To the uninitiated, it looks like two small specks. But to paleozo-ologist Conrad Labandeira and colleagues, the fossil of a pop-eyed bug represents the oldest insect known, dating back some 390 million years.

Their findings, reported in Friday's issue of the journal Science, describe the remarkably well-preserved fragments of a wingless bug found in a chunk of mud on the north shore of Quebec's Gaspe Bay. A member of the most primitive order of insects, it was similar to modern-day silverfish.Even more significant than the fossil's age, scientists say, is that similarity to modern bugs, suggesting that insects originated many millions of years before the specimen lived.

"What we have is two fragments. We have a head capsule 0.7 millimeters wide, and we have a thorax 1 millimeter long," Laban-deira, a 38-year-old graduate student at the University of Chicago, said Friday.

"Even though they're separate, we're very convinced that they belong to the same individual," he said.

Insects are a class of animals characterized, as adults, by a body divided into head, thorax and abdomen, three pairs of legs on the thorax, and usually two pairs of membranous wings.

The prehistoric bug described in Science was found by Francis Hueber, a noted Smithsonian Institution paleobotanist who retrieved the specimen about five years ago while examining a mud sample he had found on the Gaspe Peninsula.

Its importance was only recently discovered when he and other scientists compared notes.

Hueber's interest was in prehistoric plant fragments in the dirt, but what looked like ancient insect parts caught his eye.

"He had an idea that there was something very important" about the fragments, Labandeira said.

The bug lived 390 million to 392 million years ago and predates what was previously believed to be the oldest insect _ an eye fragment found in upstate New York _ by about 15 million years, they said.

Its most imposing features were its two disproportionately large eyes on each side of its head. It also had two antennae and two armlike appendages that appear to have been equipped with sensors to detect odors and vibrations.

"The exciting thing to me is that these insects have changed very little as far as we know in almost 400 million years," he said. "That suggests that they were almost already modern in form 400 million years ago, that they had a long history before that.'