Why moths rather than butterflies became the motif of dark decor

Butterflies are the ones on the greetings cards. Moths are the ones on the black jewellery. Both are Lepidoptera, both have four scaled wings, and the boundary between them is much blurrier than the gift shop suggests. The reasons the moth ended up carrying the darker half of the aesthetic are partly biological, partly historical and partly just a matter of what shape and colour a small object needs to be.

There are far more moths, and butterflies are a kind of moth

Something in the region of 160,000 species of Lepidoptera have been described. Fewer than 20,000 of those are butterflies. The ratio is roughly eight or nine moths for every butterfly, and since most of the world's moths are small, brown and poorly studied, the true ratio is probably worse than that.

More awkwardly for the categories, butterflies are not a separate thing from moths. They form one branch within the moths, which means that in strict terms a butterfly is a moth that flies in the daytime and has good public relations. Moth is not a scientific group at all. It is everything in the order that is not a butterfly.

How to tell them apart, and why the rules leak

The most reliable field rule is the antennae. Butterfly antennae end in a small club or knob. Moth antennae are either plain and tapering or elaborately feathered, and almost never clubbed. If you only remember one test, remember that one.

The others all leak. Butterflies usually hold their wings up over the back at rest and moths usually hold theirs flat or swept back, but there are exceptions in both directions. Butterflies fly by day, except that plenty of moths do too: burnet moths, hummingbird hawkmoths and clearwings are all day-flying and several are brightly coloured. Butterflies are colourful and moths are drab, except that the most spectacular Lepidoptera on earth include moths and the drabbest include butterflies.

The technical distinctions are less satisfying and more dependable. They involve the way the fore and hind wings are coupled together in flight, and the structure of the antennal base. Neither helps you from across a garden.

The lamp, and the thing everyone gets wrong about it

The single strongest association moths carry is with artificial light, and the tidy explanation most people have heard, that moths navigate by the moon and a bulb confuses them into a spiral, does not hold up well. It struggles to explain why insects circle a light at close range rather than flying into it, and it struggles with the geometry.

Recent work points instead at the dorsal light response: flying insects keep their backs towards the brightest part of the sky to stay the right way up, and near a bright lamp that reflex tips them into orbiting it. Call it the current best explanation rather than a settled one. What matters for the motif is only that the association is real: moths do come to lights, which is why people meet them indoors at night, and why the moth is the insect of lit windows and porch lamps.

Moths are the right colour

Most moths are built out of greys, browns, charcoals and dull creams, in matte scales, on a body that is often visibly furred. That is a palette, and it is a palette that sits quietly next to iron, oxidised silver and brass.

Butterfly colour is largely structural, produced by the microstructure of the scales rather than by pigment, which is why it flashes and shifts and photographs so well. That is precisely the problem for ornament: an iridescent blue competes with everything in a room and dates fast. A brown moth does not compete with anything.

Many moths also hide their colour. The underwing moths are mottled bark on the forewing and sudden orange or crimson underneath, visible only in flight. That is a better structural idea than straightforward prettiness, and it is why the resting pose is the one worth copying.

The shapes are better for making things from

A butterfly outline reduces to two circles on a stick. Shrink it to pendant size and it turns into a bow. Moth outlines hold up much better: the hawkmoths resolve into a narrow swept delta, the saturniids into a broad quartered square, and the geometers into a wide shallow triangle with a scalloped edge.

Scalloped and notched wing margins are the useful detail. They give a cast or cut edge something to do, so the silhouette still reads at twenty millimetres. That is why a cast moth ring keeps its shape across the finger where a cast butterfly would blur into an outline.

Antennae are the other gift. Feathered antennae give a maker two symmetrical fronds to work with, which is useful on anything that needs to look designed rather than traced. The cost is accuracy: the big plumes belong to silk moths and emperor moths, and sticking them on a hawkmoth is the most common error in moth jewellery.

The clothes moth, which is why some people flinch

Two species do nearly all the domestic damage in Europe and North America: the common clothes moth, Tineola bisselliella, and the case-bearing clothes moth. Both are small, drab and under 15mm across, and neither is anything like the moths people put on jewellery.

The adults do not eat your jumpers. They barely feed at all. The damage is done by the larvae, which digest keratin, so they eat wool, silk, feathers, fur and felt, and they prefer material that is dirty, undisturbed and dark. Synthetics are generally safe except where a blend gives them something to chew.

The practical controls are unglamorous. Wash or dry clean before storing, because sweat and food residue is what attracts them. Keep stored wool in sealed bags rather than open drawers. Vacuum the back corners of wardrobes, where the larvae live rather than fly. Freezing an infested item for a couple of weeks kills the larvae, and it is the only home remedy that reliably does. A natural fibre throw such as a flannel blanket is worth knowing the fibre content of for exactly this reason: cotton flannel is not on the menu, wool is.

How the motif acquired its meaning

Victorian collecting put moths under glass in enormous numbers, which gave the shape a formal, specimen-like presentation that persists: the spread wings, the pin, the printed label. Most moth ornament is still copying a dead insect in a case rather than a living one on a wall.

The figure of speech did the rest. Drawn to it like a moth to a flame is attested long before anybody understood why moths come to lights, and it put the insect permanently on the side of attraction to something harmful. None of that is in the animal. It is a brown insect with an orientation reflex.

Which is the useful way to think about any of these motifs. The moth is not more melancholy than the butterfly. It is matte, it is grey, it is symmetrical, it comes in good shapes, and it turned up in the house at night when somebody was already awake. A piece like a moth cut from iron inherits all of that, and none of it is a claim about anything except the shape on the wall.

The same logic applies well outside the Lepidoptera. A cast stag beetle earns its place for identical reasons: hard symmetry, an outline that survives being small, and a colour that does not argue with the room.

Questions people actually ask

What is the difference between a moth and a butterfly?

The most reliable difference is the antennae: butterflies have clubbed tips, moths have plain or feathered ones. Rules about day flight, colour and resting posture all have many exceptions.

Are there more moths than butterflies?

Many more. Of roughly 160,000 described Lepidoptera, fewer than 20,000 are butterflies. Butterflies are also, technically, one branch within the moths rather than a separate group.

Do moths actually eat clothes?

The adults do not. The larvae of two small clothes moth species eat keratin, so they damage wool, silk, fur and feathers. They prefer soiled, undisturbed fabric stored in the dark.