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HOW COME? Insects caught forever, in amber

How can insects be preserved in amber? asks a reader.Think "fossil," and you probably imagine an animal's shell, bones, or teeth, recreated in rock. But in fossilized amber, we often find a tiny animal's actual body, from eyes to wings to antennae, perfectly preserved.

Amber allows us to see with our own eyes what ancient, now-extinct life actually looked like (such as a praying mantis, trapped 87 million years ago in Japan).

How does it work? Amber is fossilized resin, which once oozed from the bark of a living tree. Picture an insect crawling on the trunk of a tree, only to get caught in a glob of sticky resin. Centuries pass; the tree dies and decays, but the chunk of dried resin hardens. Sediment covers it, and over time, buries the resin inside the Earth.

Over time, many animals and plants disappear -- including the insect's own species, vanished into the dust of Earth. Meanwhile, the resin hardens into a fossil. Sediments carrying the fossilized resin are gradually pushed up by the movements of land masses. And one day, scientists, digging for fossils, find a chunk of smooth, translucent amber. Inside, the insect waits, held in its golden prison for millions of years.

Scientists have even unearthed amber containing thousands of long-extinct ants. But insects aren't the only things imprisoned by amber. Tiny frogs, hair and feathers, fruit and tree leaves, spider webs, bacteria, and other remnants of the ancient Earth have been found.

So far, the oldest creatures found in amber are two tiny mites, discovered in Italy. The mites lived around 230 million years ago, when most of Earth's land was united in one vast supercontinent (Pangaea). Scientists speculate that the mites may have unknowingly engineered their own end, by feeding on a tree and releasing its gluey resin.

And sometimes, amber preserves a scene from the past. Spring flowers, bursting into bloom. A brood of baby spiders, emerging from a white cocoon. And, in one of the most startling amber images, a predator about to pounce on its prey.

The fossil was found buried in a mine in Myanmar (the nation formally known as Burma). It shows a small male wasp, caught in a spider web. Looming above it is a young orb-weaver spider. The wasp appears to be staring at the spider, about to make him lunch. Nearby, a second spider lurks in the web. But before the spider could make its move, all were caught in a flow of tree resin -- and frozen forever. Researchers say the confrontation took place between 97 million and 110 million years ago, when dinosaurs roamed the planet.

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