It is possible of course to read too much into the “colour for survival” theme. There doesn’t have to be a survival-related reason for every nuance of pattern or colour. After all what possible difference could it make if a caterpillar has a brown head instead of a black one ? Having said this however it is quite obvious that a butterfly that is camouflaged as a dead leaf has a considerably higher chance of avoiding predation than one that is not.

Butterflies have short lives – typically less than 2 weeks as an adult, so they need to quickly locate mates. Many species lose their attraction to the opposite sex within just a day or two of emergence because their pheromones become exhausted. Rapid mate recognition is therefore vital.

The first stage in the recognition process consists of intercepting any flying object of roughly the same size and colour as their own species – in the neotropics for example it is easy to attract blue Morpho butterflies by waving a piece of blue foil in the air.

Purple Emperor Apatura iris, male – Adrian Hoskins

In many genera e.g. Apatura, Morpho and Doxocopa the wings of males have a highly reflective blue sheen. During flight their wings glint brilliantly in the sunshine and probably play a major role in mate location and recognition.

Once initial contact has been made, a combination of olfactory and visual factors hold the interest of both sexes as a precursor to the courtship ritual. Visual stimuli include holding the wings or body at particular angles, flicking the wings, or simply displaying the patterns by opening the wings.

During the courtship process a series of exchanges takes place during which various stimuli trigger either negative or positive responses. A negative response might indicate that the potential mate was not of the same species, or was unwilling to mate – females of many Pierids for example signal an unwillingness to mate by raising their abdomen and outspreading their wings.

A positive response invariably triggers another visual, olfactory and tactile stimulus, which leads to another response. By going through these stimulus / response sequences the butterflies are able to determine firstly that they are of the same species, then that they of opposite sexes, and finally that both are ready and willing to to mate. In some species this process is very brief, but in others such as the Small Tortoiseshell Aglais urticae, it is protracted and may take several hours during which the male doggedly follows the female from place to place, persuading her to copulate.

Small Tortoiseshell Aglais urticae – Adrian Hoskins

Male butterflies will usually intercept both sexes of their own species. The purpose of male-male sorties is to challenge and oust an intruding male from the territory of another, thereby increasing the territory owner’s chances of success with any female that passes by.

Males also “know” that they can often find food by following other males : In tropical regions males of many species visit sandbanks and damp paths to indulge in “mud-puddling”. Their purpose is to imbibe mineralised water, from which they obtain vital salts. These are passed to females during copulation and are believed to be essential for the production of fertile eggs.

Typically just one or two males will chance upon a suitable feeding spot, but other butterflies flying past seem able to recognise their brethren on the ground, and swoop down to join them. The bright patch of colourful butterflies quickly becomes a magnet to every passing male of the same species.

Often several different species may be present at these feeding places. In these circumstances one might expect each species to be spread randomly within a large group, but in fact each butterfly polarises very strongly to it’s own brethren, so that each species congregates as a discrete group.

In calm weather the butterflies in each group are positioned randomly, but on riverbanks there is usually a constant gentle breeze, so all the butterflies in each group tend to face into the breeze as this way they are less likely to be blown about and lose their feeding spot to a competitor.

Phoebis argante and Rhabdodryas trite aggregating at Rio Shima, Satipo, Peru – Adrian Hoskins

Butterflies use many means to hide themselves from predators. Sometimes, as with the neotropical metalmarks ( Riodinidae ), they simply hide under leaves, out of sight. Most other species rest in more open situations though, and conceal themselves using techniques such as camouflage, disguise, disruptive coloration or transparency.

The boundary between camouflage and disguise is hard to define, but camouflage is generally considered to describe something with a colour, pattern and texture that enables it to blend well against a natural background or substrate. Butterflies rest on many different substrates including foliage, soil, rocks and tree trunks – and various species possess colours and patterns which match each of these backgrounds.

Disguise on the other hand describes a butterfly or moth that has a similar appearance to another natural object, such as a leaf or flower. Moths often have very effective disguises – some which rest on tree trunks resemble bits of lichen, others resemble bits of broken twig. The caterpillars of many Geometrid moths look exactly like twigs, and even have small projecting false “thorns”.

Camouflage

Amongst British butterflies the Orange tip Anthocharis cardamines is a good example, difficult to spot when at rest on the white flowers of garlic mustard.

