Peacock butterfly

 A-level Biology: The Peacock butterfly (Aglais io) shows brilliant eyespots — a classic example of anti-predator adaptation. These eyespots mimic the eyes of larger animals to deter birds and other predators. Evolution in action on a Buddleia!  #ALevelBiology #Adaptations

The Peacock Butterfly – A Masterclass in Anti-Predator Adaptation

While strolling through the garden one sunny afternoon, I spotted a flash of crimson wings fluttering over the Buddleia. A closer look revealed the unmistakable Peacock butterfly (Aglais io), feeding lazily on the vivid pink blossoms. But this wasn’t just a pretty picture—it was a live demonstration of evolutionary biology in action.

A-Level Biology Spotlight: Adaptations and Natural Selection

In the A-level Biology syllabus, students are asked to understand how adaptations improve an organism’s chances of survival and reproduction. The Peacock butterfly is an ideal case study.

Its most striking feature? The large, bright eyespots on each wing. These aren’t just there for decoration—they’re part of a clever anti-predator adaptation.

What are Eyespots?

Eyespots are circular, eye-like markings found on the wings of some butterflies and moths. In the case of the Peacock butterfly, these spots are incredibly vivid, with concentric circles of black, blue, and yellow. When threatened, the butterfly flashes its wings open to reveal the eyespots in a startling display.

This behaviour serves several biological functions:

• Mimicry: The eyespots resemble the eyes of a much larger animal, potentially scaring off birds or small mammals.

• Startle Response: The sudden flash of bright colours can surprise a predator long enough for the butterfly to escape.

• Deflection: Predators may aim for the spots, which are located on the less vital parts of the wing, rather than the head or body.

These are great examples of behavioural and structural adaptations working in tandem to increase survival.

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Survival of the Fittest on the Wing

This links directly to Darwin’s theory of natural selection. The ancestors of the Peacock butterfly may have varied in their wing markings. Those with better-developed eyespots were more likely to survive bird attacks and reproduce—passing on their successful trait to the next generation.

Over many generations, this trait became more common in the population. What we now see is the result of evolution acting on a successful adaptation.

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A Note on Habitat and Food Sources

You’ll often find Peacock butterflies in gardens, woodland edges, and meadows. They particularly love Buddleia (sometimes called the "butterfly bush"), which provides rich nectar for adult butterflies in the summer months.

The caterpillars feed on stinging nettles, which gives them a natural defence early in life—few animals want to rummage around in a nettle patch!

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Final Thoughts for Students

Next time you’re revising for your A-level biology exam and hit the section on adaptations, think about the Peacock butterfly. You’ve likely seen one yourself—what better revision tool than a live example?

Key Terms to Remember:

• Adaptation – A feature that increases an organism’s chances of survival.

• Mimicry – An adaptation where one species evolves to resemble another.

• Natural Selection – The process where the fittest organisms are more likely to survive and pass on their genes.

• Behavioural Adaptation – An action or pattern of behaviour that aids survival.

• Structural Adaptation – A physical feature that increases the organism's chance of survival.

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Bonus Activity for Class or Home Study
Go outside and observe butterflies in your garden or local park. Photograph them if you can. Try to identify them and list any visible adaptations. Think about how each helps the butterfly survive.

Science isn’t always confined to the lab. Sometimes, it lands right on a Buddleia in your garden.