The common blue is a small blue butterfly with a wingspan of up to 3.6 cm. Males are very consistent in appearance. The upper wings are vibrant blue with plain white fringes (see today’s photograph).
Interestingly, there is no blue pigment creating this shade. The blue coloration is entirely evoked by an optical effect.
The upper sides of the butterfly wings are covered in microscopic, specially shaped scales. These bend and reflect light waves. When light hits the ridges of the scales, most light wavelengths cancel each other out, but blue wavelengths reinforce each other and reflect back brightly.