This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
"Charlotte's Web," the E.B. White childhood classic, ends with Wilbur the pig eagerly waiting for Charlotte's baby spiders to emerge from their egg sac. When they finally crawl out, they do something that seems pretty amazing to anyone not familiar with how spiders travel long distances: they fly away. Here's the passage from the last chapter, "A Warm Wind."
A warm draft of rising air blew softly through the barn cellar. The air smelled of the damp earth, of the spruce woods, of the sweet springtime. The baby spiders felt the warm updraft. One spider climbed to the top of the fence. Then it did something that came as a great surprise to Wilbur. The spider stood on its head, pointed its spinnerets in the air, and let loose a cloud of fine silk. The silk formed a balloon. As Wilbur watched, the spider let go of the fence and rose into the air."Good-bye!" screamed Wilbur. "Where do you think you're going?"
But the spider was already out of sight.
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Charlotte's hatchlings were 'ballooning,' which is the method that baby spiders use to disperse themselves through nature. Adults sometimes balloon as well. Curious about the phenomenon, I wrote to Richard Bradley, an entomologist who studies spiders at Ohio State University, for some advice on how to spot a ballooning spider in the wild. Here's his reply:
Ballooning can occur whenever the weather is right, even in summer. It is actually most frequently observed in the autumn around here [Marion, Ohio].The key is weather. You need a relatively calm air or a slight breeze, ballooning doesn't happen often in wind. The rising air currents created by the sun heating the ground are the launching force for these tiny flights. In my experience a calm relatively cool early morning with strong sun is best. Then go to exposed places with prominent launch pads. Small bushes, stumps, fences or fence posts are frequently best.
That is the good news. The bad news is that it is a hit-and-miss proposition to actually find ballooning spiders. The ones that use this technique are often very tiny. On cool clear mornings, if you see silk lines on the foliage or fences of a park (such as Central Park in NYC), watch closely at the uppermost tips of the fence posts. On occasion there will be a field (even an infrequently mown lawn) with lots of small webbing or silk that is visible, particularly on a dewy morning. If you find this, you might be in for a treat. Sadly, it isn't that easy to observe.
Adults of small spiders may balloon, so it isn't always spiderlings (a precious word that arachnologists use for "baby spiders"). I've seen fair sized adults use this technique, but that is less common. It (the phenomenon of ballooning spiders) does occur everywhere.
Good luck, I'd love to hear if you have any success.
Same here. I will be doing my best this summer to catch some ballooning on camera. If you do the same, please share what you've observed.
In the meantime, here are some other spider and ballooning resources:
A vivid account of ballooning by Ohio naturalist and blogger Jim McCormac
"What Are Spiders?" by Richard Bradley