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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00:00 You've probably seen spiders catch insects that are smaller than they are in their sticky webs.
00:05 But did you know that there are some spiders that can catch prey that's much larger than they are?
00:10 And they do it by wrapping them in sticky strands of web and lifting them off the ground.
00:17 [music]
00:21 Now scientists have known about this behavior for some time, but it hasn't been very well studied.
00:26 So for the first time, a group of scientists took several of these spiders
00:31 and observed them doing this prey lifting behavior under laboratory conditions.
00:37 The spider built this web.
00:38 In the connection between the main frame of the web, which is the part dense of threads,
00:45 and the surface below, the spider spins these threads.
00:50 And these threads are actually the feature that sends signals to the spider
00:55 that something is hitting, something is passing below.
01:00 So the elastic energy stored in the frame, which is basically, we have to think about an elastic, you know,
01:07 so if you pre-tension an elastic, it will recall with an elastic force.
01:12 If the prey is small, so just one thread is necessary to lift it.
01:16 Unfortunately, when the prey is big, of course the one thread is not necessary.
01:23 But this is what actually poses a challenge to the spiders.
01:27 The logic is exactly the same as before.
01:29 So the spider produces threads as elastic and it pre-tensioned them.
01:35 Then it attaches this thread to the prey.
01:39 And this is pretty cool because it's one of the few cases where the spider is actively involved in the hunting by means of the web.
01:48 It's no more a trap, a passive trap, in the sense that the web works perfectly as it is.
01:54 But the spider is getting involved too.
01:57 Because normally the spiders are just sitting and waiting for the web, for a prey that enters the web.
02:03 And that's it.
02:04 As you can see, the structure of this web is particularly complicated.
02:08 There are different types of silk.
02:11 So each part of the web has its own silk for that specific function.
02:18 These are the supporting threads.
02:19 And as you can see, there are two types of threads.
02:22 Two threads in these supporting threads.
02:24 One thread is produced by a gland.
02:27 The other one is produced by another gland.
02:30 They are very same threads.
02:33 But this thread is coated with these droplets that are produced by another type of silk.
02:40 And we have three types of silk.
02:42 Where the spider joins together these threads, it uses this kind of cement-like silk, which is another type of silk.
02:50 So four different types of silk are used to produce this frame.
02:56 It also wraps the prey because it has also to mobilize locally the prey in order to avoid the prey to move too much.
03:03 And it uses another type of silk to wrap it.
03:07 Normally, material scientists go crazy with this because the spider is a perfect factory of silk.
03:13 It produces multifunctional materials in less than milliseconds, each one optimized for that property.
03:21 So it's crazy.
03:23 They are like machines.
03:25 They are super efficient.
03:27 And there are like 49,000 different species of spider.
03:33 Each one produces different type of silk with different properties up to the species, up to the individual.
03:39 So basically, we do not know nothing about silk.
03:41 When you start studying in-depth things, you realize that you don't know anything about them.
03:46 And I don't know, we use two species of spider.
03:49 But there are other species of spider, as I said before, that must be investigated from this point of view.
03:54 There are also other types of prey that may behave differently.
04:00 So this was just the first insights in this direction.
04:03 But there are tons of possible questions that can be answered.
04:09 So 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,
04:18 there are still a lot of unanswered questions about how exactly the spiders make all these different types of silk.
04:25 And what are the limits of how they could use them?
04:29 [MUSIC]