Anthocharis cardamines, camouflaged at rest on garlic mustard flowers – Adrian Hoskins

Disguise

The Brimstone Gonepteryx rhamni, is a superb example of disguise, being coloured and shaped like a living leaf, complete with raised “veins”.

Brimstone Gonepteryx rhamni, perfectly disguised as a leaf – Adrian Hoskins

In the tropics there are many species which are disguised as dead brown leaves – examples include the Leaf butterfly Kallima inachus from India, and the Memphis and Marpesia Leafwing butterflies of South America.

Zaretis itys, a Peruvian species convincingly disguised as a dead leaf – Adrian Hoskins

Disruptive coloration

This term is used to describe the way in which a butterfly or moth’s appearance is visually broken up, usually by means of mottling and / or prominent lines.

The Angle Shades moth Phlogophora meticulosa is a good example – it is equally well concealed when settled amongst dead vegetation or fallen branches.

Predators – particularly birds, use a “search image” to locate resting moths. They look out for a “moth shaped” object, but the disruptive pattern of the Angle Shades breaks up it’s outline and foils the bird’s search image.

Angle Shades moth Phlogophora meticulosa, Hampshire, England – Adrian Hoskins

Hylephila peruana, a skipper from Peru. The disruptive patterning makes it very difficult to detect amongst the dry grasslands of it’s habitat in the Andes – Adrian Hoskins

Grayling Hipparchia semele, perfectly disguised at rest on dead wood – Adrian Hoskins

Transparency

The colours of butterflies are produced either by pigments in the wing-scales, or structurally by light refracting on prism-like ridges on the surface of the scales. Some species however are very thinly scaled or lack wing scales almost entirely, revealing the transparent membrane of the wings.

Butterflies which use transparency to conceal themselves include Ithomiine Glasswings and certain neotropical Satyrines such as Cithaerias pireta and Dulcedo polita. There are also representatives from other families, e.g. Chorinea ( Riodinidae ) and Lamproptera ( Papilionidae ).

Cithaerias pireta aurora, Cocha Camunga, Rio Madre de Dios, Peru – Adrian Hoskins

Vein structure of a transparent Satyrine butterfly Haetera piera – Tony Hoare

Altinote dicaeus callianira – it’s distinct pattern advertises it’s unpalatability – Adrian Hoskins

Aposematic colouration is a term used to describe colours and / or patterns that act as a warning to predators that a potential prey species is unpalatable, toxic or dangerous.

Various studies have shown that all vertebrates including insectivorous birds associate greens and blues with safety, and inherently regard red, orange, yellow and white as signs of danger. It is also widely accepted that patterns incorporating stripes or spots draw attention to objects.

Consequently it is no surprise to find that toxic or unpalatable butterflies have evolved colour schemes that reflect these facts, in order to “label” themselves as being unpleasant to eat, and thereby dissuade birds from attacking them. Equally it is unsurprising that a significant number of palatable species have evolved which mimic the patterns of toxic species, in order to trick birds into leaving them alone.

Birds can remember the colours and patterns of butterflies, and associate them with pleasurable or unpleasant experiences. If a bird pecks at a toxic butterfly it finds the taste very unpleasant, and is likely to suffer consequences including vomiting, nausea and visual disturbance. Experiments with various insectivorous birds have shown that if they suffer this experience they then avoid eating similarly coloured butterflies for several hours or days. Periodically they re-sample aposematically coloured butterflies, thereby reaffirming their unpalatability.

It has also been demonstrated that certain lizards e.g. those in the neotropical genus Amieva learn to recognise and avoid eating aposematic butterflies. Further study will quite possibly demonstrate that chameleons, tree frogs and other vertebrate insectivores react similarly.

Diematic patterns

Defensive markings which have the effect of startling or frightening potential predators are known as diematic patterns.

The commonest form of diematic defence is the use of ocelli. Usually these take the form of a pair of false-eye markings which can frighten away a predator, or at least startle it long enough for the insect to make it’s escape. In many butterflies and moths these ocelli are highly conspicuous and simulate the eyes of monkeys or raptors. Examples include Automeris Bullseye moths, Smerinthus Eyed Hawkmoths and the Peacock butterfly Inachis io. In others the ocelli are smaller and simulate the eyes of snakes or lizards. Field observations and laboratory experiments have confirmed that many insectivorous birds are deterred by aposematic and diematic markings.

