​On the chain gang: Meet Siem Reap's very own ant man | Phnom Penh Post

On the chain gang: Meet Siem Reap's very own ant man

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Publication date
14 August 2015 | 22:23 ICT

Reporter : Nicky Sullivan

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Cambodian Leptogenys ants attack their prey as a team. STEPHANE DE GREEF

Stephane De Greef’s enthusiasm for all things creepy and crawly is infectious. Hitting the trails with the Siem Reap-based bioengineer and photographer, it’s impossible not to feel the same delighted wonder he experiences every time he steps foot into a forest.   Finding an army of termites on the forest floor invading an ant nest, leading to an epic showdown that makes the battles in Game of Thrones look pedestrian, he delivers a fascinating running commentary. There’s flanking and sieging, alternative routes of attack and defence and lots of talk of mandibles. It’s genuinely riveting stuff as his passion for these tiny six-legged creatures opens up whole new and complex worlds. It’s this passion that also led De Greef and Dr Christian Peeters, an evolutionary biologist from the Pierre and Marie Curie University in Paris, to the discovery of an extraordinary and entirely undocumented behaviour among a genus of Leptogenys ants native to Southeast Asia. “We were on Phnom Khulen in 2012 looking for some rare ants, and turned around and saw this huge line of ants dragging a millipede,” he said. “Christian is one of the world’s specialists in this genus, and he’d never seen or read anything about this before.” In the language of a true geek, De Greef added: “We knew this was really special and that we had to do something about it.”

Predation on large millipedes and self-assembling chains in Leptogenys ants from Cambodia from Stephane De Greef on Vimeo.

But life, work and a lack of funding got in the way until last year, when a poorly shot video, most likely from Thailand, of ants engaging in the same behaviour hit the web stirring up a lot of interest from around the world. Suddenly the pressure was on the pair to get out and document what they had seen. They just had to find the ants again. “We know they kill the millipedes, who like nice moist forest, so that was where I started,” said De Greef. “The problem with these ones though is that they don’t stay in one place. So every time I found them, I’d have to find them again every time I went back.” Moreover, the ants are highly aggressive and not afraid to use a powerful stinger, just like a wasp’s, on their tail. After four days though, the Belgian finally found them in Angkor Thom, and it wasn’t long before he was able to observe the unique behaviour that allows these tiny blue insects to attack prey significantly larger than them. The ants carefully hold back until their prey is lulled into a false sense of security, leading it to unfurl from its heavily armoured defensive coil. The exposure is exploited by a single ant that dives in to deliver a shocking sting in the sensitive area between the millipede’s legs, causing it to spring back sharply and triggering a swarming attack by up to 50 more ants. It makes for pretty brutal viewing. Once the prey is subdued, the ants assemble into long chains using their mandibles – external mouthparts – to latch on to antennae or other parts of their nearest cohorts, and then drag dinner home. “These things weigh over 1,000 times more than an individual ant. It’s like you or me trying to attack a train,” said De Greef. De Greef and Peeters’ scientific paper on the behaviour was published last Saturday, once again prompting a swirl of interest across the world. For De Greef, this can only be a good thing. “We know nothing about Cambodia’s insect diversity, less than 1 per cent. And there are tens of thousands of species out there,” he said. Unfortunately, he said, just as mammals are going extinct, thousands of invertebrate species are also disappearing. Some may shrug at the prospect of losing creatures that seem to do little more than invade sugar bowls and crowd kitchen worktops, but ants, and insects in general, are essential parts of their ecosystem, and may also carry valuable information with important applications in health or agriculture. “Ants eat and are eaten, so without them, we may find our crops overtaken by caterpillars, or species of bird that no longer have a food source,” said De Greef. More broadly, the study of ants has led to increased understandings in the fields of traffic control, logistics, computer programming and disaster preparedness. According to De Greef, the unique behaviour of these blue unnamed ants also has much to teach us. It has mechanical implications, allowing them to hunt something that is much larger than themselves, and we need to understand more about how they do it,” he said. In Cambodia, De Greef strongly feels that we need to increase awareness and understanding of insects if we are to have any chance of preserving them and their valuable services and knowledge that can be gained from them. He hopes that his and Peeters’ discovery will help lead to an increased focus on this area.

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