Oregon State University zoology Professor George Poinar Jr. said the beetle was in the process of using a chemical defense response when an oozing flow of sap preserved its struggle for eternity.
Poinar said the discovery is the earliest fossil record of such a type of protective mechanism that is still common in the insect world and among other animal species.
"The chance of these circumstances all coming together at the exact right second was pretty slim," said Poinar, an expert on distant life forms preserved in amber. "You have a prehistoric insect being attacked, using its defenses to ward off the predator and the whole event becoming captured in action as sap flowed down a tree. It's quite remarkable."
The beetle, about one-quarter inch long, was being attacked by a larger insect, of which only an antenna was found in the amber from the early Cretaceous Period. The amber was retrieved from the Hukawng Valley in Myanmar, formerly Burma.
The research appears in the Journal of Chemical Ecology.