In a study by Stockholm University, the ocelli of 20 Peacock butterflies Inachis io were blanked out with a marker pen. When exposed to blue tits, 13 of them were attacked and eaten. A control group of 34 Peacocks with intact ocelli fared much better – only a single butterfly was attacked. It can be concluded that in 97% of encounters with blue tits, the ocelli are effective as a deterrent.

Inachis io – very beautiful to human eyes, but frightening to a small bird – Adrian Hoskins

The neotropical Bullseye moths such as Automeris liberia, keep their ocelli hidden most of the time beneath their cryptically patterned “dead leaf” forewings. If disturbed they immediately drop to the ground and twitch rhythmically, drawing maximum attention to the ocelli. The appearance is quite fearsome, and more than enough to deter a bird from attacking.

Automeris liberia, Ecuador – Steve Ife

Diematic mimicry is quite a common form of defence in caterpillars as well as in adult butterflies and moths. The larvae of many Swallowtail species including Papilio polymnester and Papilio troilus have a pair of false eye-spots on the thoracic segments. Many hawkmoth larvae such as Deilephila elpenor and Hippotion celerio employ the same strategy. When alarmed the larvae of these species puff up the thoracic segments causing the eye-spots to expand. This is considered to be a form of diematic defence in which the larvae are mimicking the heads of snakes.

Snake mimicry is also found in adult Atlas moths in the genera Attacus and Rothschildia. In these species the forewing apex is lobed, and bears markings corresponding to the eyes and mouth of a snake. The illusion is enhanced by rhythmic movements of the wings which draw attention to the snake-head markings.

Snake-head markings on apex of Giant Atlas moth Attacus atlas – Gan Cheong Weei

Decoys to distract birds

Often the frightening effect of diematic markings is only temporary. Having gotten over the initial shock a bird may resume it’s attack. In such circumstances the ocelli on the butterfly’s wings take on a secondary defence role, diverting and confusing the predator :

When a bird attacks a butterfly it naturally focuses it’s aim on an obvious target area. The presence of a decoy target such as a false eye diverts the attack away from the butterfly’s body, towards the wing borders. Usually this results in nothing more than a small chunk being pecked out of the wing, and the insect escapes virtually unharmed.

It is not unusual to find ocelli-marked butterflies which have had chunks pecked out of their wings by birds. Butterflies are able to fly and go about their lives with quite large pieces missing from their wings, but an attack on their body would be fatal.

Sometimes the ocelli are huge, as in the neotropical Owl butterfly Caligo teucer, but even the small ocelli on species such as the Gatekeeper Pyronia tithonus are enough to divert a bird attack away from the butterfly’s body.

Caligo teucer,  Peru -Adrian Hoskins

The Zebra Teaser Arawacus separata and many other butterflies in the subfamily Theclinae have wings that are marked with bright streaks which lead the eye away from their head, and towards antennae-like tails on their hindwings. In many species there is also a red or black spot near the tail, which simulates an eye.

The overall effect is to create the illusion of a “false head”, and to give the butterfly a back-to-front appearance. This is further enhanced by the butterfly’s habit of immediately turning to face the other way as soon as it lands on a flower or leaf. It is also likely to dip it’s real head, and raise the false head. Periodically, it oscillates the hindwings, causing the false-antennae tails to wriggle.

An attacking bird always tries to anticipate the escape route of it’s prey, so it aims it’s attack at a point fractionally in front of the head. The false head fools the bird into aiming behind the butterfly instead. The butterfly then darts off in the opposite direction to that which the bird expects, and makes it’s escape.

Arawacus separata – stripes give a back-to-front appearance, false antennae act as decoys

Patterns to confuse

Many butterflies have patterns which at first glance seem to serve no purpose. What for example would be the point of a striking and easily remembered pattern such as the chequered appearance of the Swallowtail Papilio machaon ?

Observing butterfly behaviour often reveals the answer to such riddles. The Swallowtail normally rests with it’s wings closed, but if it is disturbed it suddenly flicks them open in exactly the same manner as adopted by the Peacock and other ocelli-equipped species such as Bullseye Silkmoths or Eyed Hawkmoths. Furthermore, when alarmed the butterfly often moves the outspread wings in a jerky and almost threatening motion, as if to deliberately draw attention to itself.

