by Ovid metamorphosis speaks of the sphere weavers, called descendants of Arachne, a figure from Greek mythology who wove beautiful tapestries and dared to challenge Athena to a weaving contest. Angry at not finding fault with Arachne’s work – and also because the tapestry depicted the gods in an unflattering light – Athena beat the girl with a shuttle. When Arachne hanged herself out of remorse, Athena took pity and turned the rope into a web and Arachne into a spider.
It’s a fitting literary allusion to a new study of how spiders weave their webs, which is undoubtedly why scientists at Johns Hopkins University referenced Ovid’s story in a recent article published in the journal Current Biology. The JHU team used night vision and artificial intelligence to record every single movement of several hackled-covered ball weavers as they weaved their webs. The experiment revealed that spiders rely on a shared set of movements that amount to “a playbook or web-building algorithm” to create the elegant and geometrically precise structures, even if they have very small brains compared to humans.
Co-author Andrew Gordus, a JHU behavioral biologist, said he was inspired to take the project while he was out birding with his son and saw a particularly spectacular spider web. “I thought, ‘If you went to a zoo and you saw a chimpanzee build this, you’d think it’s an amazing and impressive chimpanzee.'” Gordus said. “Well, that’s even more surprising because a spider’s brain is so small and I was frustrated that we didn’t know more about how this amazing behavior occurs. Now we’ve defined the whole choreography for building the web, which we don’t. was ever made for any animal architecture to this end of a resolution. “
In addition to being aesthetically striking wonders of nature, spider webs form a kind of physical record of many aspects of a spider’s behavior, according to the authors. Gordus and his colleagues thought they could quantify the weaving behavior of spheres, since the process of building a web can be easily defined by both the trajectory of a spider and the geometry of the web.
There are many different species of ball-weaving spiders, but the JHU team chose to work with Uloborus diversus. The team has chosen U. diversus because it stays active all year round and is also conveniently small. The samples were collected in Half Moon Bay, California and housed in a campus greenhouse. There, the spiders ate the fruit flies once a week. Only adult female spiders have been used, as adult males rarely build webs.
For the actual experiments, the team designed a plexiglass arena in the lab, lined with paper at the edges to encourage networking, and equipped with infrared cameras and infrared lights. (U. diversus is a nocturnal spider, with a preference for building horizontal webs in the dark.) Then the researchers moved six spiders to the arena and recorded the spiders each night weaving their webs for an average of 24 hours.
This activity usually followed a well-defined progression. The spider begins by exploring space before building a protoweb that will not be part of the final structure. Think of an artist producing a rough preliminary sketch. Protowebs are quite disorganized and there are long irregular pauses in the spider’s activity as it builds its protoweb, sometimes up to eight hours, because you can’t rush inspiration.
“This state of network construction is thought to be an exploratory phase in which the spider evaluates the structural integrity of the surrounding environment and identifies anchor points for the final web,” the authors wrote.
Next, the spider moves on to building the spokes and the frame for the spider web. “The construction of the loom is often the result of anchoring the silk to the periphery before returning, and then walking outward along a previous ray, anchoring the silk of the loom to the end of the line and then returning to the center,” the authors wrote.
Once the spokes and frame are in place, the spider moves on to building an auxiliary spiral, which takes only a few minutes. Scientists think this phase helps stabilize the structure before the spider builds the final capture coil, as the auxiliary coil is temporary. The spider usually knocks down the web once it is complete. Once the capture spiral is complete, the spider crouches on the hub, sometimes for several days, patiently waiting for prey to become trapped in its web.
The researchers were able to track millions of individual leg movements by designing their own computer vision software for that purpose. “Even if you record it on video, there are many legs to monitor, for a long time, through many individuals”, co-author Abel Corver said, a graduate student studying web-making and neurophysiology. “It’s just too much to go through each frame and jot down the leg points by hand, so we trained the computer vision software to detect the spider’s posture, frame by frame, so we can document everything the legs do to build a whole network “.