A new study has identified an unusual hunting mechanism in the rainforests of northern Queensland, Australia, where a spider from the genus Propostira uses a silk trap that works like a tiny ballista. The trap is not triggered by the spider, but by the prey itself, and researchers say it is among the most effective capture systems ever documented in nature.
The spider, nicknamed the “ballista spider,” constructs its trap at night, about half an hour after sunset, on the underside of leaves near ant trails. Over several hours it spins 15 to 60 taut silk threads into a cone close to the ground, then wraps the structure in a thinner layer and tensions it like a loaded spring. When an ant touches the cone and bites it in an attempt to dismantle it, the stored tension is released in about 40 milliseconds.
The result is dramatic. The ant is flung upward as high as 30 centimeters at a speed of about 4.4 meters per second, with acceleration exceeding 1,300 meters per second squared. In 35 recorded observations, every successful capture was of the green tree ant, Oecophylla smaragdina, while other ant species sharing the habitat did not react to the silk structure.
Researchers believe the spider may release a specific pheromone while building the trap, attracting only these aggressive ants and provoking their attack response. Dr. Ajay Narendra of Macquarie University said, “This is likely the only example where spider silk is designed to catch a single species, and the mechanism is triggered by the prey, not the predator.” Lead author Dr. Jonas Wolff, of the University of Greifswald, said the system is “one of the highest-performance capture systems found in the animal kingdom,” with measurements far beyond what muscles can produce and even above those of other catapult-like spiders. The team thinks the strategy helps the spider handle dangerous, group-moving ants by isolating one individual and removing it from the trail.
