THIS is the nightmare moment a man picks up a bizarre looking "furball" in his back yard just as it transforms into hundreds of creepy crawlies.
In the terrifying clip - which was apparently shot in Texas - the man is seen reaching out to the mystery mass in the corner of a garden wall.
However, as he carefully cradles the throbbing creature in his hands it starts to suddenly break apart quickly revealing what it is really made up of.
Within microseconds thousands of Harvestmen - daddy longlegs - are seen making a panicked dash to safety.
Just as the Instagram clip ends the shocked man is seen shaking the remaining bugs off his hands.
Many of those to have seen the footage - which was uploaded on Saturday - say it really made their skin crawl.
One viewer said: "I screamed at this" while another added: "I wish I hadn't watched this just before I went to bed!"
Why do Harvetsmen form into bizarre clusters?
Although Harvestmen - or daddy longlegs as they are often called - are arachnids they are not actually spiders.
They gather in huge groups, which look like hairy clumps due to the closeness of their many legs.
The animals interlock their spindly legs as they cluster together to provide the warmth they need to thrive.
While together they excrete chemicals that give them a "distinct, unpalatable smell."
It's also believed the bizarre bug clusters are part of a "safety in numbers" defence mechanism.
The clusters sometimes jiggle or move from one place to another as one to confuse predators.
However, experts say despite their looks the bugs are completely harmless.
Harvestmen are arachnids but not spiders, explained Prashant Sharma, a scientist at the American Museum of Natural History.
There is a long-running myth they are venomous, however no known species possesses venom glands - unlike spiders which can.
Sharma said: "When some species are disturbed, like the ones shown in the video, they rock up and down in a rhythmic, undulating motion.
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"While a large group of them does this together, the effect is disturbing" to other animals.
According to the RSPB, a harvestman catches its insect prey by using hooks on the ends of its legs and defend themselves by secreting a foul-smelling fluid.
If they are captured, they are able to shed a leg to escape.