European Peacock Butterfly Aglais io

Those four enormous eyespots are not just for decoration. When threatened, this butterfly snaps its wings open and simultaneously produces a loud hissing sound by rubbing its wings together — the sudden combination of giant "eyes" and an unexpected noise is enough to send startled birds fleeing. The anti-predator display is one of the most studied in any insect. Found across Europe and temperate Asia, it's one of few butterflies that regularly hibernates inside buildings, barns, and hollow trees through winter.

Despite months of hibernation, adults can live up to 11 months — a remarkable lifespan for a butterfly. Early spring sightings are often overwintered adults rousing from their long sleep, wings looking surprisingly fresh.