Spider Webs Are Big Ears

A spider web is not just a trap for prey.
It’s also a giant acoustic sensory antenna.

 

Spider Uses its Web Like a Giant Engineered Ear (The Scientist). Report Dan Robitzki likens this finding to how SETI researchers build big antennas to capture faint signals from stars. His subject, though is a spider called a bridge spider or gray cross spider. “Bridge spiders ‘outsource’ their hearing by building webs that double as acoustic arrays,” he says, “allowing them to perceive sounds from great distances.” The investigation into this feat was published as a preprint by Jian Zhou and six others in bioRxiv on Oct 18, 2021, “Outsourced hearing in spiders by using their webs as auditory sensors.” Even though this “engineered” capability has only been observed in one type of spider so far, the idea is a game changer, Robitzki says.

However, Hoy and Miles suggest that external-ear behavior may not be restricted at all—they speculate that they’ve scratched the surface of a whole world of spider and insect sensation that could change our understanding of bioacoustics at a philosophical level.

“Most [biologists] assume that insects can sense sound only when it’s really near,” Hoy says. The study demonstrates, he says, “that it’s time to look again at animals that are hairy. A simple hair is a perfectly legitimate sound system because it’s sensing flow.”

The hairs on a spider’s legs are sense organs that can receive vibrations that have been “outsourced” to the web it constructed. This is similar to what humans do by engineering sensory devices, such as radio dishes and TV antennas, to detect signals larger than themselves.

Experiments showed that the bridge spiders were picking up the sensations through their leg hairs touching the web, and not through their ears. The spiders elicited an alarm response to “carefully-engineered and directed sound stimulus that hit the web but not the spider sitting in the center.”

Robitzki calls this a “giant-ear trick.” It enlarges the sensory capabilities of spiders by a wide margin. The preprint says,

The behavioral response of spiders to minute web vibrations induced by the focal airborne sound confirms their abilities to perceive airborne acoustic signals solely by detecting web movements. Given a web-enabled hearing threshold lower than 68 dB (Fig. 3d), orb-weaving spiders should be able to detect and localize predators and prey such as birds and crickets at a distance more than 10 m away, considering the sound loudness produced by distant animals (Supplementary Table 2).

Further studies might find this capability present in many more arachnid species, and perhaps in other animals, too.

The discovery that the bridge spider uses its web as an external auditory sensor is fascinating, University of California, Davis, arachnologist Lisa Chamberland, who didn’t work on the study, tells The Scientist, because it’s such a drastic departure from what scientists previously assumed about a spider’s hearing. 

“I think this opens up doors for some exciting research,” Chamberland says, adding that she hopes scientists will start “looking at the evolution of sound systems across spiders.”

False Attribution

There’s the obligatory e-word, evolution. Why does it pop up here? Do the scientists really believe that an “engineered” system like the web antenna just happened by blind natural forces? One needs to ask what purpose the e-word serves in this article:

• “’Evolutionarily speaking, spiders are just weird animals,’ Jessica Petko, a Pennsylvania State University York biologist who didn’t work on the new study, writes in an email to The Scientist.”
  • Why evolutionarily speaking? Why not just speaking?
• [Chamberlain] “hopes scientists will start “looking at the evolution of sound systems across spiders.”
  • Why the evolution of sound systems? Why not the biological function of sound systems?
• “Another question, he [University of Cincinnati biological sciences professor George Uetz] adds, is how differences in webs among species ‘could impact both the process of sensing and function in prey capture and communication, which is an important evolutionary question.’”
  • Why an evolutionary question? Why not just a question?
• “’It will be interesting to find out whether other web building spiders (like the ones that make messy cobwebs) use webs for a similar purpose or if this evolutionary marvel is restricted to orb weavers,” Petko writes.”
  • Why an evolutionary marvel? Why not just a marvel?

Such insertions of “evolution” appear to be reflexes or habits, not carefully pondered ideas.

