A new study in PLoS One has revealed that the mysterious silk decorations in some spider webs may be sophisticated tuning devices that enhance the spider’s ability to locate its next meal by controlling how vibrations travel through the web. For centuries, the thick, zigzag patterns of silk, known as stabilimenta, found in the webs of common garden spiders and other species have been a matter of debate. Some scientists proposed they act as a visual lure, reflecting UV light to attract unsuspecting insects.

Others suggested they serve to warn larger animals like birds from accidentally destroying the web or perhaps as camouflage to conceal the spider lying in wait. The evidence for these ideas has often been contradictory, and the fact that spiders don’t always build stabilimenta has only deepened the mystery. The authors of the new study, from Denmark, Italy, Sweden, and the UK, identified a crucial gap: spiders are masters at sensing vibrations, yet scientists hadn’t explored how the stabilimenta might affect how vibrations travel through the web.

The researchers first observed and categorised the diverse range of stabilimenta shapes built by the wasp spider (Argiope bruennichi). Then they used this real-world data to create sophisticated computational models of spider webs, simulating prey getting trapped at various points and analysing how the resulting vibrations travelled to the centre. The simulation revealed that for vibrations traveling directly towards the spider along the web’s ‘spokes’ or moving perpendicular to the web plane, the stabilimenta had a negligible effect on signal travel time.

But for vibrations that moved sideways along the web’s threads, they made a big difference. In webs with a stabilimentum, these vibrations were able to reach many more output points at the web’s centre.

This suggested the ‘decoration’ enhanced the spider’s ability to quickly locate its prey. Per the study, the finding has many implications for biology and for engineering.

Among biologicalists, the newly understood role of stabilimenta could help explain the complex balance spiders need to strike between the need to detect prey and the risk of being detected by predators. Engineers could add simple geometric features to control the flow of wave energy in materials of the future. Imagine structures that can dampen unwanted noise, highly sensitive acoustic sensors that can pinpoint a sound’s origin, and advanced protective gear that efficiently guide the force of an impact away from the body.