Butterflies and Moths: Life Written on Wings

The Natural History Museum

Butterflies have captured the human imagination like no other insects. And we have collected butterflies in nets like no other insects. The Natural History Museum's collection of 10 million Lepidoptera - butterflies and moths - is the largest distinct collection in these buildings. This gallery showcases our collection and the stories that Lepidoptera tell about the world around us. These specimens are windows into evolution, ecology, natural history and the enthusiasm of collectors.

Different scales
'Lepidoptera' derives from the Greek words for 'scaly wings', and it is these scales that render butterflies and moths so distinctive. Scales are individually tiny, but combining thousands produces their vivid patterns. The sum of all these specimens is a research collection of global importance.

The wings of the purple emperor, Apatura iris, are vivid purple-blue from some angles and brown from other angles. This may have given rise to the genus name, from the Greek 'apatao' - 'to deceive'. Shifting, metallic colours such as this example derive from structural properties of the scales, which refract light at certain wavelengths.

The eye spot of the peacock butterfly, Inachis io, is composed of hundreds of scales of different colours, creating one larger image that other organisms, including humans, perceive as an eye spot.

On small moths, individual scales can look huge. This is a close-up of the head of a gelechiid moth, Deltophora phyllanthicella. It was only described in 2016 by taxonomists including Dr Klaus Sattler of the Natural History Museum.

Harmonic scales: some male hawkmoths produce ultrasonic squeaks that disrupt the echolocation calls of bats. These squeaks are achieved by scraping stridulatory scales - modified scales on the genitalia - against abdominal scales.

Scales are involved in producing scents. Some butterflies have a 'sex brand', a patch of specialised androconial scales of the male fore wing that helps disperse pheromones emitted from tiny organs on the wings. The pattern of these scales makes it relatively easy to distinguish the males of the small skipper (Thymelicus sylvestris) (left) and Essex skipper (Thymelicus lineola) (right). Females are more difficult to separate, however, unless you get a good view of the underside of the antenna tip.

Some moths have tails – and not just the tail-like projections from the wings, which give the swallowtail its name. Some hawkmoths such as this Cephonodes kingii have manouevrable tails of specialised scales that can be flexed by the abdominal muscles, increasing the agility of the moth in flight.

Within a lepidopteran wing pattern is a complicated network of veins that delimit cells. This can be seen most clearly on the mostly naked wing of a glasswing butterfly, Greta morgane oto. The patterns of wing veins have been used to infer the evolution of the Lepidoptera, as well as other insect orders.

Written on the wings
Evolutionary history is written on the wings of moths and butterflies. By studying variation in wing patterns, evolutionary biologists have made breakthroughs in the fields of evolution and developmental biology.

The peppered moth, Biston betularia, is the most famous example of change in the frequency of colour patterns due to changes in the environment. In this case, the number of dark individuals increased when industrial pollution killed off lichens on tree trunks and deposited soot on the trunks. Geneticist Bernard Kettlewell carried out groundbreaking experiments on the genetics of colour morphs. Shown here are some of his bred specimens and his original notes. The story has become complex with the realisation that peppered moths don't normally rest on tree trunks. The genetics of this story are also complicated by the fact that there are two dark morph genotypes.

The African mocker swallowtail, Papilio dardanus, has been a model for evolutionary biologists for many years. Appearing in a number of morphs across different habitats, and with females mimicking less palatable species, one of the many intriguing stories involving this species concerns the difference between females and males. Differing selection pressures on the sexes result in females with wildly varying wing and mimicry patterns.

A small brown butterfly, the squinting bush brown (Bicyclus anynana), is the subject of a huge body of research investigating the effects of environment on the different colour morphs, including the appearance of eye spots and the influence of sexual selection in stabilizing wing patterns. From its African home, Bicyclus anynana has become a popular laboratory organism and is amongst an increasing number of butterflies to have had its entire genome sequenced.

The human eye sees alphabets in nature. Many butterfly and moth names reference letters and numbers that can be seen on their wings, such as Autographa gamma (in English the 'silver Y').

If you have been light-trapping in Britain, you may have seen a moth land on a white sheet and transform into a piece of twig. The buff-tip, Phalera bucephala, is one of many species that have evolved to disappear into the background. Species such as the buff-tip look vastly different when pinned with wings outspread - hence names that refer to pale patches on the body rather than directly referencing their outlandish camouflage.

Lepidoptera wings easily tear and their scales rub off, as anybody who has prepared specimens will attest. Unlike with bird wings, there are no feathers to be replaced - these wings need to last the life of the adult butterfly or moth. They nevertheless often transport butterflies and moths over long distances. 

The painted lady, Vanessa cardui, undertakes one of the most remarkable migrations of European butterflies. When populations explode in North Africa, huge numbers move northwards. But it is not these individuals that reach us in Britain. Successive generations breed over the course of the summer, with offspring venturing further north. Then, remarkably, the butterflies emerging from eggs laid in Britain reverse this journey and move south, mirroring their ancestors from earlier in the year. Many details of this migration have been pieced together through citizen science, recording butterflies and their movements, and more high-tech use of radar and other techniques for tracking insect movements. These specimens demonstrate the wear and tear that accumulates over a butterfly's relatively brief life.