It seems likely therefore that the pattern acts either to make the butterfly appear too large to eat, or that it simply confuses the bird – causing it’s eyes to wander all over the pattern while the bird tries to fathom out what it all means – Is it edible ? Is it dangerous ? Is it small enough to eat ? Which bit of it should I aim my beak at ? The bird may be so confused that it decides to abandon the attack, or the attack may simply be delayed long enough to allow the butterfly to escape.

The purpose of the crimson ocelli on the hindwings remains a mystery. They are not big enough to be scary, and their positioning close to the vulnerable body effectively rules out any possibility that they act as decoys or targets.

Papilio machaon flicks it’s wings open in a threatening manner if alarmed – Adrian Hoskins

Signalling danger to other butterflies

Warning colouration is generally assumed to be targeted directly at birds and other predators, but in the case of Panacea prola from Peru the purpose is quite different :

Large groups of males gather to feed on mineralised moisture on riverbanks. They bask when feeding, displaying their metallic blue uppersides, which help other passing males to locate them and home in on the feeding grounds.

A group of butterflies on the ground could easily be attacked by birds however, so the butterflies need to employ a defence strategy. Any kind of minor disturbance causes one or two butterflies to get twitchy, at which point they start fanning their wings nervously so that the bright red undersides are visible to the other butterflies.

Increased levels of nervousness cause them to fan their wings faster, which attracts the attention of further basking males, which join in the fanning activity. This “red for danger” signalling is a very effective alarm system. It quickly alerts all Panacea in the vicinity to any perceived threat, and allows them time to take evasive action before the threat becomes severe.

Panacea prola basks while feeding on mineralised water on a Peruvian riverbank – Adrian Hoskins

Panacea prola group wing-fanning to warn each other of potential danger – Adrian Hoskins

Flash Colouration

Many butterflies have a “now you see me, now you don’t” alternating display of a bright upperside and sombre underside. This is known as flash colouration.

An example is the South American Morpho helenor which has a brilliant iridescent blue upperside that makes it highly visible to predators as well as to potential mates. If alarmed, the butterfly will immediately land, snapping it’s wings shut so that only the dark brown underside is visible.

After landing however there is always the possibility that it might be spotted at rest by a pursuing bird, so then the secondary decoy-ocelli defence may help the butterfly to escape by diverting the birds beak away from the butterfly’s body and towards the wing edges.

Morpho helenor -Adrian Hoskins

Batesian Mimicry

The 19th century naturalist Henry Walter Bates realised that many species which were palatable to birds had uncannily similar patterns to unrelated toxic species. An often quoted example illustrated below is the palatable North American species Limenitis archippus which bears a quite remarkable resemblance to the highly toxic Monarch butterfly Danaus plexippus. Recent research however has shown that both of these species are unpalatable, thus they are Mullerian mimics , not Batesian mimics.

There are nevertheless numerous other examples of true Batesian mimicry such as the palatable Dismorphia and Heliconius species which mimic toxic Ithomiines; and the palatable Spicebush Swallowtail Papilio troilus which mimics the toxic Pipevine Swallowtail Battus philenor.

Bates published a scientific paper in 1862, in which he theorised that palatable species occasionally produced mutant forms with visual characteristics similar to toxic species. He believed that they would therefore be less likely to be killed by birds, and would pass on their characteristics to their offspring. He proposed that as a result of further mutations over the millennia, that palatable species had evolved to become almost identical to the toxic species.

This form of defence is widely known as Batesian mimicry. It is normally only effective because the toxic species far outnumber the non-toxic species. If the situation was reversed so that most of the butterflies attacked were palatable, the mimicry bluff would fail.

There are however circumstances where the mimic can outnumber the model, and the bluff will still work. An example is Eresia pelonia which produces several differently coloured forms or morphs, each mimicking a different toxic model e.g. the nominate subspecies E. pelonia pelonia is a mimic of the Ithomiine Callithomia alexirrhoe thornax; while subspecies Eresia pelonia callonia is a very close “copy” of Hypothyris mansuetus meterus. For any form of mimicry to work, both the mimic and the model must fly together in the same area, i.e. they must be sympatric.

