A Danish scientific journal asked an entomologist how spiders manage to weave such large webs. It turns out that they are real masters of engineering: spiders not only work daily on complex structures, but also come up with the most cunning and insidious traps.
Our reader Susanna went for a walk in the forest. Walking through the woods, she fell face-first into a cobweb - with whom has not happened, but brrr!
Susanna looked around and saw that a large spider had weaved a web across the path, and between the trees at a distance of several meters from each other.
This got Susanna thinking about the spider's impressive engineering work, and when she returned home with her hair full of cobwebs, she immediately rushed to the computer.
"How do spiders weave such a big web?" - asked Susanna in a letter to the heading "Ask Science" (Spørg Videnskaben).
Spider web is carried by the wind
To answer the question, we turned to Sebastian Frische, professor at the Institute of Biomedicine at the University of Aarhus.
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Sebastian Frische investigates exclusively the web, and he explained to us that the spider begins to weave its web (if it is a circular web - but more on that later) from one thread, which is called a "web bridge".
For example, when a spider needed to weave a net across the path along which Susanna was walking, he sat on the branches on one side of the path, healthy upside down with a piece of silk thread.
He waited for the wind to pick up the thread and pull it farther and farther, until it anchored on some branch on the other side of the path.
This is how the first "bridge" stretches over long distances.
“When spiders fly, they do the same. They let the wind pick up a piece of the web, and then release the branch on which they sit. In this way, spiders can fly many kilometers,”says Sebastian Frische.
Weave a web without glue
When the first thread was pulled across the path, the spider reinforced it with more threads. And only after that he began to weave the frame, which eventually became the outer edge of the web.
The spider starts by pulling a thread from the middle of the "bridge" to an anchor point - it could be some other branch - and then connects three points with threads, forming a triangle.
Having created the frame, he begins to stretch the "spokes" from the middle of the net to the edges, like a bicycle wheel.
Then it forms a stabilizing spiral from the middle of the net to the edges - across the "spokes".
“So far, the spider has used a completely normal type of silk web, without any glue. All this is needed to create a rigid frame for the web, with the help of which he will catch insects,”says Sebastian Frische.
Different spiders weave different webs
Having created a stable base for its web, the spider crawls into its middle and begins to weave a spiral of sticky silk from the center to the edges.
The spider steps carefully so as not to touch the sticky threads: it goes only along the usual ones. Otherwise, he himself may get stuck.
Along the way, the spider removes the temporary spiral until only the sticky spiral and non-sticky stabilizing "needles" remain on the web.
Finally the spider settles in the center and pulls the threads here and there a little to create the correct tension throughout the net.
Here's a spider web and ready to catch flies - or Susanna.
“Usually the spider sits in the center of the web, waiting for a fly or something like that to hit it. But some spiders sometimes sit to the side, holding one paw on a "signal thread" that twitches if someone is caught in the net. Different types of spiders behave differently, "explains Sebastian Frische.
The crosses weave a new net every day
The most common Danish spider spends an hour and a half in the morning to weave a net with a diameter of about 20-30 centimeters.
However, the net quickly breaks, and after a day the spider has to rewind the sticky part.
Other spiders weave webs in the evening to catch insects at night or in the morning.
The prey is wrapped in a third kind of web
Spiders use different types of webs for different purposes. We have already mentioned sticky and non-sticky threads, but there is a third variety.
If someone gets caught in a spider web, the spider crawls to the prey and wraps it around it with a completely different - the third type of web. This time, he uses many thin threads, which he releases very quickly - before the prey escapes.
“These are special silk threads, their advantage is that the spider can cover a large area with them in a short time,” says Sebastian Frische.
Well, then, unfortunately for the caught insect, the spider quickly bites it and pumps it up with poison. The venom contains enzymes that slowly dissolve the prey so that the spider can suck it out like an egg from its shell.
Throwing cobwebs at prey
Different types of spiders use their webs differently.
Bolas spiders use the net as a throwing weapon.
When a bolas wants to catch a prey, it releases a long thread with a lump of glue at the end.
He swings a ball of glue around, trying to hit, for example, a night moth, and if he succeeds, he pulls the victim to him and wraps it in a web, as if wrapping a lunch box in paper.
Making web traps
There are no bolas spiders in Denmark, but there are other types of spiders (steatodes) that weave so-called glue traps - no less impressive.
The glue trap consists of a horizontal web of cobwebs about five centimeters above any surface. Between the canvas and the surface, the spider pulls several thin threads with a lump of glue at the base.
If, for example, an ant goes under the net and touches one of these threads, the trap will work - the thread with a lump of glue in which the ant is stuck will rise up and it will be suspended.
“It will hang out there until the spider arrives,” explains Sebastian Frische.
Kristian Sjøgren