The Senses of Butterflies: Vision

Compound Eyes: Butterfly eyes are composed of thousands of image forming tiny eyes called ommatidia. Each ommatidium is a sensory structure with a lens, cones and retina cells. The ommatidia are arranged in the compound eye so that each individual eye is set at a slightly different angle from the next. This arrangement allows the butterfly eye to simultaneously see in all directions at the same time with a mosaic of individual images that form a whole picture. This type of vision is known as Omni-vision.

Seeing in Color: Cones in the butterfly ommatidia perceive color with different types of color receptors that form Tetrachromatic vision. Tetrachromancy involves four types of higher-intensity light receptors that allow the eye of a butterfly (or birds, some fish, some reptiles and very rare humans) to see a larger spectrum of colors than the normal human eye.

Humans have trichromatic vision. Our eyes perceive a different and smaller set of colors than those of the butterfly. Butterflies can see in many of the colors that we can, but they can also see higher frequency colors beyond violet. To get an idea of how a butterfly sees, take a look at the photography of Dr. Klaus Schmitt of Germany which shows how the same field of flowers is seen by the human eye, the butterfly eye and the eye of a bee.

Different species of butterflies may see different colors. Some species are red-green colorblind while other species have evolved to differentiate between reds and greens. Differences in the ability to perceive various colors likely impact how each species sees and interacts with their environment. One butterfly may have an easy time seeing a particular colored flower while another species may not.

Ultra Violet on the Wing: In 2010, researchers from UC Irvine released information that some butterfly species have specially developed photoreceptors in their eyes for detecting UV colors and that these same species also express a UV-yellow pigment on their wings. Invisible to the human eye, this pigment may help butterflies detect appropriate mates so they have more time to eat, rest, lay eggs and thrive. Species that look very similar to us likely look very different to butterflies who can use the UV markings to quickly determine if another butterfly is of their same species or not.

The Big Picture: Hollywood movies often depict butterfly or insect vision as dozens of copies of a single image, like what you might see through a kaleidoscope. Right before its demise, a movie fly is often depicted as seeing dozens of images of the same flyswatter coming in for the kill. Let’s take a look at how an insect with compound eyes really sees.

Each ommatidium of insects with compound eyes sends a signal to the insect’s brain at the same time and the effect is like that of a mosaic. The picture is quite a bit like an overly pixilated image would appear to human eyes. The vision of butterflies allows these insects to see colors and the rough shape of things but not the fine details that the human eye can distinguish. Each ommatidium sees a part of the whole, but unlike human eyes, these tiny individual eyes are unable to focus.

Take a look at the photograph above which shows a selection of flowers from the gardens. In the photograph to the left you see blurred images much like the type of vision a butterfly might perceive.

Butterflies can see in amazing color and their eyes reveal a nearly 360 degree views of the world around them, even if the picture isn’t entirely clear. They are able to look at the flower they are probing with their proboscis, a butterfly flying to their right and the approaching predator behind them at the same time.