Another example is the Mocker Swallowtail ( aka the Flying Handkerchief ) Papilio dardanus, which produces several mimetic forms. Such species are known as mimetic polymorphs. In the case of dardanus all males look identical, but the female produces several morphs. These correspond to a variety of different unpalatable models including Amauris niavius, Amauris echeria, Acraea poggei and Danaus chrysippus.

The reasons why only females produce polymorphs is poorly understood. Some biologists postulate that if males also produced polymorphs that certain morphs would be disadvantaged during male / male territorial conflicts. If this was the case the “losing” morph would end up holding lower quality territories, reducing their chances of intercepting females.

A further example is Perrhybris pamela – on the upperside of the wings the males are white with a black apex, but females are entirely different, patterned with bands of orange, yellow and black. The females are generally regarded as Batesian mimics of Ithomiines in the genus Mechanitis.

Perrhybris pamela, male, Rio Madre de Dios, Peru – Adrian Hoskins

Perrhybris pamela, female, Satipo, Peru – Adrian Hoskins

Mechanitis polymnia dorissides, Rio Pindayo, Peru – Adrian Hoskins

Müllerian mimicry

In 1879, Müller realised that there were also many cases where both the mimic and the model were unpalatable. When a bird catches any one of these butterflies, either model or mimic, and realises it is unpalatable or toxic, it quickly learns to keep away from all similarly patterned species.

This type of evolutionary “cooperation” is referred to as Müllerian mimicry, and is a very common phenomenon amongst the Ithomiinae, Danainae and Pieridae. Müller demonstrated mathematically that this form of mimicry is biased in favour of the scarcer species by a factor of the square of the ratio of species abundance. It is advantageous for there to be a large number of species involved in a Müllerian mimicry complex as it increases the power of the warning signal.

It is important to note that mimicry cannot be simply categorised into groups of distasteful models and Batesian or Mullerian mimics. There is actually a broad spectrum of palatability from species to species, and within any given species. Many butterflies only become unpalatable after sequestering toxins from plants, so when they first emerge they are palatable, but after a few days feeding they become unpalatable.

Birds and other predators must also vary considerably in what they find palatable – a tanager for example might be find a particular species of butterfly to be unpalatable, but a jacamar might find it quite acceptable.

The Tiger complex

A famous example of butterfly mimicry is the “tiger complex” – a group of about 200 neotropical species which all share a similar pattern of orange and yellow stripes on a black ground colour.

The complex includes many unpalatable Ithomiines such as Tithorea harmonia, Tithorea tarricina, Melinaea marsaeus & Forbestra equicola, unpalatable Danaines such as Lycorea pasinuntia, and several highly toxic day-flying moths from the Arctiid subfamily Pericopinae. It also includes many unrelated species that are considered to be palatable e.g. Heliconius ismenius, Heliconius hecale, Eueides isabella ( Heliconiinae ), Eresia eunice ( Nymphalinae ), Stalachtis calliope ( Riodinidae ), Consul fabius ( Charaxinae ) and Pterourus zagreus ( Papilioninae ).

Members of the tiger complex habitually aggregate in large numbers in damp gullies in the forest at the end of the dry season. It is at this time when they are very docile and easy prey for birds, that mimicry has its greatest potential as a defence mechanism. Any bird that suffers the unpleasant experience of tasting a member of the tiger-complex quickly learns to avoid attacking any similar looking species, and may even be capable of communicating their distasteful nature to other birds.

Eresia eunice ( Nymphalinae ) – Adrian Hoskins

Eueides isabella dissoluta ( Heliconiinae ) – Adrian Hoskins

Mimicry rings

Although the “tiger complex” is the most well known group of mimics and models in South America, there are a number of other mimicry rings. The “glasswing ring” is a group of largish transparent species that includes toxic Mullerian models in the Ithomiine genera Methona and Thyridia, a toxic Danaine Lycorea ilione, and a Batesian mimic – the palatable Dismorphiine Patia orise. The “orange ring” is comprised of a group of bright orange species including Marpesia petreus, Dryas iulia and Eueides aliphera.

Additionally there are several species pairs, the most well known of which is Heliconius erato and Heliconius melpomene. These species each produce 29 different geographically isolated subspecies. For each subspecies of erato, there is an equivalently patterned melpomene subspecies.

