What’s the difference between a moth and a butterfly? | Digital Collections Programme

We are currently digitising the Madagascan Lepidoptera collection, a project that has been supported by John Franks and the Charles Wolfson Charitable Trust.

madagascan drawers
A drawer of Madagascan type specimens

The specimens imaged are ‘Types’ – specimens from which the relevant species was named and described.

These ‘type’ specimens have both scientific and historical significance, often bearing labels in original handwriting, so releasing them openly means that more scientists have access to this resource across the world.

So far we have digitally imaged around 1,200 Lepidoptera from the Madagascan collection, comprising about 900 moths and 300 butterflies. These digitised specimens will join our previously digitised British and Irish Moths and Butterflies, which can be accessed on the Data Portal.

For the past year we have been posting news from the Lepidoptera collection every Monday to link into the #MothMonday hashtag. We have also released Lepidoptera blog posts and content in relation to Springwatch and Autumnwatch. We noticed that we often get similar questions for our Lepidoptera curators, so we thought we would find out the answers for you once and for all, illustrated with examples from the Madagascan digitisation project. So, if you want to know what the difference is between a moth and a butterfly, you’re in the right place…

Over 90% of all Lepidoptera are moths, and there are more species of moths than butterflies, but why?

This is a tricky question, because it depends on the definition of both words. The term ‘butterflies’ refers today to six of the 140 lepidopteran families. Butterflies form an evolutionarily natural grouping, or ‘super family’, called Papilionoidea, whereas the remaining moths form a further 42 super families. There are around 18,000 described butterfly species, and around 140,000 moths species.

The majority of butterflies fly by day. From a predation point of view, this is more risky strategy than being nocturnal like most moths. This might explain the difference in species numbers between butterflies and moths. We can look at the six families of butterflies that make up only 6-9% of the Lepidoptera population below.

The six butterfly families 

1) Madagascan butterflies

From top left to bottom right: 1. Papilio mangoura, a Madagascan Papilionidae; 2. Eurema floricola, a Madagascan Pieridae; 3. Heteropsis drepana, a Madagascan Mymphalidae; 4. Deudorix wardii, a Madagascan Lycaenidae; 5. An illustration of Saribia tepahi by Boisduval (1833); 6. Perrotia albimacula, a Madagascan Hesperiidae.

  1. Swallowtails (Papilionidae)

The swallowtails have six walking legs; the name swallowtail refers to the tail-like appendages on the hindwings of many species in this family.

  1. Whites and sulphurs (Pieridae)

The Pieridae are small to medium butterflies. They have six walking legs like Papilionidae, but no tails on the hindwings. They often have pale white or yellow wings with markings in black or orange.

  1. Brush-footed butterflies (Nymphalidae)

The brush-footed butterflies are the largest family of butterflies, with > 6,000 species described worldwide. Their first pair of legs are reduced in size and used to taste their food. Only two pairs of legs are used for walking and resting. In Madagascar, there is an astounding diversity of Mymphalidae, over a third of the described butterfly fauna. Heteropsis drepana is a beautiful example with wingtips that imitate dried leaves at rest.

  1. Gossamer-winged (Lycaenidae)

The name “gossamer-winged” refers to the sheer appearance of the wings, which are often streaked with bright colours. Many species are metallic blue or coppery on the upperside, but Spalgis tintinga has – unusually – a white background and its caterpillar is a carnivore of scale insects.

  1. Metalmarks (Riodinidae)

Metalmarks get their name from the metallic-looking spots that often adorn their wings, but the name is not apt for Madagascar, as in the case of Saribia, they are not metallic, but have prominent tails on the hindwings. When landing on a leaf they have a fascinating, pirouetting behaviour. There are a handful of described species, some of which closely resemble each other.

  1. Skippers (Hesperiidae)

The name skipper refers to their movement, a quick, skipping flight from flower to flower. Unlike the usually strongly “clubbed” antennae of butterflies, those of skippers end in a crochet-like hook. There are many skippers uniquely endemic to the native forests that remain in Madagascar.

What’s the difference between a moth and a butterfly?

Generally speaking although there are many exceptions, butterflies tend to fly by day and are often brightly coloured. They have a thickened club or hook on the tip of the antennae. Butterflies tend to hold their wings together above their body when resting. Butterfly wings are not linked together, whereas moth wings are usually linked with a bristle-like structure called a frenulum.

2) sensational butterflies
Madagascan moon moths (Argema mittrei) in the Museum’s Sensational Butterflies exhibition.

Moths have simple thread-like or ‘feathery’ antenna without a club. They hold wings flat when resting. As moths fly at night, bats often hunt them – some moths produce distractive noises back to bats which confuses their echo location methods while hunting. The Madagascan moon moth (Argema mittrei) has long tails, believed to be used in defence against attackers.

Alessandro Giusti, a Curator of Lepidoptera at the Museum, explains that “It seems that spinning tails behind a flying moth interfere with a bat’s echolocation and help lure bat attacks to these elongated parts of the hindwings… The bat will attack the tails rather than more vulnerable parts of the body.”

And here’s Alessandro explaining the difference between moths and butterflies in person:

There are exceptions to the rule:

Rothia arrosa is a colourful and ‘butterfly looking’ moth with clubbed antennae, like a butterfly. However it’s family name is Noctouidea – latin for night owl and despite its bright colour it is a night flying moth.

Hylemera euphrantica is a geometrid moth from Madagascar. Geometrids have slender abdomens and broad wings which are usually held flat with the hind wings visible. As such, they appear rather butterfly-like; however the majority fly at night, they possess a frenulum to link the wings, and the antennae of the males are often feathered.

While there are many differences between butterflies and moths, the main reason why moths are more numerous is because they represent more diversity. When thinking about the difference between a moth and a butterfly, it could be easier to think instead of whether a particular example belongs to the one butterfly super family, or the many diverse super families of moth.

To read about our Madagascan digitisation project please visit our earlier blog. To hear more stories behind the Lepidoptera collection you can follow our #MothMonday content on Twitter or keep up to date with the Museum’s digitisation projects on the website.