Serendipitous discovery gives biologist delight

SUN JOURNAL

Research: A Canadian scientist spotted a butterfly with ears in a tray of specimens, a discovery that took her to an island where chance intervened again to let her find the insect in question.

May 20, 2000|By Bryn Nelson | Bryn Nelson,NEWSDAY

Jayne Yack's revelation came in the dim light of an old pump house on an island in Panama, in the form of seven pairs of softly fluttering wings.

Coincidence, she says, happens all the time in science. You just have to know what you're looking for.

Yack had been looking for something else when she first discovered a pair of ears on the wings of a small nocturnal butterfly. That discovery twice led her to Panama, where she was determined to study the creatures in the wild and test her hunch about the purpose of those delicate ears.

Now, as the butterflies began to fly in their characteristic slow, graceful manner, Yack used a hand-held device to emit a single burst of 25 kilohertz of sound, or 25,000 vibrations per second.

Such ultrasonic frequencies are well beyond the human range of hearing, but the butterflies reacted immediately by undertaking a series of loops, dives or a movement Yack compares to the motion of a washing machine. She didn't need to study her camcorder videotape to know what was going on."This behavior," she says, "we know is classic bat-avoidance behavior."

Ultrasonic hearing isn't unusual in the nocturnal insect world. Other research groups have found ear organs in insects such as praying mantises, green lacewings, grasshoppers, katydids and certain scarab beetles. But Yack's discovery marks the first time such ears have been unambiguously identified in butterflies and linked to their bat-evasion efforts.

Her study offers a new glimpse into the evolutionary race between bats and their prey and a new take on the relationship between moths and butterflies. In addition, she proposes a new theory: Bats may have spurred the evolution of some butterflies by forcing them into the daylight hours to avoid being eaten at night.

Six months before her triumph in Panama, Yack had been browsing through trays of butterfly and moth specimens at the Canadian National Collection of Insects, Arachnids, and Nematodes in Ottawa, Ontario. A behavioral biologist at Carleton University in Ottawa, Yack occasionally visited the collection for her research on moth anatomy. But that day, she found herself staring instead at a small gray and white butterfly with a pair of unusual structures on its wings.

As she peered, she remembered a paper by noted entomologist Malcolm Scoble in which he had reclassified the insect as a butterfly, a departure from conventional systems that had grouped the nocturnal creature with moths. Scoble had speculated that the structures on the wings of these insects, called by their family name, Hedyloidea, were perhaps involved in hearing or scent. Intrigued, Yack asked permission to take the specimen back to her laboratory where she could take a closer look.

"One day I started poking around and I was just blown away by seeing this amazing structure," she says. "I saw this extremely thin membrane, and I knew right away what it was." It was an eardrum, similar to the structures Yack had been studying on moths for a decade. Only this was the first time such ears had been identified in butterflies - on the wings, no less.

Yack quickly made plans to travel to Panama to study the creatures in their native habitat. Her only clue to help her locate the butterflies and their caterpillar larvae was the identity of a plant favored as food by a single species.

"I was looking for this plant," she says, "and apparently it had all been chopped down and an invasive plant had taken its place." Yack found no sign of the caterpillars or the butterflies. On the final day of her stay, she went to Panama's Barro Colorado Island, a nature monument and center for biological research maintained by the Smithsonian Institution.

Before heading back to Ottawa, she was able to collect a few butterflies to begin a study of their anatomy.

Three months later, she returned to the island for a second attempt. She set up a black light - similar to those used in discotheques - with a white sheet draped behind it to reflect the light. The contraption often attracts a bounty of insects, and Yack was hoping that her Hedyloidea butterflies would be among them.

Nearby, an old pump house emitted a weak light that illuminated one of the footpaths on the island. Thinking that the light could disrupt Yack's collection efforts, a local guide called her over to point out the complicated light switch and instruct her how to turn it off.

Yack looked up and there, on the ceiling, were her butterflies.

"I think I kind of squealed with delight," she says. "It was one of the special, exciting moments in my life."

The old pump house provided an ideal setting to observe the butterflies' natural flight patterns. Yack would aim a quick burst of ultrasonic sound and then videotape the butterflies' loops, dives, unpredictable changes in direction and increases in speed of up to 400 percent. Together with collaborator James Fullard, a professor of zoology at the University of Toronto at Mississauga, Yack recently published her results in the journal Nature.

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