🕷️ A spider invents an ant catapult

In the tropical forest of northern Queensland, Australia, a small nocturnal spider has developed a hunting technique as ingenious as it is surprising. Nicknamed the ballista spider after a Roman war weapon, it uses a mechanical web to catch, one by one, a single species of ant. Such a level of specialization has never been observed in arachnids before.

This spider, which belongs to the genus Prostopira, was first observed by Professor Greg Anderson. Later, Professor Ajay Narendra's team from Macquarie University spent ten days and nights studying its behavior using high-speed and infrared cameras. Their work is published in the journal Current Biology.


The construction of this trap begins at dusk. The spider descends from a leaf where it hides during the day, then spends up to four hours weaving a set of 15 to 60 stretched silk threads, gathered into a cone near the ground. It then envelops this cone with a finer thread and quickly climbs back up to its main web.

A few seconds later, a green ant, attracted by a pheromone that the spider may have added during construction, bites the cone out of aggression. This action releases the tension stored in the silk threads, launching the ant more than 12 inches (30 cm) into the air with dizzying acceleration. The spider then only has to wait for the prey to be immobilized in its web before wrapping it in silk.

This hunting mechanism is unique. Unlike other spiders, the prey itself triggers the trap. Moreover, the ballista spider only targets a single ant species, the green ant Oecophylla smaragdina, known for its collective defense and painful stings. The trap allows the spider to capture these dangerous insects one by one, far from their nestmates.

Silk samples were analyzed under an electron microscope by Dr. Jonas Wolff of the University of Greifswald. The silk stores phenomenal elastic energy, more powerful than any other known biological catapult. This power is necessary to lift an ant whose legs strongly adhere to surfaces.

Evolution has thus equipped this spider with a formidable weapon for a very specific menu.