Butterfly vs Moth: Antennae, Wings and Other Differences

Key differences at a glance

Butterflies and moths together make up the insect order Lepidoptera, meaning “scale wings”, with roughly 160,000 described species. Both have wings covered in tiny overlapping scales, a coiled feeding tube called a proboscis, and a life cycle of egg, caterpillar, pupa and adult.

Only about 19,000 of those species are butterflies. Everything else, roughly nine species in ten, is a moth. That is why no single feature separates the two groups perfectly. The rules below work most of the time, but each has exceptions, which are part of the fun.

A familiar pair shows the contrast well: the monarch butterfly, with its clubbed antennae and daytime flight, and the luna moth, with broad feathery antennae and a life spent flying at night.

Antennae: clubs versus feathers

Antennae are the most reliable clue. A butterfly’s antennae are long and slender with a thickened club at the tip. Skippers, a family of small, stout butterflies, often have a club that ends in a little hook.

Moth antennae come in more shapes. Many are thread-like and taper to a fine point. Others are feathery, with side branches that greatly increase their surface area. Feathery antennae are especially broad in the males of silk moths, such as the luna and polyphemus moths, which use them to smell the scent signals, or pheromones, released by females, sometimes from long distances.

There are exceptions. Burnet moths, common day-flying moths of European meadows, have antennae that thicken toward the tip, and the tropical sun moths have clubbed antennae much like a butterfly’s.

Wings: resting posture and the frenulum

Most butterflies rest with their wings closed and held upright over their backs, showing the underside. Many moths rest with their wings spread flat or folded like a tent over the body. Butterflies also open their wings to bask in the sun, and skippers often hold them half open, so posture alone can mislead.

A more technical difference lies in how the wings are linked in flight. Most moths have a frenulum, a stiff bristle or group of bristles on the front edge of the hindwing that hooks under a catch on the forewing, so the two wings beat as one. Butterflies have no frenulum; instead, an enlarged lobe at the base of the hindwing overlaps the forewing.

Again, nature breaks the rule. The male regent skipper of Australia is a butterfly with a frenulum, while many large moths, including the luna moth and other silk moths, lack one.

Day versus night

Butterflies are mostly active in daylight, when they rely on the sun’s warmth and use color vision to find flowers and mates. Most moths fly at dusk or at night and find their way largely by smell. Many are drawn to artificial lights, a puzzle explored in why are moths attracted to light?

Many moths, however, fly by day. In Europe, the hummingbird hawk-moth hovers at garden flowers in bright sunshine, and burnet moths visit meadow flowers. The sunset moth of Madagascar is a day-flier with iridescent wings often mistaken for a butterfly’s.

The reverse also exists. The Hedylidae, a small family of moth-like butterflies from Central and South America, fly at night. Some of them even have ears that detect the ultrasonic calls of hunting bats, a defense better known from moths.

Chrysalis versus cocoon

Both groups pass through a pupal stage, but they protect it differently. A butterfly caterpillar usually forms a chrysalis, a pupa with a hard outer skin, often hanging from a twig or leaf by a small hook. It is not wrapped in silk. The whole process is explained in how does a caterpillar turn into a butterfly?

Many moth caterpillars spin a cocoon, a silk case around the pupa. The luna moth wraps its cocoon in dead leaves on the ground, and the domesticated silkworm’s cocoon is the source of silk. Many other moths, including most hawk-moths, skip the cocoon and pupate in a chamber in the soil.

Exceptions exist here too: Apollo butterflies of mountain regions spin a loose silk cocoon among leaf litter, and many skippers pupate inside rolled leaves tied with silk.

Bodies, colors and size

Moths are often stouter and furrier than butterflies. The thick coat of hair-like scales helps night-flying moths keep their flight muscles warm on cool evenings. Butterflies tend to be slimmer, although skippers are notably chunky.

Many moths wear camouflage browns and grays that hide them on bark or dead leaves during the day, while butterflies are often brightly colored to attract mates or warn predators. Yet some moths, such as the luna moth, the rosy maple moth and the tiger moths, are as colorful as any butterfly, and many butterflies have drab, leaf-like undersides.

Both groups produce giants. The largest butterfly, Queen Alexandra’s birdwing of Papua New Guinea, reaches a wingspan of about 28 cm (11 in), while the white witch moth of Central and South America has the widest known wingspan of any insect, up to about 30 cm (12 in). See what is the largest moth in the world? At the other end of the scale, the tiniest moths have wingspans of only a few millimeters.

Are butterflies really moths?

In evolutionary terms, butterflies are a branch of the moth family tree. Large DNA studies, including a 2019 analysis of more than 200 species, show that butterflies sit inside the moth family tree: some moth families are more closely related to butterflies than they are to other moths. Dated family trees suggest that butterflies arose roughly 100 million years ago from night-flying, moth-like ancestors.

This means “moth” is not a natural group in the way “butterfly” is. It is simply a name for all Lepidoptera that are not butterflies. Biologists still use the everyday words, because they are useful, but they recognize that the line between the two is a matter of convenience rather than a deep split.

Which is more common?

Moths outnumber butterflies almost everywhere. In Britain, about 59 butterfly species are recorded regularly, compared with around 2,500 species of moths. Because most moths fly at night and many are small and well camouflaged, people simply notice them less.

Both groups play important roles as pollinators and as food for birds, bats and other animals. A garden at night may hold more moth species than the daytime garden holds butterflies.