Scientists have discovered a fossil of 52-million-year old beetle that lived together with ants and also fed on ant eggs.

The Eocene-era beetle fossil, which is called Protoclaviger trichodens, was discovered at Tadkeshwar lignite mine in Gujarat, India, by a group of scientists from the Birbal Sahni Institute of Paleobotany, Lucknow, and the American Museum of Natural History. The beetle was found enclosed in a portion of amber. The beetle is believed to be the oldest species showing social parasitism. The species is very likely to be myrmecophile, whose survival depends on ants.

The population of these beetles flourished at a time when the population of ants on Earth was on the rise.

"Although ants are an integral part of most terrestrial ecosystems today, at the time that this beetle was walking the Earth, ants were just beginning to take off, and these beetles were right there inside the ant colonies, deceiving them and exploiting them," says Joseph Parker, a research associate at the American Museum of Natural History and postdoctoral researcher at Columbia University.

The research sheds light on the beetles as well as on the ant nest, which was big enough and rich with resources to feed such beetles.

The scientists explain that ants usually have a complex security system in their nests. Intruders are usually attacked very swiftly by the ant army and consumed. However, these beetles would bypass the security system of ant colonies and lived there by utilizing their resources.

The beetles cover their body with an oily secretion that makes the ants adapt to them rather than attacking them. The scientists are unsure about the chemical composition of the oily secretion and how the beetles managed to live in ant colonies without being attacked.

Living in the ant colonies brings about many benefits to the beetles, which adapted to make the transition. They got protection from predators and fed on ant eggs. Scientists also revealed that ants provide liquid food to these beetles directly in their mouth.

Parker and his team said there are around 370 defined species of beetles that belongs to Clavigeritae, a group of myrmecophilous, which are around 1 to 3 millimeters in length. Some of these beetle species are still to be discovered by scientists. Clavigeritae beetles are rare in the wild and the latest discovery is the first fossil specimen found for this category of beetles.

The study has been published in the journal Current Biology.