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 several
00:30of these spiders and observed them doing this prey-lifting behavior under
00:35laboratory conditions. The spider built this web. In the connection between the
00:39main frame of the web, which is the part dense of threads, and the surface below,
00:46the spider spin these threads. And these threads are actually the feature that
00:53sent signals to the spider that something is hitting, something is passing below.
00:59So the elastic energy stored in the frame, which is basically, you have to think
01:06about an elastic, you know. So if you pretension an elastic, it will recall with
01:11an 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
01:24actually 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
01:39pretty cool because it's one of the few cases where the spider is actively involved in the hunting
01:47by means of the web. It's no more a trap, a passive trap, in the sense that the web works perfectly as
01:53it is, but the spider is getting involved too. Because normally the spiders are just sitting and
01:59waiting for the prey that enters the web. And that's it. As you can see, the structure of this web is
02:06particularly complicated. There are different types of silk. So each part of the web has its own silk
02:15for that specific function. These are the supporting threads. And as you can see, there are two types of
02:21threads, two threads in these supporting threads. One thread is produced by a gland. The other one is
02:28produced by another gland. The very same thread, but this thread is coated with these droplets that are
02:37produced by another type of silk. And we have three types of silk. Where the spider joins together these
02:44threads, it uses this kind of cement-like silk, which is another type of silk. So four different types of silk
02:53are used to produce this frame. It also wraps the prey because it has also to mobilise locally the
03:00prey in order to avoid the prey to move too much. And it uses another type of silk to wrap it. Normally
03:08material scientists go crazy with this because the spider is a perfect factory of silk. It produces
03:14multifunctional materials in less than milliseconds, each own optimised for that property. So it's
03:22crazy. They are like machines. They are super efficient. And there are like 49,000 different
03:31species of spider. Each one produces different type of silk with different properties up to the
03:37species, up to the individual. So basically we do not know nothing about silk. When you do start
03:43studying in-depth things, you realise that you don't know anything about them. And I don't know, we use
03:48two species of spider. There are other species of spider, as I said before, that must be investigated
03:53from this point of view. There are also other type of prey that may behave differently. So this was just
04:00the first insights in this direction, but there are tons of possible questions that can be answered.
04:09So even though scientists now have a better idea as to how the spiders are able to trap
04:14large prey and actually lift it up off the ground, there are still a lot of unanswered questions about
04:22how exactly the spiders make all these different types of silk and what are the limits of how they can use them.