Sunday 3 November 2013

Darwin's Bark Spider

Image: Matjaz Kuntner
The little monster with the world's most monstrously massive web!

Bark Spiders are a little known group of orb-weavers found across tropical Africa and Asia. Apparently they get their name from the fact that at least some of them look like a bit of bark or dead leaf, which is of course an eminently sensible disguise against predators.

Image: GalliasM
Indeed, it's so sensible, reasonable, uncharismatic and altogether lacking in eccentricity, that scarcely anyone gave the Bark Spiders a second look. They're spiders. A bit like how other spiders are spiders. And that's just not interesting enough in tropical Africa and Asia where there are so many weird, wonderful and gigantic spiders to choose from.

All that changed in 2009 with the belated discovery of Darwin's Bark Spider in the forests of Madagascar. Although, one can't help but think that their handiwork must surely have been noted well before that. It's certainly eye-catching enough.

Video: Matjaž Gregorič
Releasing bridging silk

The thing is, Darwin's Bark Spiders like to build their webs across bodies of water. Standing on one side of a river or lake, they release a thread of silk into the breeze and keep going until it catches onto a twig or leaf on the other side.

Video: Matjaž Gregorič
Lots of bridging silk

Sometimes this requires a paltry 3 metres (10 feet) of silk to cross a narrow stream...

Image: Lalueza-Fox, C.; Agnarsson, I.; Kuntner, M.; Blackledge, T. A.
But for one particular lake, a whopping 25 metres (80 feet) was needed. 25 metres! That's longer than most Fin Whales. And Fin Whales are the second biggest of all the whales.

These mighty bridge lines serve as the frame for the rest of the web, which is suspended beneath. The web proper is traditional with its spokes and spirals, it just happens to be right above a load of water. Also it's HUGE! The biggest take up an area of 2.8 m² (30 square feet), more than any other web in the world.

All this from a spider that's less than 2 cm (0.8 in) long! This is a large spider, but large in the sense of a European Garden Spider rather than a Golden Orb-weaver.

Image: GalliasM
With the sheer size of the web and the fact that its failure would mean falling into a river, it's not surprising to learn that those bridge lines are also incredibly tough. "Tough" here doesn't mean that it can survive the apocalypse with nothing but a spork and a field guide to edible mushrooms. It's actually the term used to describe how much force a thing can withstand before getting torn and smashed. The Darwin's Bark Spider can produce silk twice as tough as any spider silk known thus far, and 10 times tougher than Kevlar.

It's no wonder they look after their webs and make repairs for several days before moving on to make a whole new one elsewhere. If only we could convince them to stay in one place. We could replace all those stupid rope bridges that seem to cause everyone so much trouble. Though I suppose Indiana Jones wouldn't have been able to cut his one so easily, but that's just the price we pay for progress.

These powerful, gargantuan webs naturally catch a lot of prey. One was spotted with 32 mayflies, and the spider gathered them up and wrapped several corpses together in a macabre, silk-covered orgy. Alas, so much meaty fruit hanging on the vine attracts a LOT of flies. They're buzzing around, eating prey that hasn't been wrapped up, eating prey that has been wrapped up... there were ten spotted eating prey the spider was currently eating! No shame and no fear. Some of these good-for-nothing parasites were even new to science! New talent, new hangers-on.

It's strange, these spiders. What must it be like to create your home and means of survival from your own backside? Some day, when we've sorted out the technology to turn our faeces into power, we'll begin to understand.


TexWisGirl said...

wow! that is some engineering feat!

Joseph JG said...

It really is! So impressive!

Unknown said...

I had several pet tarantulas. They were calm and fearful except when feeding. I'd guess that the tarantula in the video saw a small reflection of itself in the lens and attacked what it thought was lunch.

Joseph JG said...

I'm forever surprised at how fearful tarantulas are! They have no idea how terrified they make so many people

Tiggi said...

And now we know what really happened to Jimmy Hoffa...

Joseph JG said...

Wow, I had to look that one up. What a mystery!

Unknown said...

I wish to purchase some Darwin's bark spider silk