The most renowned butterfly migrant is the monarch, Danaus plexippus, journeying from large areas of North America to spend winter in their millions in Mexico and, to a lesser extent, California. The monarch's embarking on both the outward and return journeys is also highly unusual in the butterfly world.

Monarchs usually travel vast distances, and individuals even sometimes make it across the Atlantic. They have also colonised the Canary Islands - reproducing in isolation on these islands, monarchs cannot yet be distinguished from their North American ancestors but maybe will be in the future.

Agrotis infusa, the bogong moth, also migrates, but to favoured summering grounds, where they wait out the heat and drought. During its migration, huge numbers of this species arrive at the Australian parliament buildings some years, attracted by the bright lights.

Some tropical uraniid moths undertake spectacular seasonal movements. Urania fulgens has sedentary and migratory phases, in response to rainfall patterns in its homeland of Taiwan.

Life cycles - egg to imago
The adult insect, called the imago, is the reproductive phase of a complicated life cycle. Undergoing complete metamorphosis, many species spend far longer in their immature phases, as an egg, larva and pupa (or chrysalis). Larvae exploit a wealth of feeding opportunities.

Caterpillars are notoriously difficult to prepare as attractive pinned specimens. Unlike the adults, they are soft and they collapse and decay. The Museum has a relatively small collection of blown caterpillars, such as this swallowtail, Papilio machaon, whose insides have been squeezed out and the outer cuticle inflated and dried. It is more common nowadays to preserve larvae in alcohol.

Larvae are potentially appetising to predators. Spines and toxic chemicals have evolved on numerous occasions to deter predators. This South American saturniid caterpillar, of the subfamily Hemileucinae, is toxic enough to be potentially lethal to humans.

In Britain, the lime hawkmoth, Mimas tiliae, almost always lives up to its name by eating the leaves of lime trees (Tilia species). But, further south in Europe, it will also happily eat birches (Betula). One theory is that it takes longer for the larvae to develop when eating relatively less nutritious birch leaves, so there simply isn't time in the short British summer for the life cycle to complete.

It can take a long time for a caterpillar to develop when the food isn't sufficiently nutritious and the summer is all too brief. The arctiine moth Acsala anomala inhabits subarctic areas of North America, where it typically takes the larvae several years to complete their feeding.

Sometimes caterpillars offer more reliable identification features than adult moths. The grey dagger (left) and dark dagger (right), Acronicta psi and Acronicta tridens, are virtually identical as adults but easily distinguishable as larvae.

Millennia ago, people harnessed the silk-spinning abilities of a moth. The silk moth is a peculiar creature, but the ability to spin silk is common to many species, for constructing cocoons to protect their pupae, and sometimes webs to protect larvae.

The silk moth, Bombyx mori, was domesticated in China millennia ago and is responsible for the vast majority of silk that we use. It produces silk to construct its cocoon. Bombyx mori has close relatives in the wild, but this species is now only known in domestication and cannot be found on its food-plant, mulberry, in the wild. After countless generations of silk moths having been bred in captivity, the larvae cannot locate food unless they are placed directly on the leaves, and the adults now have useless wings.

Caterpillars produce silk from spinnerets in their mouthparts. Silk from the silk moth is prized because it is laid down in a fine, continuous single strand to weave a cocoon. Moths that make cocoons underground tend to apply silk in large sweeps, like a plasterer, and their silk is unsuitable for fabrics.

Some other moths are exploited for their 'wild silk', particularly in India. Cocoons of species such as Antheraea paphia are harvested after the adult emerges, whereas Bombyx mori cocoons are killed and the entire cocoon unravelled as one long silk thread.

The tough brown cocoon of the oak eggar, Lasiocampa quercus, is typical of many moths that pupate in the open. The outer layers comprise coarse silk threads, while the inner layers are tightly woven. On the inner surface, a shiny layer secreted by the larva waterproofs the cocoon.

Pupae are potentially vulnerable to all sorts of predators. Many Lepidoptera pupate while concealed, or spin tough cocoons. Urodus parvula spins this beautiful, intricate hammock of a cocoon. Belying the delicate appearance, many spines are incorporated to deter predators.

Silk is also spun by larvae of some species for protection when feeding or resting in the day. The spindle ermine, Yponomeuta evonymella, feeds communally in webs found on spindle bushes. Some of these webs can be spectacular, with many metres of bushes entirely shrouded by silk.

Food and foes
Silk moth pupae are eaten in large quantities in China. They're not the only economically important Lepidoptera on the menu: in many countries, caterpillars are an important source of protein and are often delicacies. Caterpillars are also food, in much larger numbers, for a great many species of parasitoid wasps as well as all manner of predators. Despite these limits on numbers, some species of moths and butterflies are still economically important pests of food crops and forestry.

Silk moth (Bombyx mori) pupae are commonly eaten as they are killed, and the silk can be harvested before the moth emerges and breaks the single silk strand. An African silk moth, Gonimbrasia belina, often known as the mopane worm, is also eaten in large quantities and can be bought by the bucketful in markets.

