|This entry is dedicated to…|
|Marme, the only entomologist I know|
|Beth, who slept with a bl**dy barn spider over her bed|
Spiderwebs fascinate me. They're elegant, ingenious, and horrifying, really.
The Washington Avenue Bridge has a pedestrian walkway with railing to prevent one from inadvertantly falling off. These railings have vertical bars every six or so inches, larger supporting bars less frequently, and street lamps breaking through railings and all maybe every forty feet.
The space between each bar contains at least one spider web, and at least one spider. Therefore, there are hundreds and hundreds of spiders. Walking across the bridge one night, I found one of the Master Spiders weaving its web.
I like to think that the spiders have some sort of hierarchy. Only those who build the best and most glorious of webs are allowed to take the honoured, but hazardous, space between a lamp-post and the top of the railing. All the other spiders must cluster with their smaller webs in the spaces between bars and up around the lights. These talented few are the Master Spiders, and spin the largest webs.
The Master Spider had already finished the web's top supporting strand. This stuff, known as dragline silk, is as strong as steel, with a tensile strength of ~1500MPa. The supporting line stretched a good four feet and, at the ends, was anchored to the railing and lamp-post with a splaying collection of dozens of smaller fibers. A few of the capture-spiral lines were already in place, their strength similar to that of the dragline, but able to stretch more - up to 1.4x their relaxed length.
As I watched, the spider began making its slow spiral inwards, leaving an infinitesimal trail behind. A strand of silk long enough to encircle the planet would weight less than a pound.
The strongest spider silk averages 350 MJ/m3 with an upper limit of 520 MJ/m3, over 10x stronger than Kevlar; so, you can imagine the potential for commercial application.
Yet it isn't easy. The silk starts as a protein liquid produced by hundreds of glands which the spider packs into formation. Alas, spiders tend to kill each other if confined, so they can't be housed together and farmed for silk. So difficult, in fact, is the process, that only a single piece of fabric made from spider silk exists in the world. At eleven by four feet, the cloth took eighty-two people four years to construct using silk from over one million golden orb spiders in Madagascar (named for the distinctive colour of their silk). Each spider contributed about eighty feet of silk, extracted using a specialised silking machine. After their "donation", the spiders were released back into the wilds.
The final piece weighed in at about 2.6 pounds, about 24,000 spiders' donations per ounce, and it's beautiful.
But that work could never be reproduced economically. So other approaches have been tried: genetically altered goats. Yes, goats. Produced in 02000, their milk contained 1-2 grams of silk protein per liter. Imagine… spider goats.
Another attempt has been genetically modified silkworms: less terrifying than goats, but still not as strong as the original.
Wanting to capture the background a bit more, to give a sense of location to these photographs, I tried out a different technique.
And it was while I was working on this that excitement happened.
And, by that time, it had grown late… so I wandered on, leaving molecular mysteries and predatory horror behind.