In Australia, scientists have discovered a spider whose loop-shaped trap is designed specifically for one type of ant. When the victim triggers it, the force of acceleration is so immense that it could kill a human, instantly flinging the prey into the web. The findings of this study were published in the journal Current Biology.
The acceleration recorded by the researchers reached 1,367 meters per second squared—this occurs when green tree ants (Oecophylla smaragdina) disturb the loop trap. This force is 130 times greater than Earth’s gravitational pull.
“To capture this on film, we had to boost the frame rate to 5,000–7,000 frames per second. Honestly, I’ve never had to film animals like this before,” shares Ajay Narendra from Macquarie University in Sydney.
In 2022, Greg Anderson from the QIMR Berghofer Medical Research Institute in Brisbane, Australia, witnessed a green tree ant getting caught in a spider’s trap in northern Queensland. However, due to a lack of suitable camera equipment, he could only make out a blurry smudge—the prey had been launched by a ballistic motion from a strange cone-shaped web.
In early 2023, Narendra and Pranav Joshi, also from Macquarie University, spent ten days studying and filming these nocturnal spiders. They don’t yet have a scientific name, but they belong to the genus Propostira.
These spiders have been nicknamed ballistae—after the ancient Roman siege weapon, similar to a crossbow, that hurled heavy stones hundreds of meters.
During the day, the spiders hide under leaves, and as dusk falls, they begin weaving their trap—a process that takes up to four hours. In that time, they create between 15 and 60 tightly stretched threads, which are attached to a leaf and form a cone.
Once the trap is ready, they apply a chemical substance to it. This substance causes green tree ants (but not other insects) to attack the web with their jaws.
“I think the web contains a lot of sticky material,” explains Narendra. “The jaws get stuck, and the ant can’t unclench them to free itself.”
When the ant tries to escape the trap, it releases the point where the web is anchored. At that moment, the taut threads tied to the cone fling it nearly 30 centimeters into the air, and it lands directly in the spider’s main web.
It’s likely that the spiders use this method to lift the prey away from ant trails, avoiding a dangerous attack from the entire colony, Narendra believes.
Building a trap each time for food might seem overly labor-intensive, but green tree ants are an unusually stable food source, he adds. “When the spider needs to eat, it just comes out, weaves a new web—and dinner is ready.”
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