In Northern Australia, researchers recently observed a newly discovered spider species securing its prey by engineering a cone-shaped silk trap that violently catapults ants upward the moment they bite its tethered base, the BBC reports.
The unique hunting method was developed by the nocturnal predator to hunt for aggressive ants, which are dangerous and an unusual prey for arachnids. The cone-shaped trap can fling an ant at an extremely high force, the magnitude of which is 15 times higher than that experienced by jet pilots, BBC cited Professor and researcher Ajay Narendra as saying.
The species is yet to receive its scientific name; as of now, it is named “Ballista,” a weapon used to throw stones in a battle during ancient times.
Arachnid engineering marvel details
“The snare mechanism seems to have evolved as a highly specialised way of allowing the spider to ‘pick off’ potentially hazardous prey one at a time and transport them a safe distance away from ant trails and nests,” BBC quoted researcher Dr Jonas Wolff as saying.
Ants have developed formidable defenses to fend off predators. Beyond delivering a vicious sting, a single ant can trigger a massive invasion, mobilising an entire army of workers to its aid, Narendra explained.
How was the experiment carried out?
A team from Australia’s Macquarie University spent 10 nights in a tropical rainforest of northern Queensland observing the spider’s behaviour through high-speed and infrared camera equipment.
Current Biology published its findings, explaining the habitat of the balista spider. Hidden in webs beneath the leaves, the species reside among the aggressive and territorial green tree ant Oecophylla smaragdina.
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At night, it drops to 50 cm to a leaf, branch, or forest. This becomes the anchor point to start building the trap. The green tree ant is the only species that is attracted to the trap.
The spider invests hours in constructing a cone-shaped scaffold composed of numerous tension lines, then sheathes it in finer silk before retreating. Observations revealed that when green ants bite the structure, the snare instantly triggers, catapulting the prey into the spider’s web with extreme acceleration, BBC reports.
High-tech spider captured in motion building a cone shaped trap for the prey. (Pranav Joshi, Macquarie University)
The spider’s trap deploys so rapidly that researchers initially missed it on high-speed cameras. Later filmed at 5,000 frames per second, the snare accelerates at an astonishing 4,921 kilometers per second—100 times faster than a Formula One car. This highly energetic, finely tuned mechanism even outperforms famous slingshot spiders, CNN reports.
According to CNN reports, the trap turns the ant’s natural aggressiveness into a weakness. Flinging the ant into the air pulls it safely away from the rest of its group. Researchers hypothesise that this rapid extraction prevents the spider from being overwhelmed by a swarm of retaliating workers. However, it remains a mystery why green tree ants are the only species observed aggressively attacking the snare. They suspect the spider coats the silk with a special scent that only triggers green tree ants to attack.
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“This is a remarkable discovery because it combines two aspects that are rarely seen together: extreme biomechanical performance and a high degree of ecological specialization,” Leonardo Delgado-Santa, a professor of biology at the University of Quindío in Colombia and a researcher with the Ecdysis Research Group, not involved in the research, explained in an email to CNN.
The spider exclusively catches green ants, completely ignoring other nocturnal species nearby. Scientists suspect the trap is laced with specific pheromones designed to lure and provoke only the green ants.
“This seems to be the only case where a spider’s web is designed to catch a single prey species, and where the mechanism is triggered by the prey rather than by the predator,” BBC quoted Narendra as saying.
Researchers are eager to understand the ballista’s family tree and to uncover the mysterious ability of the species.
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“Other species of Propostira are found in Asia, and we are keen to determine their hunting strategies,” said Narendra.
(The article is curated by Salonee Kulkarni, who is an intern with The Indian Express)
