How Do Spiders Capture Big Prey?

Live Science

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.

Transcript

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

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