Hell ants have previously been found preserved in amber in Myanmar, Canada and France. Named 'hell ants’ because of their peculiar and slightly scary-looking headgear, they have scythe-like mouthparts – known as mandibles – that look a bit like upward-pointing tusks, and a 'horn’ on their heads.
Until now, the oldest hell ants were dated at 100 million years old. But a new paper in Current Biology describes an even older ant. Found in a museum collection, a fossil from northeastern Brazil has been dated at 113 million years old, meaning ants are much older, and specialised much sooner, than we thought.
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Scientists know it is a hell ant because, using a method called ‘computed tomography’ (essentially, very detailed 3D scans), it is clear that the fossilised ant has the classic hell ant headgear.
But what was this strange headgear used for?
“The most accepted hypothesis suggests that hell ants were specialised predators, which used their mandibles to grab extinct insects,” Dr Lepeco, lead author of the study, tells BBC Wildlife. “There are fossil hell ants grabbing prey with their mandibles, which supports this theory.”
However, an alternative hypothesis – and a bit less fitting with the name ‘hell ant’ – is that the ants used their headgear to carry droplets of nectar or honeydew, sugary liquids that many modern ants feed on.
Whatever the headgear was used for, it obviously provided a foraging strategy that was effective in very different environments. In northeastern Brazil, the ants would have been living in a dry and barren environment. In Myanmar, on the other hand, they would have lived in a forested, tropical environment.
Not only does the discovery of a Brazilian hell ant improve our understanding of the range of habitats they lived in, it also more fundamentally changes our understanding of ant evolution. While it was thought that ants existed 100-million-years-ago, we now know that they have been on Earth for at least 113 million years.
Not only that, but hell ant headgear suggests specialist foraging behaviour. Given that such specialised ants existed 113 million years ago, this means diversification and specialisation happened in ants much faster than scientists previously thought.
The newly discovered hell ant fossil may be small, but in terms of scientific insight, it is mighty.
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