Butterflies: the science behind the colour

Butterflies and moths are masters of disguise, able to appear as if they were the face of an animal, a rolled-up leaf or even a snake. Welcome to the colourful world of butterfly wings.

Silver-studded blue butterflies by Steve Brooks, entomologistThe Natural History Museum

Finding family
Each butterfly and moth species has developed a strategy to make the most of their biggest asset and defining feature: their scaly wings.

Butterflies and moths rely on colour in every aspect of their lives: sparring, courting, mating and hiding.

Golden helicon butterflyThe Natural History Museum

Butterflies can see more of the visible light spectrum than humans can. They can see a little further into the red end of the scale, and also further to the violet end, into ultraviolet light. This colour sensitivity helps them find flowers, camouflage into backgrounds and seek other butterflies.

Yellow-edged giant owl butterflyThe Natural History Museum

Evading predators

Some species have developed large eyespots on their wings. This tricks predators into thinking they have come face to face with a much larger creature.

The yellow-ringed eyespots on the wings of an owl butterfly (Caligo) look like the eyes of a feathery owl.

Lime butterflyThe Natural History Museum

A stark warning

Another way butterflies and moths protect themselves is by showing off their bright colours as a warning to predators.

The caterpillars of tiger moths (Arctia caja) and milkweed butterflies (Danainae) eat plants full of poisons, which they store. It makes them taste disgusting to the birds that eat them. Bright, bold colours such as reds and oranges in the adult moths and butterflies warn birds to stay away next time.

Other butterflies are not harmful if eaten, but they copy the colours of those that are in an effort to keep predators away. Female African mocker swallowtails (Papilio dardanus) can mimic the wings of up to five different and more poisonous butterfly species.

Dead leaf butterflyThe Natural History Museum

Blending in

The upper side of the wings of the Indian leaf butterfly (Kallima paralekta) are steel blue with an orange band.

However, the underside is a dull brown with lines that look like the veins of a leaf. When the butterfly stays still with the underside of its wings showing, it can appear just like a dead leaf and is nearly impossible to spot when nestled among foliage.

Squinting Bush-brown, Bicyclus anynana (2016) by Natural History MuseumThe Natural History Museum

Changing seasons

It usually takes millions of years for the colours we see on most butterflies to evolve. But some species are able to change colour within a generation or two.

The African squinting bush brown butterfly (Bicyclus anynana) has very small eyespots on its wings during the cool dry season of the South African savannahs. It hides from predators and is not very active. It does not live long, so several generations of the bush brown butterfly are produced in one year.

With the start of the heat and the rain of the wet season, the eyespots of the next generation of butterflies become much bigger as they become more active to feed and mate. The air temperature and humidity surrounding the developing caterpillars determine what colour pattern the next season's adults will have.

Credits: Story

For more information and to book tickets to the exhibition, visit the Museum's website.

Credits: All media
The story featured may in some cases have been created by an independent third party and may not always represent the views of the institutions, listed below, who have supplied the content.
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