Okay, so they aren't really eyes. But they make you think twice about what you're seeing, don't they? If you were a bird, you might think you were dealing with a snake instead of a fat and tasty insect. Since some snakes eat birds, you might think twice about attacking and fly off in search of less threatening prey.
Spicebush Swallowtail Caterpillar, Papilio troilus
When it feels threatened, this caterpillar tucks its head under making it look more like a snake than a caterpillar.
Here's the same caterpillar in a more relaxed position instead of its scary snake mode.
Io Moth, Automeris io
We cheated a little on this one. Io moths tend to sit with their wings closed so you don't see the "eyes" until the moth flashes them, making it difficult to get a picture. This was a very fresh moth so Mr. Swamp was able to push the forewings open ever-so gently, allowing me to snap a photo of the hindwings.
Eyed Click Beetle, Alaus oculatus
Had I touched this beetle, or if it had seen me coming, it would have pulled its legs in and tucked its antennae away making it look even more "dangerous" to a potential predator. Had I picked it up and placed it on its back it would have flexed its body with a loud click and launched itself a couple of inches into the air in order to right itself.