Webs Communicate Only What Matters

Spider on web, showing how attuned the spider is to vibration in the web.

Biological Strategy

Spiders

Sam Stier

Image: Rachel Hahs / Flickr / Public Domain - No restrictions

Differentiate Signal From Noise

The environment surrounding any living system is full of signals, such as smells, sounds, electricity, magnetism, and more. Too many signals at once can be overwhelming, making it difficult to locate and react to any particular signal. To address this, living systems must differentiate among all signals, or “noise,” so they can focus on those they really need. During mating season, for example, male frogs gather close together in large groups to call for females. Despite their overwhelming, collective noise, females are able to find a particular male whose call is attractive to her. This is because the males use desynchronized calling, enabling individual recognition.

Search this Function

Arachnids

Class Arachnida (“spider”): Spiders, mites, ticks, scorpions

Arachnids get a bad reputation, but they play an important role in the ecosystem by controlling insect populations. Almost half of the species in the class are spiders, and most live in terrestrial environments. Unlike insects, most arachnids have two body sections: the cephalothorax, which is the head and thorax fused together, and the abdomen. Mites and ticks, on the other hand, have only one body section that is relatively flat. This body shape comes in handy for the species that are parasitic, because it makes it harder for their hosts to bite or scratch them off.

Search this Living System

Spider webs dampen ambient vibration while efficiently transmitting point source vibrations from caught prey.

Introduction

A morning breeze sweeps over the high mountain valley, pushing grasses into convulsive, hypnotic waves. And yet, it’s not the wind that makes the spider web strung within the saskatoon bush shudder.

While the web hardly moves from the breeze and bending plants, the vibrations conducted through the web from a hapless fly reach the orb weaving spider in milliseconds, her eight legs triangulating the trapped fly’s exact position. In a flash, she is right by its side, dispatching her prey with venomous fangs.

The Strategy

A spider web’s design and properties can both easily transmit “point source” vibrations from the impact of an insect landing on the web, and dampen ambient vibrations that come from a billowing wind.

In addition, the silk dampens vibrations that come to the web from whatever the web is attached to. This is because when physical vibrations encounter a change in material, some energy gets transmitted while some is reflected backward. The more dissimilar the substances (for example a dense wooden tree branch and wispy spider silk), the more energy gets reflected away.

In these ways the webs’ general dampening tendency and the physics of vibration transmission insulate webs from disturbance by external sources, keeping the channel clear for spiders to detect what matters most to them.

The Potential

Interactive technologies only work as well as the sensors that inform them. A semi-automated car, for example, can only protect you from collisions if it can accurately detect other cars. Sensors run into trouble, however, the more sensitive they become, due to ambient “noise”. Suddenly, your car slams on the brakes not because of another vehicle, but because its sensor gets tripped by the car engine’s heat or vibrations from the road.

A spider web’s unique ability to efficiently transmit information produced internally while remaining insulated from outside ambient noise has proven a useful model for overcoming these challenges. New microchip sensors inspired by spider webs, for example, have recently been designed with applications to quantum computers, astronomical research, and more.

Last Updated September 21, 2023

References

“We have performed dynamic experiments on full spider webs in order to characterize their shock response. Our experiments confirmed that a spider web can be described as a dynamic system, which has time-dependent properties as the impact-caused vibrations decay. Considering the orbweb as a single-degree-of-freedom system, allowed for the description of the amplitude, the period duration, and the energy dissipation during impact. The stiffness plots obtained as function of displacement confirmed that stiffness is not constant and its value increases steadily during the first few vibration cycles after impact, allowing for increased energy dissipation. This energy dissipation exceeds the values predicted by a linear model, confirming that the webs of orb-web spiders are optimized to dissipate the kinetic energy of large flying prey…” (Tietsch et al. 2016: 4-5).

Journal article