Weighing barely an ounce each, the butterflies have been clocked at speeds of up to 30 miles per hour, observed as high as 12,000 feet and seen to fly 375 miles over open water. There are at least three major monarch broods in the Americas but only the largest, which lives east of the Rocky Mountains, travels such daunting distances -- farther than any other known insect species.

Seeking the secret of time and the butterfly, Dr. Reppert and his colleagues studied rhythmic molecular changes in the four brain cells that serve as the monarch's timing device. He discovered that two similar light-sensitive genes drive the clockworks. The first, common to plants and insects, is sensitive to blue light and appears to synchronize the cells to cycles of light and darkness.

The second gene "stunned" the scientists, Dr. Reppert said, because it so closely resembled one previously found only in humans and other mammals. It doesn't respond to light directly but, when triggered, makes a rising amount of protein that measures the passage of time since it was last activated.

"It functions in the butterfly clock almost identically to the way it functions in our clock," he said.

To completely decipher the biology of monarch navigation, Dr. Reppert and his collaborators at SymBio Corp. in Menlo Park, Calif., started last summer to sequence the 250 million base pairs of DNA that make up the butterfly's entire genome. "When you do something like this, you may discover a lot of genes," said company CEO Robert Feldman. "It is an iconic insect."

In small things considered is the world revealed.

(Wall Street Journal)