How Butterflies Use Fake Eyes to Fool Predators

Eyespots in Butterflies

Story at-a-glance -

  • Many species of fish, insects, frogs, and even pheasants have what are known as “eyespots”
  • Eyespots are conspicuous markings that resemble eyes, but which are often found on the creature’s wings, torso, or tail
  • The spots lure predators to non-essential body parts, confuse them about which direction the insect may be heading in, and even fool them into thinking their prey is another species entirely

By Dr. Becker

Many species of fish, insects, frogs and even pheasants have what are known as “eyespots” in areas other than their heads. As their name suggests, eyespots are conspicuous markings that resemble eyes, but which are often found on the animal’s wings, torso, or tail.

It might seem unusual at first, as multiple eyespots could theoretically attract a predator. In so doing, however, they encourage the predator to attack non-essential parts rather than the creature’s more vulnerable areas.

Eyespots can also be confusing, fooling a predator into thinking the insect’s head is at the other end of its body. This could cause the attacker to misjudge the insect’s next move and miss it entirely or at least spare its life.

Even more intriguing, one species of butterfly has eyespots that look differently depending on whether it’s the wet or dry season!

Resourceful Butterfly Has Different Eyespots Depending on Season

The Bycyclus anyana butterfly species multiplies rapidly, with five generations being born each year. Due to a genetic trick of sorts, the butterflies end up with two different eyespot patterns for the wet and dry seasons.

According to Discovery News:1

“In the wet season, the resourceful butterfly creates big, bright eyespots -- the better to fool typical predators of the moment, such as praying mantids, into attacking the bright spots on the wings instead of the head or body.

…The butterfly's wings are likely to be badly damaged in an attack, but the made-you-miss trick at least gives it a chance to escape and live to procreate another day.

In the dry season, meanwhile, the butterfly sports small, dull eyespots… Most insect predators are dead at this time, but birds are still a threat. The butterfly's drab appearance can help it avoid becoming a meal, because birds have a harder time detecting it.”

While it’s long been thought that some eyespots help to deflect attacks away from vulnerable body areas, a study published in Proceedings of the Royal Society B demonstrated that the eyespots really work.2

Praying mantids had an easier time detecting wet-season butterflies with larger, bright eyespots… but a harder time actually catching them compared to dry-season butterflies with small, dull eyespots.

According to the study:

“Mantids attacked the wing eyespots of WS [wet season] butterflies more frequently resulting in greater butterfly survival and reproductive success …Regardless of whether the butterfly was WS or DS [dry season], large marginal eyespots pasted on the hindwings increased butterfly survival…”

Other Species Use ‘Fake Eyes’ to Fool Predators Too

The Bycyclus anyana butterfly species is only one example of how fake eyes may help ward off predators. Certain caterpillars have large eyespots on the front of their bodies, which make them appear like larger snakes. A study by Dr. John Skelhorn at Newcastle University found that birds did, in fact, hesitate in attacking caterpillars with eyespots that seemed to mimic a snake’s head.3

One species of frog native to the savannah of Brazil has eyespots on its rear end, just above its hind legs. When a predator approaches, the frog puffs up its body and raises its rear to “stare” down the predator with its large “eyes.” The eyes also have a gland in the center that produces a toxin potent enough to kill 150 mice… offering yet another layer of protection.4

But eyespots aren’t always used for protection. Peacocks, for instance, use them to help attract a mate. In one study, when male peacocks had a significant number of the eyespots on their feathers covered up with black and white stickers, peahens showed little interest.5

Some Butterflies Even Mimic Snakes or Foxes to Survive

Eyespots are not the only trick that butterflies keep up their sleeves. Their wings contain eye-catching patterns of all forms, including those designed to act as camouflage or a veritable “costume” of sorts. One species of butterfly, for instance, has a pattern on its wings that looks like a snake’s head, and the butterfly will even writhe on the ground to further fool its predator.

Other butterflies have patterns made to resemble toads, the face of a fox or inedible beetles. Many butterflies may also sport camouflage to blend in with leaves, bark, or other parts of a plant. Professor Philip Howse, a retired entomologist from Southampton University, told the Telegraph:6

"We as humans are able to instantly recognize them as a butterfly because we see the whole insect. The eyesight of birds and other insectivores, however, is different and they tend to focus in on the details.

This means they will see eye spots or distinctive colors and associate them with other species. It allows butterflies and moths to use imperfect mimicry to great effect.

It doesn't matter that the butterfly might be smaller than the animal it is mimicking, as in that first crucial glance for the predator it will simply appear to be further away."

Butterflies Are in Danger from What Might Be the Worst Predator of All…

Humans. Monarch butterflies have a distinctive bright orange and black color pattern that serves as a warning to predators. Not only do they have an unappealing taste, but they’re poisonous when eaten. Unfortunately, this survival advantage does little to protect monarchs from man-made threats.

Due to the increased use of herbicides like Roundup on genetically modified crops, milkweed is disappearing. The monarch butterfly cannot survive without the ample presence of milkweed.

This perennial plant is the only plant on which the monarch will lay its eggs. Once the larvae hatch, the caterpillar eats the plant. Without milkweed along its migratory path, the monarch simply cannot reproduce.

The loss of milkweed, combined with other threats like logging at overwintering sites, extreme weather, diseases, parasites, and insecticides used in agricultural areas, and monarch populations have been facing a dramatic decline. An assessment completed by NatureServe and The Xerces Society for Invertebrate Conservation revealed, in fact, that North America’s monarch butterflies are vulnerable to extinction.7

If you want to help support monarchs and other butterflies, plant milkweed where you can and a butterfly garden, too (milkweed is poisonous, so keep it out of reach of children and pets.) Additional plants that will attract butterflies include the following:8

Coneflowers Impatiens Marigolds
Phlox Sunflowers Verbena
Asters Bee balm Butterfly weed
Chrysanthemums Daisies Purple coneflower
Sedum Yarrow New England aster
Bergamots Black-eyed Susan Butterfly flower
Coreopsis Purple ageratum  

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