A butterfly on a flower and a close-up of the cells that make up its eye

COMPOUND EYE: The eyes of butterflies and other insects are made up of repeating units that each contain their own light-detecting cells.

COURTESY OF ZACHARY MACDONALD (BUTTERFLY); MARTIN OEGGERLI/SPL/SCIENCE SOURCE (EYE)

STANDARDS

NGSS: Core Idea: LS1.D, LS4.C

CCSS: Literacy in Science: 7

TEKS: 6.2A, 7.2A, 8.2A, B.2E

Butterfly Vision

An experiment sheds light on how butterflies find their way

January 20, 2020

By Jacqueline Adams

AS YOU READ, THINK ABOUT how animals use their senses to navigate.

COURTESY OF ZACHARY MACDONALD

Butterflies bob and weave as they flutter through the air, going one way and then, all of a sudden, another. To a person, this flight can appear aimless. But butterflies really are trying to get somewhere: They’re searching for the ideal habitat to live, feed, and reproduce.

How, exactly, do seemingly bumbling butterflies navigate? That’s what Zachary MacDonald, a biology graduate student at the University of Alberta in Canada, wanted to find out. Other species don’t always perceive the world the way humans do. He knew it would be a challenge to determine whether butterflies rely on vision or other senses—like smell—to find a suitable home. Luckily, MacDonald had a flash of inspiration about how to investigate the mystery.

One day, MacDonald was taking close-up photos of butterflies he was studying. He wondered if the camera’s flash was blinding them. If you’ve ever had a bright light flashed in your eyes, you may have seen spots afterward that made it hard to see. This temporary loss of vision is called flash blindness. It occurs when light overwhelms the light-detecting photoreceptor cells in your eyes. MacDonald thought he might be able to use the same phenomenon to learn whether butterflies depend on their eyes to find their way.

Butterflies bob and weave through the air. They flutter one way, and then they suddenly go another way. This flight can appear aimless to a person. But butterflies really are trying to get somewhere. They’re searching for the right habitat to live, feed, and reproduce.

How do the fluttering butterflies find their way around? Zachary MacDonald wanted to find out. He’s a biology graduate student at the University of Alberta in Canada. Other species don’t always experience the world the way humans do. Do butterflies use vision or other senses, like smell, to find a good home? MacDonald knew it would be a challenge to learn the answer. Luckily, he had a flash of inspiration about how to investigate the mystery.

MacDonald was already studying butterflies. One day, he was taking close-up photos of them. He wondered if the camera’s flash was blinding them. If a bright light flashes in your eyes, you may see spots afterward. For a while, it’s hard to see. This temporary loss of vision is called flash blindness. It occurs when light floods the photoreceptor cells that detect light in your eyes. MacDonald thought he could use flash blindness to learn if butterflies depend on their eyes to find their way.

INSECTS ON THE MOVE

The graph below shows the percentage of butterflies that reached a nearby island after being exposed to camera flashes compared with butterflies that weren’t exposed. Did distance from the island affect the butterflies’ success?

INSECTS ON THE MOVE

CATCH AND RELEASE

For his experiment, MacDonald used nets to catch dozens of wild Speyeria cybele and Speyeria atlantis butterflies. He placed them in a dark cooler to keep them calm. Then he boarded a boat and took the cooler to a spot in a nearby lake where only one island was visible.

For half of the butterflies, MacDonald triggered intense camera flashes above, below, in front of, behind, and on both sides of their eyes. Insects’ compound eyes consist of thousands of units called ommatidia. “They face in almost all directions,” says MacDonald. “So, we wanted to make sure that we exposed all of them to the flash.” Then he released all the butterflies— those that had been exposed to camera flashes and those that hadn’t—one by one.

MacDonald caught dozens of wild Speyeriacybele and Speyeriaatlantis butterflies in nets for his experiment. He placed them in a dark cooler to keep them calm. Then he got on a boat and took the cooler out onto a nearby lake. Only one island could be seen from this spot.

MacDonald set off strong camera flashes for half of the butterflies. He flashed above, below, in front of, behind, and on both sides of their eyes. Insects have compound eyes. They’re made of thousands of units called ommatidia. “They face in almost all directions,” says MacDonald. “So, we wanted to make sure that we exposed all of them to the flash.” The other half of the butterflies weren’t exposed to camera flashes. Then he released all the butterflies, one by one.