The horse-chestnut leafminer, Cameraria ohridella, was described as a species new to science in 1986. In recent years it has spread over much of Europe and causes significant damage to horse-chestnut leaves.

The origins of Cameraria ohridella were a mystery until herbarium samples of horse-chestnut leaves revealed that the moth had been living in the Balkans since the nineteenth century. The species presumably originated there, overlooked until it started stretching its wings and moving northwards. The adult is tiny but beautiful. Although a strong flyer, Cameraria ohridella is thought to have been inadvertently moved by vehicles over long distances.

The swallowtail, Papilio machaon, is the only British representative of a widespread family, the Papilionidae. Unlike its European relatives, the British population eats only milk parsley, Peucedanum palustre, in a few fens of Norfolk, although it used to be more widespread. Despite its low numbers, its specialist parasitoid, the ichneumonid Trogus lapidator, has clung on in Britain. Parasites and parasitoids are often seen as nuisances at best, but a healthy ecosystem should have a wide spectrum of parasites. Pupae that were parasitised can be recognised as the Trogus adult makes a neat emergence hole through the pupal wing case.

Specimens found in museum collections are at risk from pest moths. This pair of antlers is studded with the pupal cases of tineid moths, Ceratophaga vastella, which have been eating it.

Not just clothes moths
The word 'moth' is often associated with clothes moths and the damage they cause. However, only a small number of species eat our clothes and carpets. Here are the clothes moths as well as some of their lesser-known relatives, which are often brilliantly patterned and come with fascinating life histories.

The usual suspect, responsible for many domestic clothes moth infestations, is the case-bearing clothes moth, Tinea pelionella. Its larvae feed in secluded spots on natural fibres. They require a warm climate and do well in centrally heated homes in Britain, especially given the recent mild winters.

A close relative of the case-bearing clothes moth, Tinea semifulvella is a common outdoors resident in Britain, where it feeds in bird nests - probably the original homes of pest species.

The psychids, often known as bagworms, are near to clothes moths on the evolutionary tree. Their larvae live in elaborately constructed cases.

Many species of psychids have wingless females that never leave their cases, laying eggs on the case after mating with the winged males.

The white-shouldered house moth, Endrosis sarcitrella, is another rather common inhabitant of houses, eating carpets and other natural fibres. This belongs to a different family to the clothes moths, the Oecophoridae.

Other oecophorids can be conspicuously beautiful. The relatively common Esperia sulphurella eats dead wood.

Oecophora bractella is now a rare species in Britain, confined to ancient woodlands where the larvae eat dead wood.

The most primitive moth lifestyle is represented by the archaic family Micropterygidae. Unlike all other Lepidoptera, micropterygid adults have mandibles with which they can chew pollen grains. Their larvae seem to eat leaf particles in the leaf litter or possibly fungal hyphae.

Insects of a small island
A considerable amount of information is available on specimen labels and written on the wings of the specimens themselves. The Natural History Museum is liberating these data through its digital collections programme, which includes photographing specimens and labels. For the UK butterflies and moths, with information now available through the Museum's data portal, this programme is already transforming our understanding of butterfly distributions and flight times over the decades. The effects of a changing climate and a radically changed landscape have brought profound changes in both emergence times of our butterflies and moths as well as less expected changes in their ecology.

With the digitisation of our entire collection of British silver-spotted skippers, Hesperia comma, the Museum's data fill former gaps in our knowledge. With a warming climate, the species is now emerging earlier and growing to a larger adult size.

The large heath, Coenonympha tullia, varies across its limited British range. Northern Scottish specimens have tiny spots or are entirely unspotted, while at the southern edge of their range in lowland Northern England, they are strongly spotted. Will this spotty pattern change over time? Genetic work on some British butterflies has shown that some genotypes are only present in museum collections, demonstrating that we have lost diversity within species as their populations have declined.

Through the enthusiastic collecting of a few naturalists, we have an unparalleled view of variation within discrete populations of a butterfly. The chalkhill blue, Polyommatus coridon, is rather local in Britain and restricted to one foodplant, the horseshoe vetch (Hippocrepis comosa). But where it occurs, populations can be sizeable and males conspicuous. A large series of specimens gives an idea of the variation within a species, which here include a hybrid with the Adonis blue, Polyommatus bellargus, and a rare gynandromorph - part female, part male.

The swallowtail (Papilio machaon) in Britain looks different from its European cousins of the same species. This reflects variations in habitat and foodplants.

The black-veined white, Aporia crataegi, was formerly relatively widespread in England, but was extinct by 1925 for poorly understood reasons.

Despite its English name, the New Forest burnet, Zygaena viciae, was last seen in the New Forest in 1927. Feared extinct in Britain, one population was eventually found on a ledge of a mountain slope in Scotland. The population has increased since its discovery in the 1960s but is still very localised.

Amassing the Museum's collections relies for the most part on the endeavours of committed amateur entomologists. Without the efforts of armies of collectors and recorders, we would have very little evidence for researchers to uncover change in the fortunes of our diverse flora and fauna. This chart shows the weekend spikes in collection dates for the orange-tips (Anthocharis cardamines) found in our collection.

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