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 their sticky webs.
00:05But did you know that there are some spiders that can catch prey that's much larger than they are?
00:10And they do it by wrapping them in sticky strands of web and lifting them off the ground.
00:21Now, scientists have known about this behavior for some time, but it hasn't been very well studied.
00:26So, for the first time, a group of scientists took several of these spiders
00:31and observed them doing this prey lifting behavior under laboratory conditions.
00:37The spider built this web.
00:38In the connection between the main frame of the web, which is the part dense of threads,
00:45and the surface below, the spider spins these threads.
00:50And these threads are actually the feature that sends signals to the spider
00:55that something is hitting, something is passing below.
01:00So, the elastic energy stored in the frame, which is basically, we have to think about an elastic, you know.
01:07So, if you pretension an elastic, it will recall with an elastic force.
01:12If the prey is small, so just one thread is necessary to lift it.
01:16Unfortunately, when the prey is big, of course, that one thread is not necessary.
01:23But this is what actually poses a challenge to the spiders.
01:27The logic is exactly the same as before.
01:29So, the spider produced thread as elastic and it pretensioned them.
01:35Then it attaches this thread to the prey.
01:39And 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.
01:48It's no more a trap, a passive trap, in the sense that the web works perfectly as it is.
01:54But the spider is getting involved too.
01:57Because normally the spider are just sitting and waiting for the web, for a prey that enters the web.
02:03And that's it.
02:04As you can see, the structure of this web is particularly complicated.
02:08There are different types of silk.
02:11So, each part of the web has its own silk for that specific function.
02:18These are the supporting threads.
02:20And as you can see, there are two types of threads.
02:22Two threads in these supporting threads.
02:24One thread is produced by a gland.
02:27The other one is produced by another gland.
02:30They are very same threads.
02:33But this thread is coated with these droplets that are produced by another type of silk.
02:40And we have three types of silk.
02:42Where the spider joins together these threads, it uses this kind of cement-like silk, which is another type of silk.
02:50So, four different types of silk are used to produce this frame.
02:56It also wraps the prey because it has also to mobilize locally the prey in order to avoid the prey to move too much.
03:03And it uses another type of silk to wrap it.
03:07Normally, 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 optimized for that property.
03:21So, it's crazy.
03:23They are like machines.
03:25They are super efficient.
03:27And there are like 49,000 different species of spider.
03:33Each one produces different type of silk with different properties up to the species, up to the individual.
03:39So, basically, we do not know nothing about silk.
03:41When you start studying in-depth things, you realize that you don't know anything about them.
03:46And, I don't know, we use two species of spider.
03:49But there are other species of spider, as I said before, that must be investigated from this point of view.
03:54There are also other types of prey that may behave differently.
04:00So, this was just the 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 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.
04:30NASA Jet Propulsion Laboratory
04:32California Institute of Technology