Ingenious web construction and energy stored in stretched silk strands lend spiders super powers to lift animals too heavy for the spiders' tiny muscles to support.
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00:00You've probably seen spiders catch insects that are smaller than they are in
00:04their sticky webs. But did you know that there are some spiders that can catch
00:08prey that's much larger than they are? And they do it by wrapping them in sticky
00:13strands of web and lifting them off the ground.
00:20Now scientists have known about this behavior for some time, but it hasn't
00:25been very well studied. So for the first time a group of scientists took
00:29several of these spiders and observed them doing this prey lifting behavior
00:35under laboratory conditions. The spider built this web. In the connection
00:39between the main frame of the web, which is the part dense of threads, and the
00:45surface below, the spider spin these threads. And these threads are actually
00:52the feature that sends signals to the spider that something is hitting, something
00:58is passing below. So the elastic energy stored in the frame, which is basically
01:05we have to think about an elastic, you know. So if you pretension an elastic, it will
01:10recall with an elastic force. If the prey is small, so just one thread is necessary to lift it.
01:16Unfortunately, when the prey is big, of course the one thread is not necessary, but this is what
01:23actually poses a challenge to the spiders. The logic is exactly the same as before. So the spider
01:30produce thread as elastic and it pretensions them. Then it attaches this thread to the prey. And this is pretty cool, because it's one of the few cases
01:42where the spider is actively involved in the hunting by means of the web.
01:48It's no more a trap, a passive trap, in the sense that the web works perfectly as it is, but the spider is getting involved too.
01:56Because normally the spiders are just sitting and waiting for the prey that enters the web. And that's it.
02:03As you can see, the structure of this web is particularly complicated. There are different types of silk.
02:10So each part of the web has its own silk for that specific function. These are the supporting threads.
02:19And as you can see, there are two types of threads. Two threads in these supporting threads. One thread is produced by a gland.
02:26The other one is produced by another gland. The very same thread, but this thread is coated with these droplets that are produced by another type of silk.
02:40And we have three types of silk. Where the spider joins together these threads, it uses this kind of cement-like silk, which is another type of silk.
02:51Four different types of silk are used to produce this frame. It also wraps the prey because it has also to mobilise locally the prey in order to avoid the prey to move too much.
03:03And it uses another type of silk to wrap it. Normally material scientists go crazy with this because the spider is a perfect factory of silk.
03:13It produces multifunctional materials in less than milliseconds. Each one optimise for that property. So it's crazy. They are like machines. They are super efficient.
03:27And there are like 49,000 different species of spider. Each one produces different type of silk with different properties up to the species, up to the individual. So basically we do not know nothing about silk.
03:41When you do start studying in depth things, you realise that you don't know anything about them. And I don't know, we use two species of spider.
03:49There are other species of spider, as I said before, that must be investigated from this point of view. There are also other types of prey that may behave differently.
03:59So this was just the first insights in this direction, but there are tons of possible questions that can be answered.
04:08So even though scientists now have a better idea as to how the spiders are able to trap large prey and actually lift it up off the ground,
04:18there are still a lot of unanswered questions about how exactly the spiders make all these different types of silk,
04:25and what are the limits of how they can use them?
04:29Transcription by CastingWords