The Spider with the Catapult Web
An Australian spider has developed a hunting technique that is unique to the animal kingdom. It uses the aggression of its prey to trigger a high-performing snare – shooting ants into its web with enormous force. These are the findings of a joint team of researchers from the University of Greifswald and colleagues from Australia. The results were now published in CurrentBiology.
Predators and prey have been involved in an arms race for millions of years. Some animals strike with lightning speed, others rely on strength or camouflage. A small Australian spider goes the extra step: it has developed a web that functions like a cocked catapult - and which is triggered by the prey itself. The so-called ballista spider (Propostira sp.) lives near to the foraging trails of green tree ants (Oecophylla smaragdina). These ants are considered to be particularly aggressive, territorial and defensive. The spider capitalises on exactly these characteristics.
During the day, the spider hides on the underside of leaves. Shortly after sunset, it begins to build its trap. The trap consists of a fan-shaped system of 15 to 60 silk threads that the spider weaves between twigs and leaves. When it is finished, a small conic silk web stands in place, near to the surface. Shortly after the cone is complete, the first ants appear. They probe it with their antennae and immediately react aggressively. The insects raise their abdomen and bite into the unfamiliar structure – in a similar manner to how they would attack intruders. That is exactly what the spider is waiting for.
The prey itself triggers the catapult
The ant’s bite detaches the silk cone from its anchors. The taut web contracts within approximately only 40 milliseconds. The ant is still holding on to the cone with its mandibles and is thus pulled off the ground.
It is then literally fired at the central web, with ants reaching speeds of up to 4.4 metres per second. The measured maximum accelerations reached more than 1,300 metres per second squared. Individual ants are flung almost 30 centimetres into the central web – an enormous distance for insects of this size.
The spider doesn’t move until the ant is no longer in contact with the ground. It waits until the prey is all tangled up and then wraps it in more silk.
More powerful than anything that can be achieved by muscles
“It is one of the highest performing trapping systems ever found in the animal kingdom,” explains Dr. Jonas O. Wolff, lead author of the study. “In its taut silk threads, the trap stores elastic energy that is released instantly – similarly to a compressed spring. The performance values achieved are several orders of magnitude higher than anything that muscles can provide. Even other spiders with catapult-like webs are outperformed.”
This is made possible by the special architecture of the web. Many taut threads bundle their individual strength and are thus able to overcome the astonishing adhesive characteristics of the ants. The green tree ants have adhesive pads on their feet that can lend them strength far in excess of their own body weight.
Specialised on one species of prey
The ballista spider’s extreme specialisation is particularly remarkable. In all observations, the animals only preyed on green tree ants. Other species of ants, which can be found on the same trees, completely ignored the silken cones. The researchers thus assume that the spider douses the cones with species-specific scents. These could attract the tree ants and also trigger their desire to attack at the same time. The trap would thus not only be mechanically, but also chemically tailored to one individual species of prey.
Evolution at its peak
Green tree ants live in gigantic colonies with millions of workers. They are a reliable source of food for the spider. At the same time, they are dangerous opponents. Catching an individual ant requires separating it quickly from its fellow ants. This is exactly what the ballista spider does with its catapult web. It uses the ant’s defensive reaction as a trigger and flings its prey out of the danger zone within fractions of a second.
“The discovery shows just how far specialisation can go in nature. The permanent competition between predator and prey has led to the evolution of a trap that is amongst the highest performing biomechanical systems currently known,” adds the Greifswald biologist, Dr. Wolff.
Wissenschaftlicher Ansprechpartner:
Dr. Jonas Wolff
Zoological Institute and Museum
Evolutionary Biomechanics
Soldmannstraße 14, 17489 Greifswald
Tel.: +49 3834 420 4243
j.wolff@uni-greifswald.de
Originalpublikation:
Ajay Narendra, Pranav Joshi, Daniele Liprandi, Gregory J. Anderson, and Jonas O. Wolff: Ballistic highpowered spider webs overcome dangerous prey defenses. Current Biology 36, R1–R3, June 22, 2026, https://doi.org/10.1016/j.cub.2026.04.066
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