LAND AHOY!

Most of the butterflies that hadn’t been exposed to flashes soon spotted the island. “You could tell when they found it, because they just flew directly to it,” says MacDonald. But the flashed butterflies fluttered around randomly. The few that did find the island seemed to do so by chance.

MacDonald repeated the experiment farther from the island with similar results. The butterflies were navigating mainly by sight. We can never know exactly what it’s like to be a butterfly, says MacDonald, but science can provide clues to how these organisms experience the world.

The butterflies that hadn’t been flashed took off. Soon, most of them spotted the island. “You could tell when they found it, because they just flew directly to it,” says MacDonald. But the flashed butterflies fluttered around aimlessly. A few found the island, but they seemed to find it by chance.

MacDonald repeated the experiment farther from the island, and he got similar results. The butterflies were finding their way mainly by sight. We can never know exactly what it’s like to be a butterfly, says MacDonald. But science can provide clues to how these creatures experience the world.

INVESTIGATE IT!

Scientists often find clever ways to answer tricky research questions. They use these ideas to design experiments and gather data that can help them come to conclusions. Think about the challenges Zachary MacDonald faced during his investigation. Then answer the questions below.

What inspired MacDonald to use flashes from a camera to test the role of vision in butterfly navigation?

Why was it important to test butterflies using a method that would affect their sight but not their other senses?

Why do you think MacDonald didn’t attempt to blind the butterflies with a single flash from one direction?

How did MacDonald’s results indicate that butterflies relied mainly on vision to find suitable habitat?

INVESTIGATE IT!

What inspired MacDonald to use flashes from a camera to test the role of vision in butterfly navigation?

Why was it important to test butterflies using a method that would affect their sight but not their other senses?

Why do you think MacDonald didn’t attempt to blind the butterflies with a single flash from one direction?

How did MacDonald’s results indicate that butterflies relied mainly on vision to find suitable habitat?

Continue the Learning Journey

Think about how you use your senses to navigate the world. Then imagine a place you know very well, like your home, your school, or your favorite park. Describe that place using as many sensory details as possible. Think about what that place looks, smells, and sounds like. When you're done, consider how animals use their senses in different ways. Pick an animal that you know about, and describe that same place from that animal's perspective. Consider how they use their senses to navigate. How are the descriptions you wrote similar or different?

Butterflies have what are called compound eyes. You can make a model of a compound eye at home by using straws or paper. If you have straws, take 6 and cut them in half. Bundle them together. Then, hold the straws upright and wrap a long piece of tape all the way around them. If you don't have straws, you can use paper instead! Rip or cut a piece of paper to the size of an index card. Wrap the paper tightly around a pencil or pen, and secure it with tape or your finger. Then, slide out the pencil. You've made your compound eye! Look around your room until you find an object that's interesting to look at. Draw what you see in your notebook. Next, look at the same object through your model compound eye. Draw what you see. How do your two drawings compare?

Continue the Learning Journey

Think about how you use your senses to navigate the world. Then imagine a place you know very well, like your home, your school, or your favorite park. Describe that place using as many sensory details as possible. Think about what that place looks, smells, and sounds like. When you're done, consider how animals use their senses in different ways. Pick an animal that you know about, and describe that same place from that animal's perspective. Consider how they use their senses to navigate. How are the descriptions you wrote similar or different?

Butterflies have what are called compound eyes. You can make a model of a compound eye at home by using straws or paper. If you have straws, take 6 and cut them in half. Bundle them together. Then, hold the straws upright and wrap a long piece of tape all the way around them. If you don't have straws, you can use paper instead! Rip or cut a piece of paper to the size of an index card. Wrap the paper tightly around a pencil or pen, and secure it with tape or your finger. Then, slide out the pencil. You've made your compound eye! Look around your room until you find an object that's interesting to look at. Draw what you see in your notebook. Next, look at the same object through your model compound eye. Draw what you see. How do your two drawings compare?

Biology

Adaptations

Butterfly Vision

An experiment sheds light on how butterflies find their way

AS YOU READ, THINK ABOUT how animals use their senses to navigate.

INSECTS ON THE MOVE

INSECTS ON THE MOVE

CATCH AND RELEASE

LAND AHOY!

INVESTIGATE IT!

INVESTIGATE IT!

Continue the Learning Journey

Continue the Learning Journey

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