Hikers prodded what looked like a hibernating animal in a cave - only to find it was a nest full of thousands of spiders.
Two young walkers were near the town of Alamos in the north-western Mexican state of Sonora.
They then came across what looked like a small furry creature sleeping in the corner of a cave
One hiker can be heard saying: "I don't know what it is but it's very hairy! Is it a sleeping animal?"
The curious pair then decided to poke the creature with a stick.
But they were clearly shocked to discover it was not one mammal but several thousand arachnids.
Later identified as pholcidae, commonly known as cellar spiders or daddy longlegs, they poured out of the nest as they realised their hiding place had been disturbed.