Level 1 - Absolute Beginner
A butterfly has pretty wings. A new study says the wings can also trick birds.
The wings have stripes. When the butterfly flaps, the stripes seem to move down. But the butterfly is really going up.
A bird sees the wrong direction. It is harder to catch the butterfly.
Scientists filmed butterflies very slowly. They also asked 100 people to catch fake butterflies on a screen.
- butterfly
- An insect with big, colorful wings.
- wing
- The part of a bird or insect used to fly.
- stripe
- A long line of color.
- trick
- To make someone believe something wrong.
- bird
- An animal with feathers that can fly.
- catch
- To get something that is moving.
- study
- A careful test to learn something new.
- slowly
- Not fast.
Level 2 - Elementary
A study published in the journal Nature suggests that butterfly wing patterns can fool hunting birds. The work was led by Jolyon Troscianko of the University of Exeter.
When a butterfly flaps its wings down, the stripes on the front wings seem to slide downward. When the wings go up, the stripes fold and twist, so the upward motion is hard to see.
The result is a false signal. A bird may think the butterfly is moving down when it is really flying up.
The team used slow motion video of real butterflies, computer models and a touchscreen game. In the game, 100 volunteers acted as birds and tried to catch virtual butterflies.
- journal
- A magazine that publishes science studies.
- pattern
- A repeated design of lines or shapes.
- fool
- To trick someone.
- slide
- To move smoothly across a surface.
- signal
- A sign that gives information.
- virtual
- Made by a computer, not real.
- volunteer
- A person who helps without being paid.
- model
- A computer or object used to test an idea.
Level 3 - Intermediate
A study in the journal Nature reports that the patterns on butterfly wings can create motion illusions that make it harder for birds to judge how fast a butterfly is flying and in which direction. The research was led by Jolyon Troscianko, a professor at the University of Exeter.
Troscianko said that the first slow motion video he ran through a bird vision model seemed to show downward motion even though the butterfly was rising. On the downstroke, stripes on the forewings appear to slide down. On the upstroke, the wing folds and twists in line with the flight direction, so the downward motion looks stronger overall.
The team combined high speed filming of real butterflies, computer modelling, simulated evolution and touchscreen experiments. In the experiments, 100 volunteers acted as predators and tried to catch virtual butterflies.
The idea that bold stripes can confuse hunters is called motion dazzle. Earlier tests with zebras, snakes and lizards gave mixed results, partly because many studies ignored how wings and limbs move. When the team compared their patterns with about 400 European species, they found that the illusion is widespread.
- illusion
- Something that looks different from what it really is.
- forewing
- One of the two front wings of an insect.
- upstroke
- The upward movement of a wing.
- predator
- An animal that hunts other animals.
- simulated
- Imitated using a computer or model.
- evolution
- Slow change in living things over many generations.
- widespread
- Found in many places or cases.
- mixed
- Not clearly one result or the other.
Level 4 - Advanced
A study in Nature reports that the markings on butterfly wings can interact with the beat of those wings to generate motion illusions, making it harder for birds to judge a butterfly's speed and heading. The research was led by Jolyon Troscianko, a professor at the University of Exeter.
Troscianko recalled that the first slow motion clip he fed into a bird vision model seemed to glow with downward motion even though the insect was climbing. On the downstroke, stripes on the forewings appear to slide earthward; on the upstroke the wing furls and twists into line with the direction of travel, so the downward signal ends up dominating.
To test the idea, the team triangulated between high speed footage of living butterflies, computer modelling, simulated evolution and touchscreen trials in which 100 volunteers played the part of avian predators chasing virtual prey.
The notion that bold stripes bewilder hunters, known as motion dazzle, has long been debated; experiments on zebras, snakes and lizards have yielded equivocal evidence, partly because many ignored the movement of wings and limbs. Comparing their patterns with roughly 400 European species, the researchers concluded that the illusion is far from rare.
- interact
- To affect each other.
- heading
- The direction in which something is moving.
- furls
- Folds up tightly.
- triangulated
- Cross-checked using several independent sources.
- avian
- Relating to birds.
- bewilder
- To confuse deeply.
- equivocal
- Open to more than one interpretation.
- dominating
- Having the strongest effect.
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