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Amber Fossil Shows ‘Hell Ant’ Was Unlike Anything Alive Today

The 99-million-year-old ant had scythe-like jaws that swung upward to pin prey against a horn-like head appendage

A 99-million-year-old piece of amber trapped this worker hell ant grasping an ancient relative of modern cockroaches in its unique jaws, which swung upwards unlike all modern ants. (NJIT, Chinese Academy of Sciences and University of Rennes, France)
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Some 99 million years ago an ant unlike any alive today was in the midst of a savage scythe-jawed attack when dripping plant resin froze the insect, along with its prey, in a final predatory tableau.

Now, new research based on this amber-tinted window into the Cretaceous confirms that so-called “hell ants” made a killing with the help of recurved mandibles that swung upward, pinning or even impaling prey against a horn-like protrusion sticking out of its forehead, reports Lucy Hicks for Science.

"Hell ants have two features found in no living species: highly specialized scythe-like mandibles and a wide diversity of horns that are present on what is essentially the forehead," Phillip Barden, a paleontologist at the New Jersey Institute of Technology and lead author of the paper, tells Katie Hunt of CNN.

Paleontologists have long suspected that unique mouthparts of the 16 known species of hell ant hinged shut vertically, rather than horizontally as is the case in all living ant species. But the newly described specimen is the first hard evidence that this is indeed how these early ants sharp jaws functioned, the researchers report this week in the journal Current Biology.

"The only way for prey to be captured in such an arrangement is for the ant mouthparts to move up and downward in a direction unlike that of all living ants and nearly all insects," Barden says in a statement.

Ant evolution
A graphic representing the evolution of hell ants and modern ants with illustrations of their different mouth parts. (NJIT, Chinese Academy of Sciences and University of Rennes, France)

The hunk of amber containing this ancient drama was first unearthed in 2017 in Myanmar. The region has produced a trove of mind blowing fossils but armed conflict has tied the amber trade to horrifying human rights violations, leading many to avoid dealing with fossils from the region, as Joshua Sokol reported for Science in 2019. The authors of the current research note that the fossil originated in Myanmar’s Kachin State but was “deposited in the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences prior to the 2017 military control of some mine regions...All authors declare that the fossil reported in this study was not involved in armed conflict and ethnic strife in Myanmar.”

The particular hell ant locked inside this fossilized amber is Ceratomyrmex ellenbergeri and its prey, which has its head smashed between the ant’s jaws, is a cockroach-relative called Caputoraptor elegans.

"Once the prey was gripped in this way, the ant most probably moved on to an immobilizing sting—we know that the stings of hell ants were well developed," Barden tells Hannah Osborne of Newsweek.

Speaking with Mindy Weisberger of Live Science, Barden hypothesizes the gruesome fate that may have awaited the cockroach nymph after being paralyzed by the ant’s sting: "They have these highly specialized mouthparts that are so exaggerated they can't feed themselves. Instead, they feed the prey to their own larvae—and the larvae have unspecialized mouthparts, so they can chew normally."

After the pale larvae have had their fill, Barden suggests the adult hell ants might make small incisions in the larvae’s’ soft bodies and drink the next generation’s blood (called hemolymph in insects). "Basically, they use their own siblings and offspring as a social digestive system," Barden tells Live Science. "We don't have direct evidence that's the case here, but that could be something that's going on."

For those alarmed by Barden’s imagination, the inspiration for this grisly scene is a living species called the Dracula ant.

Hell ants are among the earliest known ants, but what remains a mystery is why they, along with their unique jaws, died out roughly 65 million years ago after some 20 million years of roaming the planet, while the relatives of modern ants persisted and flourished.

“Over 99% of all species that have ever lived have gone extinct,” Barden says in the statement. “As our planet undergoes its sixth mass extinction event, it’s important that we work to understand extinct diversity and what might allow certain lineages to persist while others drop out. I think fossil insects are a reminder that even something as ubiquitous and familiar as ants have undergone extinction.”

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