52-Million-Year-Old Amber Traps Beetle That Secretly Infiltrated Ant Colonies

Scientists have uncovered the fossil of a 52-million-year old beetle that once preyed on ants, feasting on their eggs and usurping resources from within the ant nest itself. The latest finding sheds some light on some of the smaller creatures that lived millions of years ago.

The new beetle was found fossilized in amber. It probably practiced a form of social parasitism, called "myrmecophily." The beetle stealthily infiltrated ant nests and integrated seamlessly into colony life by employing a pheromone code of recognition.

"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," said Joseph Parker, lead author of the new paper, in a news release. "This tells us something not just about the beetles, but also about the ants-their ants were big enough and resource-rich enough to be worthy of exploitation by these super-specialized insects. And when ants exploded ecologically and began to dominate, these beetles exploded with them."

Today there are about 370 species belonging to Clavigeritae, which is a group of myrmecophilous, or "ant loving" beetles. Adaptations allow these beetles to bypass ant security and prey on the ants themselves. The beetles have fusions of segments within the abdomen and antennae, which are likely meant to provide addition protection from the ants, which often pick up the beetles and carry them around the nest. They also have glands that cover their bodies with oily secretions, and thick brushes of hair on top of their abdomens, called trichomes, which act as candlewicks and conduct chemical-containing secretions from nearby glands.

"Adopting this lifestyle brings lots of benefits," said Parker. "These beetles live in a climate-controlled nest that is well protected against predators, and they have access to a great deal of food, including the ants' eggs and brood, and, most remarkably, liquid food regurgitated directly into their mouths by the worker ants themselves."

The findings reveal that these beetles have been around for millions of years. It also shows a stepping stone in the pathway that led to the highly modified social parasites of today.

The findings are published in the journal Current Biology.