Ballista Spider: The Catapultous Ant‑Snatcher of Australian Rainforests
A new species of spider has been discovered in the remote rainforests of northern Australia. This minuscule predator weaves a spring‑loaded silk trap that catapults a single type of green tree ant directly into its woven net.
The ballista spider, belonging to the genus Propostira, was seen by researchers from Macquarie University spending daylight hours in gentle webs hidden beneath leaf undersides. At night it drops about 50 cm to the forest floor, anchour its silk line, and builds a tense cone of dozens of tension lines that are “catapult‑like” in design.
When a green tree ant (Oecophylla smaragdina) bites the snare, the trap spring springs, launching the ant as if it had been fired from a Roman ballista. Scientists measured the acceleration to reach roughly 15 times the extreme g‑forces experienced by jet pilots.
Unlike most spiders, the ballista’s net is designed to capture only this particular ant species. Researchers suspect that the spider adds pheromones to its trap to attract and anger green ants, ensuring the prey’s biting behaviour triggers the launch.
The discovery, published in Current Biology, showcases an unprecedented hunting strategy where a web’s mechanism is prey‑triggered rather than predator‑driven, offering new insights into the evolution of spider–prey interactions in the tropics.
Taken together, these observations reveal a sophisticated predatory device designed by evolution to safely handle and consume a typically aggressive ant species that would otherwise threaten other spiders.
