This nocturnal rainforest spider has advanced an unusually specialised searching technique, utilizing a silk-powered snare to focus on a single ant species and launch its prey into the air with remarkable speed and force.
In the rainforest near Cooktown, a green tree ant can trigger its own ambush. The ant bites what looks like a small silk cone near the forest floor, and in that instant the trap fires, flinging the insect upward into a waiting web.
Researchers have documented a newly recognized spider from northern Queensland that appears to hunt with rare precision. The small nocturnal spider uses a spring-powered silk snare to catch one prey species at a time, the aggressive green tree ant Oecophylla smaragdina, in what they describe as “the ultimate specialization.”
Trap targets one ant
The spider has been nicknamed the ballista spider, after the ancient Roman launcher that hurled bolts or stones. It has not yet been formally named, but it belongs to the genus Propostira. Professor Greg Anderson, a biomedical research scientist who is also a spider taxonomist and photographer, first observed it.
A detailed account of the spider’s hunting method and web mechanics appears in Current Biology. To understand how the trap worked, lead researcher Professor Ajay Narendra of Macquarie University and postgraduate student Pranav Joshi spent 10 days and nights in rainforest near Cooktown in far north Queensland. They searched for the spiders, watched their behavior, and filmed the attacks with high speed and infrared cameras.
That fieldwork mattered because ant hunting is dangerous. Ants are not passive prey. They can defend themselves chemically, summon nestmates, and overwhelm predators through numbers.
“It’s very unusual for a spider to feed on ants, because they’re notoriously dangerous, and even more bizarre to find a spider that eats only one particular ant species,” said Professor Narendra. “Ants have a range of chemical defenses—including the ability to sting in some species—and they use alarm signals to rapidly recruit hundreds and even thousands of other ants as backup to overcome potential predators.”
Silk turns into a spring
By day, the ballista spider hides beneath a leaf above places where green tree ants are foraging. After dark, it drops 50cm or more to create an anchor point on a leaf, branch or the forest floor. It then spends as long as four hours building a vertical bundle of 15 to 60 silk tension lines shaped into a cone close to the ground.
The final step turns the structure into a weapon. The spider wraps the cone in a thinner silk and quickly climbs back upward. Soon after, a green tree ant is drawn to the trap, attacks it, and bites the cone loose from its anchor point.
That bite releases the stored tension. The ant is launched more than 30cm upward into the spider’s main web at an acceleration above 1300 meters per second squared. The spider does not rush in immediately. It waits until the ant is trapped in silk, then approaches and wraps it.
“We suspect during the final construction stage the spider adds a pheromone that specifically lures worker ants and induces an aggressive attack, triggering the snare,” said Professor Narendra. “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.”
Silk mechanics reveal extreme force
To examine the silk behind the trap, co-senior author Dr. Jonas Wolff, who studies the biomechanical properties of spider silk, traveled to Australia to see the spider in the wild. He then brought silk samples back to the University of Greifswald in Germany for physical analysis, including scanning electron microscopy, a method that uses electrons rather than ordinary light to reveal fine surface details.
The central question was how such a small spider could lift an ant built to cling. Green tree ants have adhesive pads on their feet, so the trap has to overcome a force far greater than the ant’s body weight. The answer appears to be stored elastic energy, the same basic principle behind a stretched rubber band, but built from silk.
“The ballista spider’s snare is bioengineered to store elastic energy in the silk and rapidly release it, giving it incredible instantaneous power density—greater than any other specialized silk-based biological catapults,” said Professor Narendra. “The ants it preys on have adhesive pads on their feet, so the contraction of the bundle of tension lines has to overcome a force of many times the ant’s body weight to lift it.”
“The snare mechanism seems to have evolved as a highly specialized 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.”
Reference: “Ballistic high-powered spider webs overcome dangerous prey defenses” by Ajay Narendra, Pranav Joshi, Daniele Liprandi, Gregory J. Anderson, and Jonas O. Wolff, 22 June 2026, Current Biology.
DOI: 10.1016/j.cub.2026.04.066
This research was funded by an ERC Starting Grant (101040724 — SuPerSilk) under the European Union’s Horizon 2020 research and innovation program to J.O.W. and an Australian Research Council Discovery Project grant DP220102836 to A.N.
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