What is the powder like material found on the wings of butterflies? What is its use?

Butterflies and moths belong to the taxonomic order, Lepidoptera. In Greek, Lepido means scales and Ptera means wings. In other words, Lepidoptera means scaly wings.

As the order name implies, the powder like materials found on the Butterfly wings are called scales.

Butterfly wings have two membranous layers which are made up of chitinous materials.

Wings are nourished by a number of tubular veins which play a significant role in oxygen exchange.

Like all other insects, butterflies also have two pairs of wings, viz forewings and hind wings. The wing surfaces are generally covered with unicellular, setae(hair) like or flattened, overlapping scales.

Scales are outgrowths of the body wall and they are of different colours.
There are two fundamental mechanisms by which colous are produced on butterfly wings. the ordinary colour, the first one, is due to the presence of chemical pigments, which absorb certain wavelengths of the light and transmit or reflect others.

The second colour, which is known as iridescent colour, is produced by the interference of light due to multiple reflections within the physical structure of a material and thus most of the butterflies exhibit brilliant iridescence on their wings.