Scientists Discover Deadly 'Ballista Spider' That Fires Ants Sky-High With Silk Spring Trap

A newly discovered species of spider in Australia has amazed scientists with one of the most unusual hunting strategies ever documented. Nicknamed the 'ballista spider,' the tiny arachnid constructs an elaborate spring-loaded web capable of launching ants through the air at speeds approaching 10mph.

The remarkable discovery was detailed in a study published on 22 June in Current Biology. Although the spider belongs to the genus Propostira, researchers say it has yet to receive an official species name.

The spider was first spotted in 2022 by metabolism researcher Greg Anderson while exploring a remote rainforest in northern Queensland. Anderson witnessed a green tree ant suddenly being flung into the air before becoming trapped in a spider's web – an event so unusual that he contacted fellow scientists to investigate.

In early 2023, biologists Ajay Narendra and Pranav Joshi from Macquarie University travelled to the rainforests of Queensland's Cape York Peninsula equipped with high-speed cameras. Over 10 days of observation, they documented the spider's extraordinary hunting technique in detail.

How Does the Ballista Spider Trap Its Prey?

During the day, the nocturnal spiders remain hidden beneath leaves. As evening approaches, they spend up to four hours constructing an intricate hunting device. Starting from their main web, the spiders descend about 18 inches before attaching between 15 and 60 silk tension lines to a lower anchor point, such as a leaf, branch or the forest floor. They then twist the silk into a tightly wound cone-shaped structure wrapped in finer strands.

Researchers suspect the spiders coat the cone with pheromones that attract green tree ants while leaving other ant species uninterested, although this has not yet been confirmed. When a green tree ant investigates, it instinctively bites the cone. Scientists also suspect the sticky silk prevents the ant from releasing its grip.

As the trapped ant struggles, the tensioned cone suddenly detaches from its anchor point in roughly 42 milliseconds. The stored energy is instantly released, catapulting the insect nearly a foot into the air before it lands in the spider's main web, where the waiting predator captures it.

According to the study, the launched ants can reach speeds of up to 14.4 feet per second and experience accelerations equal to approximately 140 times the force of gravity – around 15 times greater than the maximum g-forces typically endured by fighter jet pilots.

Why Is the Discovery So Important?

Researchers also found that the web stores and releases energy more efficiently than any previously documented silk-powered biological catapult, surpassing even the well-known slingshot spider.

The team believes this highly specialised hunting strategy evolved because green tree ants are abundant throughout the rainforest and remain active year-round. However, the ants are also aggressive and highly territorial. By isolating and launching individual ants into its web, the ballista spider may be able to capture prey without alerting the rest of the colony.

Scientists say the discovery represents one of nature's most sophisticated examples of biomechanical engineering and ecological specialisation. Unlike other known spider webs, the ballista spider's spring-loaded trap appears uniquely adapted to target a single prey species, making it a rare example of extreme hunting specialisation in the animal kingdom.

The researchers hope the findings will lead to a better understanding of how spiders evolve highly specialised hunting techniques and how nature develops remarkably efficient biological engineering systems.