Butterfly Symmetry: Mirror Wings, Scale Colors, and How to Color Them

Fold a picture of a butterfly down the middle and the two halves nearly match: the same spots, the same bands, the same colors. That mirror quality is what makes the butterfly theme on daubday so pleasant to color. This guide covers where the symmetry comes from, how wings make color, what eyespots may do, butterflies in Korean painting, and how daubday's pictures are built.

Two halves of one pattern

Like most animals, butterflies are bilaterally symmetric: an imaginary line down the middle of the body divides them into left and right halves that are close mirror images. A butterfly has four wings, a pair of forewings in front and a pair of hindwings behind. The pattern on the left forewing mirrors the right forewing, while the forewing and hindwing on the same side usually look quite different.

The left and right wings develop separately but follow the same developmental instructions, so the same pattern forms on each side in reverse. The match is close, not perfect. A real butterfly may have one spot slightly larger than its twin, patches where scales have rubbed off, or a ragged edge left by a bird. The upper and under sides can also differ completely.

Color made of scales

The scientific name for butterflies and moths, Lepidoptera, comes from Greek words for scale and wing. Their wings are covered in tiny scales, each grown from a single cell, overlapping like roof tiles. The powder left on your fingers if you touch a butterfly is made of these scales.

Scales produce color in two very different ways:

• Pigment. Some scales contain chemicals that absorb certain colors of light. Melanins give blacks and browns, and other pigments give many yellows and whites.
• Structure. Other scales carry microscopic ridges and layers that reflect light so that some colors are strengthened and others cancel out. Many blues, greens, and shimmering colors come from structure, not pigment.

The morpho butterflies of Central and South America are the classic example. Their brilliant blue is not a blue pigment: layered structures on the scales reflect light again and again, and the color shifts as your viewing angle changes. The undersides of the wings are brown with eyespots, so a morpho flapping through a forest seems to flash blue on and off.

Eyespots and what they may do

Many butterflies carry eyespots, round markings built from rings of contrasting color, often with a bright point in the middle. In the developing wing, each one forms around a small organizing center called a focus.

Biologists have proposed several jobs for eyespots, and the answer probably differs between species:

• Startling predators. A large pair of eyespots suddenly revealed may make a bird hesitate long enough for the butterfly to escape.
• Deflecting attacks. Small eyespots near the wing edge may draw a peck away from the body. A butterfly can often survive a torn wing; an injured body is far more serious.
• Finding mates. In some species, eyespots appear to play a part in courtship and mate choice.

Whether eyespots work by imitating the eyes of larger animals is still debated.

Butterflies in Korean painting

In Korea, flowers and butterflies were often a metaphor for love between a man and a woman, and paintings of the two together, called hwajeopdo, were very popular. In folk painting, flowers and butterflies expressed hopes for love and harmony between married couples, which made them a natural choice for decorating a home.

The best-known butterfly painter of the late Joseon period is Nam Gye-u, a nineteenth-century artist so devoted to butterflies and flowers that he was nicknamed Butterfly Nam. His butterflies are known for their careful, lifelike detail.

How daubday's butterfly pictures are built

Every picture in the theme is generated from a seed and shows one butterfly centered left to right. Unlike some themes, these pictures are never flipped.

• Wings. The upper wings are either rounded or pointed, sweeping up and out, and each picture uses one of the two shapes. The lower wings are always rounded.
• Spots. Each upper wing has an oval patch with a small round dot in it. Each lower wing has a round spot, usually with a smaller dot at its center, a simple eyespot. Some butterflies also have a small oval near the body on the upper wing.
• Body. A slim body and round head run down the middle, with two curved antennae ending in small knobs, like the clubbed antennae that set most butterflies apart from moths.
• Background. One of several designs, from plain to checked, plus a few scattered dots. The background is not mirrored.

The butterfly is drawn the same way at every difficulty. More detailed pictures add background dots or bands and keep more small slivers as separate areas.

Coloring tips

1. Work in mirrored pairs. Matching wings and spots share numbers, so after filling a piece on one side, fill its twin on the other.
2. Use the shared spot colors. The large spots on the upper and lower wings share one number, and the small dots inside them share another. Select one and visit all four wings.
3. Check the spot near the body. The small oval near the body on the upper wings does not always come in a pair. Some pictures have it on both sides, some on neither, and some on only one, so read the numbers there instead of assuming.
4. Zoom for the centers. The dots in the middle of the spots are among the tiniest areas. Zoom in, or tap Hint to jump to the largest unfilled area of your color. The guide on small areas has more tricks.
5. Treat the background separately. It is not mirrored, so the pairing trick does not help there. Fill its large pieces, then tap Fit to compare both wings and catch anything you missed.

If you like the calm of symmetric designs, the mandala guide covers coloring rings of repeating shapes, and color basics explains why some color pairs look especially vivid side by side.