A few days ago I wrote about a strange collection of spiders seen at Crex Meadows near Grantsburg, Wis. Stretched along a 150-yard section of refuge road were thousands and thousands of spiders. They were on a sheet of spider silk that looked not like webbing but more like cloudy plastic wrap for food storage. The largest of the spiders would cover a dime. Most were much smaller.

The question was, what was going on? I had never seen anything like it.

I sent photos to a biologist friend. He sent them to Jim Fitzpatrick at Carpenter Nature Center near Hastings. And Jim sent them to his brother, John Fitzpatrick, who runs the Cornell Lab of Ornithology in New York State. John sent them to Mark Deyrup at the Archbold Biological Station in Venus, Florida.

He provided the answer.

I have to note that two days prior, Val Cunningham, who shares with me the birding columnist duties for the StarTribune, also sent me the answer. She found it the old-fashioned way — Google.

The answer is failed mass ballooning. Here’s what Deyrup wrote:

“This … appears to be the result of a mass ballooning event by a number of different species of spiders. This occasionally happens when weather has not been good for spider dispersal. The spiders run up the nearest tall shrub in the open when the weather is dry and breezy and not too cold. They then release threads that (are intended to) carry them away after the threads get long enough. You can see some spiders doing this in the photos. Each spider leaves a thread wherever it goes as they climb the shrub, and many of the threads that are sent out on the breeze end up back on the starting point, so the amount of silk quickly adds up. Sometimes there are so many spiders ballooning that the spiders landing on a field and shrubs cover everything with a delicate layer of silk.”

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