Researchers from Greifswald and Australia describe catapulting spider as an extreme prey specialist

The spider, referred to by the researchers as the ballista spider (Propostira sp.), begins building its trap about 30 minutes after sunset. From a main web, it stretches several long threads, which it anchors close together to branches or leaves. If a prey animal touches the construction, the threads are suddenly tensioned and hurl the victim toward the web.

In all 35 documented observations, the spider caught exclusively ants of the species Oecophylla smaragdina, known as weaver ants. The authors interpret this pronounced specialization as an indication of close coevolution between predator and prey, in the course of which the capture mechanics have become increasingly refined.

Prey specialization on weaver ants

The team attributes the extreme acceleration to a combination of pre-tensioned silk threads and a trigger mechanism that operates without muscular force. The "This power-amplified capture device impressively demonstrates how extreme ecological specialization can drive the evolution of extraordinary biomechanical performance."

Jonas Wolff from the University of Greifswald, one of the senior authors, places the findings in the context of other specialized spiders. "It is one of the most powerful known capture systems in the animal kingdom," says Wolff. "Even other spiders with catapult-like capture webs are surpassed."

Mechanics beyond muscular force

Wolff adds: "From the constant contest between predator and prey, a trap has emerged that belongs to the most powerful biomechanical systems known to date." The researchers emphasize that the construction far exceeds the efficiency of muscle-driven jumps.

"The discovery shows just how far specialization can go in nature," the authors summarize. They regard the finding as evidence that passive, pre-tensioned mechanisms can produce more powerful solutions in evolution than active muscular work.

Open questions and outlook

It remains unclear for now how the spider coordinates the trigger within milliseconds and which sensory stimuli of the ants activate the mechanism. The researchers announce further field observations in Australia to investigate the construction more closely under natural conditions.

The study was conducted in cooperation with Australian partner institutions; the results were published in the journal "Current Biology." The authors describe the system as "the ultimate specialization" and see it as a model system for biomechanical research, for example for the development of energy-efficient microsystems.