Load, hold, release
A fly hits the web. Instead of simply waiting for it to become tangled, Hyptiotes cavatus releases a trap it has already loaded. Both the spider and its triangular web spring forward.
The spider prepares by pulling the web taut over repeated movements. Each movement adds stored elastic energy to the silk. When prey strikes, releasing that tension delivers the energy in a sudden burst: the web acts like a catapult.
The launch is only part of the trap. An abrupt stop makes the web oscillate, bringing extra capture threads against the insect and wrapping more silk around it. A seemingly delicate triangle becomes a moving net.
About 79 g—and a clear difference in capture
The 2019 study recorded a peak spider acceleration of 772.85 m/s², approximately 79 g. That is a measured maximum during laboratory releases, not the acceleration of every strike.
The prey observations showed why releasing the web matters:
- No release: all 11 flies escaped.
- Web released: 21 of 29 flies were captured, about 72%.
- Extra silk: additional capture threads contacted prey in as little as 4 milliseconds.
These are results from the study's fly trials, rather than a universal capture rate for every prey species or field situation.
A 2025 clue in the silk genes
A follow-up published on 4 November 2025 in PNAS Nexus examined the material behind the mechanism. Researchers found an expanded set of silk genes encoding exceptionally proline-rich proteins, and confirmed unusually high proline content in the silk itself.
Proline is an amino acid associated with several mechanical properties of spider silk. This unusual composition may suit the demands of storing and rapidly releasing energy.
The functional link remains unresolved. Standard tests did not show greater extensibility than in related spiders, and the study did not establish that the extra proline causes the catapult's performance. Further testing is needed to identify which properties matter during a strike.
A web as part of the hunting system
The catapult mechanics were published in 2019; the genetic follow-up adds a later chapter. Together, they make this an unusually clear example of how an animal's behaviour and the material it produces can become one hunting system.
The result shifts attention to the whole system the spider builds: silk, geometry and timed movement all contribute to the strike.
Read the papers and watch the mechanism
- 2019 catapult study: External power amplification drives prey capture in a spider web, published 13 May 2019 in PNAS. Its supplementary-material links include the researchers' high-speed videos.
- 2025 silk-gene study: Triangle weaver spiders construct spring-loaded webs using a novel set of genes for exceptionally proline-rich silk, published 4 November 2025 in PNAS Nexus.