Photo of 'furry' building turns out to be the stuff of nightmares: 'Are you scared?'

Happy Halloween.

A chilling photo of a "furry" building at Glacier Bay National Park and Preserve in Alaska went viral after the National Park Service shared it on Facebook on October 31.

So, why is the photo perfectly appropriate to celebrate the spooky holiday? A closer look reveals the fuzzy area under one of the building's ledges is actually hundreds of daddy long legs.

YIPES.

"These Harvestmen, also called Daddy-longlegs, are arachnids but are NOT spiders," the service explained in its educational yet cursed post. "Harvestmen are in the order, Opiliones, whereas spiders are Araneae. Harvestmen have one basic body section (spiders have two), two eyes, and eight legs. They live in moist habitats and are usually found under rocks, on logs, and in your nightmares."

Truth.

The service went on to explain that Harvestmen clump together in such a terrifying manner as a means of protecting themselves from enemies, which makes sense, because you'd have to be out of your mind to go near that thing.

"A group of harvestmen looks larger and scarier (are you scared?)," it wrote, in the understatement of the century. "So it can cause predators to think twice about disturbing them or having them as a meal."

Ultimately, the National Park Service assured that daddy longlegs "just want to be your friend...or possibly carry you off into the woods..."

"Have a good one!" it ended its post.

Daddy longlegs, while spine-tingling in appearance, are more or less harmless to humans.

Though harvestmen do, in fact, possess fangs strong enough to penetrate human skin, their venom has negligible toxicity on mammals, according to research published in the journal Frontiers in Evolution and Ecology.

On the contrary, harvestmen should really be considered ideal house guests — they tend to dwell in dark, damp places, such as unfinished basements, rarely entering finished areas of a home, all the while feasting on garden pests like spiders and aphids.