Saturday, 21 January 2012

Spiders



The other day, I walked into a dark room, holding a pair of shoes, and switched on the light as I went through the doorway. I then proceeded to leap a metre into the air and emit a bloodcurdling shriek, because hanging from the shoes, swinging alarmingly close to my body, was an amused-looking spider. It had obviously been hanging in the darkened doorway, waiting to ambush me as I walked through.

I mention this not because it was an unusual occurrence, but precisely because it was not. For several months now, I have been haunted by spiders. It seems that I cannot go into a room without coming face-to-face with one or nearly stepping on one. I was rollerblading recently, and a millisecond before I whizzed past a tree, I suddenly realised I was about to whizz right through a vast, sticky spiderweb, with a big, fat, yellow-and-black spider crouching in the middle of it. Too late. I had whizzed through, and I was trailing a line of spiderweb from my hand, with this monster marching up it towards me. I flapped and flailed, I thrashed and twisted and writhed, and I very nearly lost my balance and ended having my second rollerblading accident. (The first one left me with a broken ankle – but I was a teenager then, and such silliness was pardonable.)

There is a spider that lives in my bedroom. Its station is the corner where the wall meets the ceiling,  and for a long time, I thought it was dead, because it never moved. Then one day, I was rather surprised to find it suspended several centimetres from the ceiling. The next time I looked, it was back at its station. Once in a while, it does that – just hangs for a while, and then goes back – and on rare occasions, it even goes for a walk. I’ll come in to find it thirty centimetres or so to the left. But it always returns to its perch.

I don’t mind its living there. It’s been there for long enough to reassure me that it doesn’t plan to try and crawl into my mouth while I am asleep. (Not that it would. That statistic about eating eight spiders a year in your sleep is a myth. Quite apart from the fact that a spider crawling into your mouth would almost certainly wake you, and you can’t swallow while you’re asleep in any case, why would a spider even try to do that? Would you crawl into a predator’s mouth?)  

My spider-haunting isn’t confined to home territory. They follow me on holiday too. I had a recent holiday disturbed by two spiders – one small and innocuous but clearly looking to get itself dispatched to the big spiderweb in the sky by promenading around the floor in a fearless manner, and one big, ugly one which had in fact managed to get itself thoroughly squashed.

I wish they would leave me alone, but I acknowledge that they need a place to walk around and spin their webs, and if that place happens to be where I’m trying to get on with my life, it’s not their fault. So I don’t kill them. I just cajole them into climbing onto a piece of paper, and then, as they are marching across it, thinking what a very fine surface it is to be walking on, whoops! they find themselves being tossed out a window. I sometimes wonder what they do when they discover that they are outside. Do they go into a blind panic? Do they grieve for their lost home? Do they go looking for friends? Do they just take it in their stride, and accept wherever they are as their new home, and go off to build a new web?

Time for some Spider Facts. (They all come from that great junk heap that is the internet, so feel free to take them as seriously or as lightly as you wish.) I’ll spare you pictures, in case you’re one of those sensitive souls.

1) SPIDER SILK

A)   TYPES
All spiders produce silk, although not all of them weave webs. They can produce up to seven different types of silk, using seven different glands:
1)    Swathing silk, for wrapping and immobilising prey
2)    Egg sac silk, for protecting eggs
3)    Dragline silk (strong), a non-sticky silk, used for parts of the web (so the spider can walk on its web without getting stuck) and as a safety line, in case the spider falls
4)    Dragline silk (weaker) – as above
5)    Attaching silk, used to glue a thread to a surface or to another thread
6)    Sticky silk – core fibres
7)    Sticky silk – outer casing for the parts of the web which will catch prey

B)   REMARKABLE PROPERTIES

Spider silk is extremely tough. Some types of silk are five times stronger than steel of the same diameter – almost as strong as Kevlar, the toughest man-made polymer. It has been suggested that a Boeing 747 could be stopped in flight by a strand of silk as wide as a pencil.

Spider silk is also very elastic, and some types can be stretched to 2-4 times their original length before breaking. 

2) WEB-BUILDING

You know when you walk between two trees, only to find that a spider has spun a web across the gap and you are now swaddled in sticky threads? And then you find yourself wondering how the spider manages to  get from one tree to the other – to lay the foundations, as it were? Well, wonder no more.

