July, August, and September are the months of insects in southeastern Pennsylvania. And many kinds of insects have unique ways to protect themselves, including exhibiting large, fake eyes that frighten away would-be predators.

Several kinds of insects in woods and suburbs of the eastern United States — including io moths, spicebush swallowtail butterfly caterpillars, and eyed click beetles — display dark spots in strategic places that resemble the eyes of larger creatures.

Those “eyes” formed by trial and error through many, many years. And only the insects that developed protective eye spots lived long enough to reproduce themselves, with the genetic code passed along to grow those “eyes,” as their ancestors did.

Io moths have a round, dark spot (the O) on each of two hind wings. Each dark O has a bit of white that resembles reflected light. And each O has a black semi-circle around it (the I).

Io moths keep their wings flat and closed when at rest by day on a tree limb or other object. But when alarmed, the moth abruptly opens its four wings, revealing the two dark spots on the hind wings and its abdomen.

Those “light-reflecting” black spots and the abdomen, suddenly seen together, should make a bird or other predator feel as though it is looking into the face of an owl, scaring that predator away.

Newly hatched spicebush swallowtail butterfly caterpillars are brown and white and look like bird droppings on the spicebush and sassafras leaves they consume. But as those larvae grow, they are mostly green, which camouflages them, and each one uses its silk to wrap a leaf around itself as it ingests that leaf from the inside.

But spicebush caterpillars’ best defenses are the two large black spots on their humped-up upper thoraxes, just behind their heads. Each “eye” has yellow “lids” and white spots in the black that looks like reflected light. There is even a yellow “ear” behind each “eye.”

Those fake eyes appear so real that when I look deeply into them, which I have, they appear to be staring back at me!

Eyed click beetles are about an inch long and black with many tiny white dots, which camouflage them on logs and among dead leaves on forest floors. Click beetles that find themselves vulnerable on their “backs” quickly flip upright by snapping muscles between their thoraxes and abdomens, often with an audible click.

Their wormlike larvae, called wireworms, are thin and segmented, living in rotting logs and ingesting beetle grubs they find in those logs.

And eyed click beetles have two large, oval black spots on their upper thoraxes that, again, resemble black eyes, but with white rims. I imagine those false eyes would startle away a skunk or bird that dug one out of a log or woodland soil.

These kinds of insects developed fake eyes to frighten away would-be predators, as well as developing camouflage and other means of defense. These are attractive and intriguing critters that are well worth knowing, as all wild plants and animals are, each species in its own way.


Clyde McMillan-Gamber is a retired Lancaster County Parks naturalist.

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