Butterflies are insects. However, unlike most insects, butterflies have wings that remain free of dirt, and the hind legs carry pollen. Butterflies have scaly wings in place of the hairy wings of other insects. The scales of these wings come off when they rub against objects, leaving the wings clean.
How do butterflies clean their wings?
Butterflies’ wings are covered with tiny, overlapping scales. These scales look a bit like shingles on a roof and are aligned in the same direction. They are made of chitin, which is a strong biopolymer- the same material as human fingernails. But unlike human nails, butterfly scales are imbued with very special properties that help them to keep clean. Different attributes of the wings lead to it cleaning itself.
What is the function of these aligned, shingle-like microscopic scales?
First, they result in the anisotropic flow of water on the wings. When a solid or liquid possesses the same properties in all directions, it is isotropic. If the properties change when there is a change in direction, it is anisotropic. The aligned scales of a butterfly wing can orient the flow of water, and so it is an anisotropic flow.
The second feature of these aligned scales that helps cleanse the wing is that they actually minimize surface area and friction compared to an isotropic surface structure. For example, imagine walking through wet grass with tennis shoes that have treads (aligned grooves). The grass will be less likely to stick to your shoes than if you were wearing smooth-soled shoes (no grooves).
Butterflies have been known to have anisotropic (directionally dependent) properties. Fluid flow on the wings is influenced by the arrangement of the scales on them. The scales are aligned, shingle-like, and overlapping.
The overlapping scales can be observed when a butterfly’s wings are viewed under a microscope. When this happens, it looks like there are two sets of wings instead of one. These overlapping scales give the impression that there are two pairs of wings.
Butterfly wings are unique and interesting for several reasons. Their wings are different in many ways from the wings of other insects. Their wings and legs contain small hooks that make it easy to perch on plants easily. When butterflies land and leave their footprints, they come off easily. The scales on butterfly wings come off when they rub against an object because they are loosely connected.