NANJING - Chinese scientists have found ant-like stone beetles inside a piece of Burmese amber from the mid-Cretaceous period, about 100 million years ago.

The beetles are the world's earliest known insects to eat springtails, an insect-like food resource for litter-dwelling beetles.

A paper written by a team led by researchers from Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) was published Tuesday in the British nature research journal, Scientific Reports.

Dr Cai Chenyang of NIGPAS said there were three well-preserved stone beetles fossils in the amber.

"They are the earliest known predators specialized in capturing springtails, pushing back the age of such behaviour by at least 54 million years," Cai said.

All previously known specialist predators of springtails were confined to the middle Eocene period about 40 million years ago.

He said the early beetle had an extremely large body size, 6-7 millimeters, tripling the size of similar modern beetles. It also has clubbed antenna, toothed mandibles and slender antennae that function as an antennal setal trap, similar to that of the modern ground beetle.