Overview

All living beings in an ecosystem are vital parts of it. Their functions bring balance, no matter how destructive it may seem. The ants are a clear example of collaboration and support of an ecosystem: they work together to get enough food and shelter for all of them. But some species of ants are not as harmless as those in our garden. Army ants are peculiar insects that evolved from an ancestor 35 million years ago. One specimen was fossilized in amber and stored in a drawer for almost a century. However, that was until mid-November 2022, when a researcher found and set out to study it.

The science and other stuff to know

Army ants are insects like no other. For example, they move in large colonies and migrate stationary. Moreover, their queen lays a million eggs per day in the settlement stage, and in the migratory stage, they move in search of food for the larvae. Depending on the species, they can measure up to 1.5cm (0.59 inches) and have sharp jaws that inflict painful bites on their victims. They feed mainly on smaller insects, including other ants, and larger prey consumed in groups.

Experts from the New Jersey Institute of Technology and Colorado State University conducted research using a fossilized army ant inside a piece of amber. The specimen dates from the Eocene, more than 35 million years ago, and is the oldest documented. Still, it was found around 1930 in an excavation and kept in the Museum of Comparative Zoology at Harvard University until Ph.D. student Christine Sosiak found it by chance.

“The museum houses hundreds of drawers full of insect fossils, but I came across a small specimen labeled as a common type of ant while she was collecting data for another project. Once I put the ant under the microscope, I immediately realized the label wasn’t accurate … I thought this is [really] different,” Sosiak said in a news release.

In her article published in Biology Letters, Sosiak and her colleagues state that this 3-millimeter specimen belongs to Dissimulodorylus perseus and is an extinct ancestor of army ants in today’s Asia and Africa.

So what?

The amber fossilization that characterizes this found specimen arises from the resin of an ancestral tree species. Due to their physiology, experts deduce that this type of ant mainly lived underground, so it is doubtful that many specimens have been fossilized. That’s why this discovery is unique and will provide biologists with new knowledge about the evolution of army ants and their migratory behavior 35 million years ago.

What’s next?

The researchers conclude the study by highlighting the importance of correct categorization and in-depth analysis of the fossil pieces found in future excavations. Unfortunately, an oversight of almost a century caused an ancient piece of incalculable value to have been forgotten. They also suggest that the “amberization” of these insects should be further studied to complete the models of the biological evolution of army ants.