When a National Park Service building in Southeast Alaska started growing fur, it appeared to be something straight out of a B-rated Sci-Fi flick featuring the Wolf Man. Upon closer investigation, things got even creepier.

“At first it appeared that to celebrate #Halloween our admin building was sprouting hair,” wrote park officials in an online post. 

Arachnophobes beware: this is about to get dicey. The fur-like strands turned out to be moving, living… legs. And not just any legs. Hundreds of creepy, crawly limbs belonging to a spider-looking creature, the daddy long-legs. Across social media, the photos have been shared thousands of times with equal amounts of intrigue and disgust. It’s easy to see why – it actually looks like long, coarse, brownish-black hairs are growing out of the building's cracks.

But look closely and you can actually see the tiny circular bodies holding each set of eight legs together. We had to know: Is this type of phobia-inducing cluster behavior all that common? Apparently, yes.

“They might cluster together like this for protection or for hunting, but the effect is impressive and perfect for this day,” wrote Glacier Bay National Park in a Facebook post.

An Opiliones by any other name (including harvestmen, shepherd spiders, and grandfather graybeards) is not actually a spider, even though they resemble arachnids. Mostly active at night, the harvestmen are seen in large clusters during the fall (right around harvest time) during the day, only to disperse in the hundreds as soon as night falls. Unlike spiders, daddy long-legs don’t have silk spinnerets for weaving webs. Rather, it is an opportunistic hunter that feeds on a variety of prey, as long as it’s small enough to fit in their teeny tiny crab-like mouths, including soft-bodied insects like slugs, snails, leaf beetle larvae, and decaying organic matter. As if that’s not icky enough, they also have special glands for a defense that produces strong-smelling secretions to ward off predators (ew). Oh, yeah, and their eyes are on their backs (WTF?!). 

In all honesty, harvestmen sort of get a bad rap. They cannot bite humans (phew) and actually don’t even produce venom, despite many urban legends saying they are the most poisonous spider in the world. And hey, it’s kind of cute that they all stick together, right?