The spider does not leap, Spiderman-style, from Tree A to Tree B. Rather, being a resourceful and patient creature, it sits on Tree A and lets down a sticky thread, then waits for the gentle breeze to blow this thread gracefully across to Tree B, where it sticks.

For the rest of the web-building process, I recommend this excellent David Attenborough video.

The spider has to carry out constant maintenance work on its web, because the sticky threads lose their stickiness after a day or so. The spider eats the old threads, so it can recycle the protein.

3) SPIDERGOATS

Researchers have genetically engineered goats to produce silk proteins in their milk. The protein is then extracted and made into a material ten times as strong as steel. Scientists hope one day to develop a way of replacing the keratin in human skin with spider’s silk, which will make the skin bulletproof.
  
4) HUNTING METHODS

a) Fishing
Fishing spiders can walk on water. (Courtesy of surface tension. Don’t bother to try – you’re too heavy.) Video

b) Ant-mimicking
Some spiders take on the appearance and behaviour of ants, so they can move among their prey unnoticed. Video

c) Jumping
Jumping spiders leap at their prey. Video
(I love this introduction to “Jumping Spiders” from About.com:
Can you imagine what it's like to have eight eyes, eight legs, and the ability to jump fifty times your height in distance? If so, then you might have an idea of what it's like to be a jumping spider.

Jumping spiders are charming creatures, which when approached will turn and look at you. If you move, they often follow you with their gaze, changing body angles so as to always keep you well within the sight angle of one of their eight eyes.)

d) Hunting on the ground
Wolf spiders stalk their prey on the ground.

e) Building trapdoors
Trapdoor spiders dig a hole and cover it with a silken lid camouflaged with debris. They lay silken tripwires and sit waiting in the hole, then when lunch walks by, they leap out and grab it. Video

f) Ambushing other spiders in their webs
Portias eat other spiders. They hang around the prey’s web and lure it out either by pretending to be a dead leaf (they look a bit like leaves, and spiders don’t have very good eyesight) or by drumming on the web to create vibrations which mimic those of trapped prey or courting males

g) Camouflaging
Some spiders are coloured to coordinate perfectly with certain flowers. They sit on the petals and wait for some unsuspecting insect to come along. Picture 1 Picture 2

h) Casting silk
Gladiator spiders hang head down, dangling a net. When lunch walks by, they throw the net over it. Video 

Spitting spiders squirt a double thread of silk at their prey, immobilising it.

Bolas spiders release pheromones to attract moths, then hurl sticky silk at them. Video 

5) LUNCH

Once a spider has captured its prey, it injects enzymes into the unfortunate creature’s body, then leaves it to marinade for a while. The enzymes turn the prey’s insides liquid, and the spider then sucks the liquid out, much in the manner of a small child hoovering up a milkshake.

If you are a gentleman spider, you may, to your great chagrin, find yourself becoming lunch for your lady friend after you have seduced her – or even, in a show of shocking bad manners, while you are seducing her. It’s a mutually beneficial business (if not necessarily a whole load of fun) - you’re an excellent source of protein, and by feeding her, you prolong the romance, upping your chances of fatherhood.  

6) THE BIGGEST LOAD OF BS ABOUT SPIDERS I HAVE EVER SEEN

which includes such gems as:
“Most household spiders come from the fact that most people don't properly wash their new clothing after purchase. 90% of clothing purchased at retail stores contain spider eggs laid during shipment”

and

“The most valuable spider is the Kenyan Applecrosser. These elegant spiders actually grow beautiful, near-flawless emeralds on their abdomens.”

SO, WHAT HAVE WE LEARNT?

1) You probably haven’t eaten a spider in your sleep, so stop that tiresome fretting.
2) Jumping spiders are charming creatures. Seriously. And they watch you, which is just unbearably cute.
3) Spider meals are a diverse but always complicated affair, which may be why spiders are not known for their convivial dinner parties.
4) Spider silk, in collaboration with goats, may one day make you bulletproof.
5) David Attenborough is the closest thing to a walking encyclopaedia that you are likely to find.

SOURCES
(I do recommend following some of these links. They are incredibly interesting.)

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