About 315 million years ago, an insect landed on a muddy patch, sat for a while and flew off.

Amazingly, that bug’s muddy impression, about 1.5 inches long, hardened and survived to today.

“It left a perfect copy of its body,” said Richard J. Knecht, a curatorial assistant at the Museum of Comparative Zoology at Harvard, who uncovered the fossil in sandstone rocks in southeastern Massachusetts. “Essentially everything but the wings.”