Butterflies and moths are both insects of the order Lepidoptera , which encompasses about 125,000-150,000 species worldwide. If you rub the scales off, the wings become transparent and membranous, like those of a fly. They'll brush a plant with their feet as they fly by to see if it's the right one for depositing their eggs. A butterfly's eyes are built something like bifocals. They have vision all around, but the area in front and below is magnified to help them find the right plant sources.
Butterflies can see colors in the ultraviolet range.