A symbiotic Ecitophya simulans rove beetle (foreground) walking alongside its lookalike army host ant, Eciton burchellii (left). The ant has a large round head, whereas the beetle has a flatter head. The beetle is the imposter. Image: Taku Shimada
Beetles have worked out a way to secretly invade ant colonies and eat their brood. Even stranger, they’ve evolved to do this over and over again.
Nature has produced some incredibly innovative evolutionary quirks that have allowed certain species to survive, thrive and team up to mimic, invade and destroy.
Ladies and gentlemen, The Beetles
Pandas have survived without showing any real abundance of willingness to do so; humans have thrived to such a degree that we’re doing our best to ruin the planet; lizards let striped bark scorpions live in their cool, ideal lair in return for the latter’s protection from other dangers; and, for mimicry, invasion and destruction, nature provides us with the rove beetle and the army ant.
A new study has shown how the rove beetle has outwitted the army ant by disguising itself as one of their own, copying their behaviour and then, when the time is right, dining on the ants’ brood.
Weirder still, the evolutionary path that the rove beetle has gone down – dramatic changes in body shape, behaviour and pheromone chemistry – has happened on at least a dozen separate occasions in history.
This means that evolution may not be as unpredictable as some believed.
This image shows nine convergent rove beetle genera that have evolved to look like different army ant species. Top row, left to right: Weissfloggia, Ecitocryptus, Ecitoglossa. Middle row: Aenictoteras, Giraffaenictus, Pseudomimeciton. Bottom row: Dorylogaster, Diploeciton, Aenictolixa. Image: Munetoshi Maruyama and Joseph Parker
You say you want an evolution
“These beetles represent a new and really stunning system of convergent evolution,” says Joseph Parker, study co-author and evolutionary biologist at Columbia University.
“It’s an elaborate symbiosis, which has evolved in a stereotyped way, multiple times from free-living ancestors.”
The evidence of this behaviour, in so many isolated incidents, stretches back to the Early Cretaceous period. What’s important about this is the previously held belief by some biologists that evolution follows a somewhat random path.
Parker and his co-author Munetoshi Maruyama of the Kyushu University Museum argue that their finding challenges Stephen Jay Gould’s hypothesis that if time could be rewound and evolution allowed to replay again, very different forms of life would emerge.
“The tape of life has been extremely predictable whenever rove beetles and army ants have come together,” says Parker. “It begs the question: why has evolution followed this path so many times?”
Two Pseudomimeciton rove beetles walking alongside the Labidus ant they’ve evolved to resemble. The ant is darker, whereas the beetle is more red. Image: Taku Shimada
Twist ant shout
Rove beetles are armed with glands that secrete defensive chemicals, so a beetle encountering an ant troop stands a much better chance of surviving than most insects do. To change shape and grow an ant-like appearance, it relies on a flexible body.
It’s impossible that the beetles’ most recent common ancestor (105m years ago) was an army ant doppelgänger, though the researchers think it probably possessed traits that would allow its descendants to readily evolve into army ant parasites.
“There’s been this explosion of ants over the past 50-60m years that must have radically changed terrestrial ecosystems,” said Parker. “Army ants were part of that. They presented this huge niche for exploitation that these beetles were equipped to exploit, and they did so multiple times in parallel.
“If we want to understand life on Earth, we have to study groups like rove beetles. These tiny insects comprise the largest family of animals. We need to know how they live, how they evolved and what role they play in the environment. Amazing things come from doing that.”
