David Freiheit was amazed to see large, dark clusters of tent caterpillars on some trees in his local dog run in Montreal, Canada. He theorized that the caterpillars were likely pupating, creating pupae to then transform into butterflies.

David returned to the park five hours later, and saw that the caterpillars had moved into a line formation, moving up the tree. David and his young daughter were intrigued by the weird sighting, which David described as “beautiful and horrifying”. Credit: Viva Frei via Storyful