Butterfly Wing Structure and Function

Most people are familiar with many kinds of butterfly, The wings of butterflies are often their most distinguishing feature and come in many different shapes, colors, textures, and patterns. But, do you know how a butterfly wing works, or what it is made out of? 

Siproeta stelenes
Butterfly wings come in all kinds of colors. Credit: Pixnio CC0 1.0

Butterfly wings do more than just facilitate flight. Their patterns and colors can serve as a form of camouflage or mimicry, and the fine scales on the wings keep the insect insulated during the cold months. The special shape of the wings and scales gives butterflies their characteristic lofty flight patterns and surprising aerial maneuverability. Butterfly wings also act as a kind of heat sink which the insects uses to catch light and warm its body. 

Butterfly Wing Anatomy

Butterfly wings are composed mainly of thin layers of a protein called chitin, the same protein in the exoskeletons and hard shells of insects and arthropods. Each of the two wings is divided into two parts, the upper forewing and the lower hindwing. On both sides of the wings are overlapping layers of tiny scales also made of chitin. The scales are responsible for much of the wings’ interesting properties: their color, iridescence, and air flow around the wing. 

monarch butterfly wing
A close-up of the scales on the wing of a monarch butterfly. Credit: W. Warby via Flickr CC BY 2.0

Scales often contain pigments, substances that reflect a particular wavelengths of light. The concentration of the pigments is responsible for the oranges, browns, and blacks, and whites seen in butterfly wings. Greens, blue, and reds are often not created by pigments, but by the scattering of light by the microscopic structure of the scale itself. The tiny scales have microscopic ridges that scatter incoming light, creating the shiny colors and iridescence associated with butterfly wings. 

Functions of Butterfly Wings

Butterfly wings perform numerous functions. Most apparent, their colors and patterning can serve as camouflage, a warning sign, or as a form of mimicry. Butterflies can use their wings to blend into the background foliage to avoid predators, and the bright colors of wings can disorient or signal that the insect is unpalatable. In some cases, butterflies evolve to mimic the wing color and patterns of harmful species, tricking predators into leaving them alone. 

Functions of Butterfly Wings

Another function of butterfly wings is to trap heat and insulate the insect. The tiny scales on the wings absorb heat from the light, which regulates the insect’s body temperature. Even a tiny difference in scale thickness can drastically effect how well they absorb heat.  In this sense, butterfly scales can be seen as analogous to mammalian hair. 

Owl Butterflies hanging

Butterfly wing scales also aid in survival. The scales are designed to come off easily, so if the butterfly gets tangled up with a predator, they can slip away. Wing scales drastically reduce the amount of butterfly deaths from spider webs. The scales rub off on the sticky web, allowing the insect to free itself much easier. By the same token, touching a butterfly’s wings can rub its scales off, which can negatively affect wing functioning. For that reason, it is always best to not handle butterflies by their wings.