The latest viral spider news is horrifying at face value: Residents of North Memphis, Tenn., were treated to an unexpectedly white Thanksgiving when a spider web at least half a mile long appeared on the grass.

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report that "millions" of spiders are on the scene, with residents desperate for the town to take action.

At first glance this may just look like frost on the ground, but it's actually millions of spiders showing out in one Mid-South neighborhood. >>http://shout.lt/bj6ks

Posted by WMC Action News 5 on Monday, November 23, 2015

"I've seen about 20 on my porch just in the last day," a resident named Ida Morris told WMC Action News 5. "Clean this area up and spray for these spiders and make it safe. There are kids running around. A spider could bite the kids or anything."

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Slight discomfort with a sudden swarm of spiders is understandable, to say the least. But there's no cause for concern. It's an example of what's called a "ballooning" event, where tiny juvenile spiders try to float off and make their way in the world.

"These ballooning events are quite common," Susan Riechart, a professor at the University of Tennessee Knoxville and former president of the American Arachnological Society, told The Post. In fact, Riechart said, she's spotted a few recently in her own county. She believes the particularly warm weather this fall may have triggered some dispersals.

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"Young juvenile spiders of most families disperse by sending out a swath of silk threads that may be over a meter in length," Riechart explained. "Particular air currents favor ballooning. This would explain the fact that thousands to hundreds of thousands may take off at the same time. Caught by the air currents, the spiderlings have no control over where they will land, but it is not surprising that they may fall in the same area."

That's why it's quite common for areas to become swathed with webbing, as wind currents send local spider babies all tumbling into the same patch of grass. The same spiders and their parents have probably been sitting in nearby fields unnoticed for ages.

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Riechart couldn't identify the spiders based on images, but said they were definitely nothing to worry about.

"Totally harmless," she said. "Without mouth parts that would even be large enough to pierce our skin."

No skin piercing means no biting — and that's the only way a spider can cause any harm to a human.

The event is a sign that all systems are go, ecologically speaking, in the Memphis area. Come spring, residents will be glad for their local spiders, which eat huge quantities of pests like mosquitos and insects that prey on crops. That's probably little consolation when tiny spiders keep flying onto your porch, but hey: Nature is rarely convenient.

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