This morning I walked out my front door to go to work and I nearly walked into a three-foot-diameter web with a big ugly spider in the middle of it. Somehow this spider managed to suspend its web from a bush (to the left and up about six feet away), to the eave of my roof (directly above about five feet), and to a tree (to the right and up about ten feet from the ground). The web itself was suspended in the center of all three supports. I can see how the spider could suspend the web from the roof, but how in the heck did it get across to anchor its supports to the tree and the bush? Can these spiders fly?
-- Matt, the net
Gack! That's all we'd need. Flying spiders. Actually, they're more like base jumpers, though in the spider biz it's called ballooning. Did I ever tell you about the big spider attack at the classy Alice wedding we went to? We're all out on the big lawn under the big oak trees. We're all propped up on those tiny rental folding chairs designed for people with liposuctioned butts. We're all waiting something to happen, like the bride and groom to show up. Instead, about a jillion spiders, in unison, dropped down on us from the tree limbs on tiny silk threads. Oh, the screaming, the hysteria! Everybody grabbing their wedding presents and heading for their cars. Grandma and I thought it was part of the ceremony, like some weird twist on the traditional release of doves. Turns out it's actually just a common method of spider travel, dropping from a great height on a thread of silk.
Your garden spider (they're big and ugly, the most likely candidate), ready to build his web, waited in the tree for the wind to be just right, then anchored one end of the silk to the tree and stepped off into the void. When he ballooned on the wind into your eaves or the bush or whatever he hit first, he anchored the other end of the silk, and he was home free. He could tightrope back up to the tree on the anchored line or strike off in another direction, depending on the circumstances. Spiders can't see very well, but they're very sensitive to vibration and wind.
Web of Lies
Re: Our answer about how a big, fat garden spider, bungee-jumps on a thread of silk ("ballooning") to connect a tree to some lower structure. Frequent spider-watcher Al Collins offers this amendment. "The amount of wind necessary to carry one of the larger species would be very strong. What they do is even simpler. From his perch, the spider lets out a single strand of silk, which is carried by the wind. When he feels it hit something and stick, he reels in the excess, making it taut, then climbs down the strand to continue building the web." Al's actually seen this happen. We can't argue.