Darwinism Without Ear Review

The preprint article has similar pinches of incense tossed to the Bearded Buddha, for no apparent reason. “The auditory organs of these animals are extremely diverse in anatomy after hundreds of millions of years of evolution,” the authors begin, without explaining how tiny animals with small brains conceived of and manufactured their sophisticated ears. They just assume they did. Similar to the PopEye Theory of Evolution (17 August 2019), the Imagine-Ear Theory of Evolution puts the origin of ears into Darwin Fantasyland. When you wish upon a star, ears just app-Ear as if they were Engin-Eared by the engine of natural selection. Why? Sounds exist. Animals could benefit from hearing them. So Chuck-in-the-Box, the Tinkerer, popped up and supplied them.

During the water-to-land transition, animals have gone through dramatic challenges in aerial hearing. To effectively detect weak, distant airborne sound, terrestrial vertebrates and some invertebrates have evolved the tympanic eardrums which are very sensitive to the pressure component of sound. Alternatively, some arthropods, especially those of miniscule size, have evolved pendulum-like, long wispy filaments to detect the velocity component of sound. While the auditory organs of different animals are extremely diverse in anatomy after hundreds of millions of years of evolution, they are all organs of cellular origin and hence embodied. Hence, they are necessarily constrained by morphogenesis….

Here we show that the highly responsive aerodynamic property of silk fibers are woven and stretched into diaphanous orb-web can function as a huge acoustic array “antenna,” which allows the spider to efficiently detect faint airborne sound from a distant source. This outsourced web-array “ear” operates on a very different principle from the much smaller embodied auditory organs of all other animals.

The actual methods and results in the paper, however, never mention evolution again. In fact, the authors point to spider silk and now this acoustic marvel (the “giant-ear trick”) as inspirations for human engineering.* The applicable conclusions, therefore, relate to intelligent design – not to Darwinism.

Miracles seem less magical if they can be stretched out over hundreds of millions of Darwin Years. The moyboys wave their magic wands of natural selection, and speculate that organs of hearing app-Eared, along with the brain software to use them. Evolutionists often forget that software requirement. The animal must be able to perceive the electrical input transmitted by the organs through nerves and respond to it with programmed actions. Without the software, the vibrations would fall on deaf ears.

Let’s Sing!

Old McDarwin had a yarn, EIEIO. And in this yarn out popped an eye, EIEIO.
With a blink-blink here and a blink-blink there, here a blink, there a blink, everywhere a blink-blink
Old McDarwin got an eye, EIEIO.

Old McDarwin had a yarn, EIEIO. And in this yarn he imagin-eared, EIEIO.
With a buzz-buzz here and a buzz-buzz there, here a buzz, there a buzz, everywhere a buzz-buzz
Old McDarwin got an ear, EIEIO.

Old McDarwin had a yarn, EIEIO. And in this yarn out popped a wing, EIEIO.
With a flap-flap here and a flap-flap there, here a flap, there a flap, everywhere a flap-flap
Old McDarwin got a wing, EIEIO.

(Note: EIEIO stands for “Evolution is Empty Imagination-based Obscurantism.”)

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* quote from the preprint about engineering applications of spider designs:

Biologists and material scientists are still discovering new properties of spider silk that can be repurposed as a biomaterial and deployed for practical human applications. Here, we demonstrate how a spider web made of nanoscale protein fibers serves as a megascale acoustic airflow sensor, contrasted sharply with all auditory organs made up cellular tissue, and necessarily subjected to morphogenetic constraints. By getting rid of the morphogenetic constraint, the sensory surface area is up-scaled extensively, much as a radio-telescope senses electromagnetic signals from cosmic sources. The web is analogous to an eardrum in other animals, but it senses the velocity of air particles, not its collective pressure. Spider webs are marvels of bio-architecture that greatly extend the spider’s capacity to sense and capture prey much larger than the spider itself. The spiders also have the flexibility to tune and regenerate their hearing by manipulating the orb-webs. The novel hearing mechanism could provide unique features for studying extended and regenerative sensing, and presage a new generation of acoustic fluid-flow detectors in the domain of nanoscale biosensors for applications requiring precise fluid dynamic measurement and manipulation.