The beauty of butterfly wings

Butterfly wings are the most striking part of a butterfly’s body and are certainly the reason why butterflies are so popular with people and why they are so attractive. The combination of all sorts of colours on butterfly wings is not just a random freak of nature, but it has several purposes.

One of these is recognition between individuals of the same species. At mating time, the male attracts the female by the colour combination on its wings. Last but not least, the colours on the wings serve as protection against predators. For example, some dull-coloured moths perch on tree bark during the day and, thanks to their inconspicuous colouring, blend in perfectly with the ground and escape the eyes of predators. Other butterflies have a warning colouration. Our hero Apollo will display its red-meshed hindwings in an attempt to scare off predators.

But what makes butterfly wings so colourful? It may sound surprising, but the colour is caused by thousands and thousands very tiny formations, a few tenths of a millimetre in size, which are shaped like scales. Even the scientific name of Lepidoptera butterflies is derived from these scales. In fact, the word Lepidoptera is a compound of the two Greek words lepís (scale) and pterós (wings) and was first used by the father of scientific nomenclature for plants and animals, Carl Linné.

Eye with scales on the hindwing of the Apollo

The scales are coloured with various pigments and this is one of the reasons for the colourfulness of butterfly wings. In addition, in some butterflies, the edges and various surface structures of the scales refract and reflect light and this causes them to shine.

The scales are stacked side by side on the butterfly’s wing and overlap each other; they are arranged like shingles on a roof. In some butterflies the number of scales per square millimetre can be more than 500, but in Apollo the number of scales is smaller, giving the wings a translucent appearance. If you ever catch a butterfly in your hand and get “coloured dust” on your hand, it is these scales that you have wiped off the butterfly’s wing.

The edge of the wing of Apollo. The scales are not as densely packed here, so the wing margin has a translucent appearance

The scales are therefore responsible for the colour and lustre of the butterfly’s wings. But they also have other functions. They are filled with air, which makes them very light and helps butterflies fly. They also serve as excellent thermal insulation. Scientists believe that this is the main reason why butterflies evolved scales. This is because they are not only on the butterfly’s wings, but also on the butterfly’s chest and other parts of the butterfly’s body, helping to maintain the high body temperature needed during flight.

Enlarged scales that are arranged like shingles on a roof