, which is widespread in Amazonia: a group of giant legumes, with broad, flattened crowns and big, black seedpods hanging at the ends of long peduncles. With a slingshot, Yanoviak fired a weighted fishing line over a high branch. He attached a clothesline to that leader, pulled the clothesline over the branch, and then followed the clothesline with a climbing rope. Clipping his Jumars to the rope, he ascended. One hundred feet above the ground, he reached his destination branch, which was pale, smoothbarked, and about 18 inches in diameter. He was immediately greeted by the residents.

“I ran into a colony of these same ants, Cephalotes atratus. This time they attacked me. They nest in hollow living branches of the tree, and I guess I was sitting right on top of their nest. Hundreds of them were running all over me and all over the branch I was sitting on. They don’t sting, but they gnaw on you, and they become more or less unbearable. Basically I tried to give myself an ant-free place on the branch to put my hand down. I brushed a bunch of ants off, and watched them fall.”

Several meters below the branch, the falling ants became a squadron and glided back into the trunk of the tree.

Yanoviak was transfixed. He instantly remembered the gliding ants of Panama. No one, to his knowledge, had ever written about wingless flight in insects. Here in Peru, with this second heavy hint from the tropical forest, he realized that he might be onto something.

Returning to the tree the next afternoon, he began painting the ants with white nail polish. He daubed the polish on different parts of the ants, so as to clarify whether they were falling belly up or belly down, head-first or tail-first. He dropped his subjects and videotaped them with a small digital camera.

“The second big epiphany for this project was when I saw white-painted ants walking past me on the same branches they were dropped from, a few minutes later. They were doing this on purpose. They were trying to get back home.”

As Yanoviak’s nail-polished ants, Cephalotes atratus maybellinus, marched by him on the branch he fell in behind, figuratively. The ants changed the direction of his career and they opened a new field of science: the study of flight in wingless arthropods.

He just sits for hours up in the tree,” mused Professor Robert Dudley, reflecting on Yanoviak. Dudley teaches at the Department of Integrative Biology at Berkeley, where he specializes in biomechanics and the evolution of animal flight. “That’s why he’s seeing a lot more than most people. Orangutans swinging by, everyone notices that, but Steve has got an eye for subtle things. He’s a classical sort of field naturalist. He’s at home in the canopy, very comfortable there.” Dudley paused. “But it’s hard to do it forever,” added the professor, who was trying to lure his young colleague down from the treetops. “We’re trying to get him here, as a threeyear post-doc.”

Dudley, himself afflicted by scientific wanderlust, chronic and irremediable, does his fieldwork at all latitudes and altitudes, yet one place he finds himself returning again and again is Barro Colorado Island, where Steve Yanoviak had his first brush with airborne ants. Dudley first heard of Yanoviak’s ants there. After his second brush with the ants in Peru, Yanoviak conferred with an ant-ecologist colleague, Michael Kaspari, who suggested a collaboration with Dudley.

“Me, Mike Kaspari, and Steve Yanoviak, we were just hanging out in Panama,” Dudley said, sitting in his office in Berkeley. “Mike said, ‘What do you know about gliding ants?’ I thought he was joking. There’s no such thing. But then I talked with Steve and I thought, ‘This is the most exciting thing since sliced bread.’ We decided to start working on it as soon as possible. It has huge implications for the evolutionary origins of flight in insects.”

The three men did their first joint fieldwork in Peru. In the treetops outside of Iquitos, they shanghaied workers of Cephalotes atratus and dolled them up with white nail polish. Gripping the ants in mid-thorax with forceps, they held them a few centimeters to the side of the branch, and dropped them, one after another. Each fall came in three distinct stages: first a vertical plunge, second a rapid directional adjustment and body alignment towards the tree, and third a steep but directed glide to the trunk. The flight path was J-shaped. Eighty-five percent of the ants never reached ground. By painting the gaster (the final body section) and hind legs white, the researchers determined that in the adjustment phase, the ants align their abdomens toward the trunk and sail in toward it, topside-up and tail-first. This was the first record of any macroscopic animal gliding backwards on purpose.

“We don’t have many examples of backward locomotion,” said Dudley. “Some eels go backward. But it’s just not out there as a concept. Backwards locomotion. We are certainly not designed for it.” Dudley smiled one of his fleeting smiles. The professor is a trim man, 45, with semi-curly hair of indeterminate color and features just beginning to weather from a life in the field. He speaks rapidly, trying to keep pace with his thoughts, and sometimes the words run together.

“The ants glide in abdomen-first with their legs outstretched. Clearly, they’re kind of doing what skydivers are doing—slight postural rotations.” Sometimes the ant glides in to the near side of the tree, other times it sails around to the backside. Occasionally an ant will head—or tail, actually—toward a brightly lit patch of leaves, then realize its mistake, execute a sudden 180-degree turn, and glide back toward the pallor of the trunk. If spooked by a foreign object, an ant will voluntarily drop from the branch, casting its fate to the wind. Ten minutes later, it is back up on its branch.

The three researchers suspected that visual cues were guiding Cephalotes workers in their sail back to the trunks. To test this, they blinded ants by painting their eyes over with white enamel paint. These specimens, as expected, fared poorly. They then set out to identify the precise cues. From the railing of the canopy, they unfurled five velvet sheets, each one narrow and 10 meters long—an abstraction of a tree trunk—and each in a different color: red, black, blue, yellow, and white. In one experiment, they substituted green for blue, and in others they tried shades of gray. It was a beautiful convergence of science and art. “Cristo in the rainforest,” Robert Dudley said of their rainbow curtains.

To correct for any skewing effects in the method of launching of the ants, the team dropped the insects in different ways. In the Long John Silver Method, the ant was made to walk the plank—a stick projecting from the railing above the hanging sheets—its retreat discouraged by a barrier of toothpaste.

As predicted, the ants showed a strong preference for gliding toward white sheets, and after that, toward the lighter shades of gray, like the lichen-covered bark of rainforest trees. The red sheet performed poorly. It seems that Cephalotes atratus, like most insects, cannot see red.

“You don’t need wings in order to fly,” Dudley summarized. “Ants are derivative. They are very recent, relative to other insects—they don’t turn up until the Cretaceous—so they’re not the missing link, or anything. They just demonstrate feasibility. Or plausibility. It looks as if in insect evolution, controlled aerial behavior precedes the origin of wings.”

The evolutionary implications are important, and Yanoviak and friends have given us a new fable, besides. As a rule, the parable of the social insects is told as a cautionary tale: The hive, the nest, the termite mound are evoked as warnings about the direction human society is headed. So it is cheering to learn that individual workers of Cephalotes atratus are not, after all, just expendable cogs in the machine. Their lives are regimented, surely, but not entirely bleak and Orwellian.

“Ant workers, even though they’re reproductively sterile, are valuable,” said Dudley. “There’s something clever going on.”

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