Why so many mimicry rings? The answer in the case of Ithomiines is vertical stratification of their forest habitats. The smaller glasswings regardless of genus tend to fly and utilise foodplants in the lower understorey. Tigers occupy the layer between about 2-4 metres above ground level. Other groups inhabit progressively higher layers, right up to the sub-canopy. In the case of genera such as Heliconius, which all tend to fly at roughly the same height, Mullerian mimicry complexes are apparently segregated horizontally by vegetation type.

Wasp mimicry

Many day-flying moths in the family Sesiidae have small transparent wings, and bodies banded in yellow and black. They bear a remarkable resemblance to wasps and hornets, and almost certainly escape predation as a result of their similarity to these stinging insects.

In the neotropical region there are dozens of Arctiid moth species in the genera Cosmosoma, which have transparent wings and boldly patterned red, orange, or yellow bodies. Most are nocturnal in behaviour and hide away amongst foliage in the daytime, so unlike members of the tiger-complex they don’t actively advertise their bold patterns to predators. It seems likely however that many are chanced upon by foraging birds, and that at such times their threatening appearance may save them from being devoured.

Cosmosoma species ( Arctiidae : Ctenuchini ), Manu cloudforest, Peru – Adrian Hoskins

Transformational mimicry

Mimicry is not just confined to adult butterflies and moths. Many palatable caterpillars also mimic unpalatable species. Caterpillars often change their appearance periodically after moulting, and it can happen that a caterpillar can mimic different models during different instars. Furthermore the adult butterfly or moth that ultimately results from that caterpillar could mimic yet another species. This is known as transformational mimicry. There are many other forms of mimicry known.

A note of caution

It is very easy to make assumptions about mimicry that may not prove valid. Not all examples of apparent mimicry are genuine cases. There are numerous examples of almost identical butterflies  occurring on opposite sides of the world. Such similarities cannot be attributed to mimicry, so how did they come about ?

The biological mechanisms & processes which generate wing patterns are fundamentally the same for all butterfly and moth species. It is therefore logical to assume that similarities will commonly occur amongst unrelated species, particularly where they evolve in similar habitats, where the mechanisms are affected by the same climatic and environmental factors.

It is obvious for example that many moth species across the world will have evolved to look like green leaves, or like bits of lichen or patches of tree bark, because these occur in all habitats, and the moths need a convincing camouflage when they settle on them. It is highly unlikely however that these near identical moths share common predators. Clearly these are simple cases of convergent evolution, but nothing whatsoever to do with mimicry.

Females however are more sedentary, tending to move very little until mated. Afterwards it may take them several days to lay all of their eggs so it is vital to minimise the likelihood of being attacked by a predator. Consequently it is advantageous for females to have drabber and more cryptic colouration.

Lysandra bellargus – male – Adrian Hoskins

Lysandra bellargus – female – Adrian Hoskins

Intrasexual competition

Another reason for the evolution of bright colourful males is that males are in competition with each other. Hingston argues that male butterflies engage in “psychological warfare, a battle of bravado, gesticulation and threat”, ‘their colours are their weapons”.

When males meet they usually indulge in fierce and often prolonged territorial battles. These waste valuable time and energy that would be better devoted to the pursuit of females. If a male could recognise other males from a distance he could avoid unnecessary battles, and hasten his chances of finding and mating with a female.

Bright colours are more easily seen from a distance, so it is feasible that males evolved brighter colours so they could recognise and avoid their own sex.

Eurybia molochina ( Riodinidae ) hiding beneath a leaf in the Peruvian rainforest – Adrian Hoskins

Many butterflies, both in the tropics and in temperate regions hide under leaves in overcast or rainy weather and roost beneath them at night. They are often patterned and coloured in such a way as to minimise detection by avian or mammalian predators at these times.

The Brimstone Gonepteryx rhamni for example is wonderfully camouflaged as it hangs beneath leaves of dogwood, buckthorn, bramble or ivy. Its wings are very leaf-like in shape and colour, and even have raised venation to simulate the veins of real leaves.

Brimstone Gonepteryx rhamni at roost beneath a dogwood, Hampshire, England – Adrian Hoskins

Pyrgines such as the Grizzled Skipper Pyrgus malvae usually roost at the top of dead flower-heads. The Dingy Skipper Erynnis tages behaves similarly, but takes things a stage further by wrapping it’s wings tightly around dead knapweed flowers, where it is almost impossible to see ( unless you are a very determined entomologist ! ).

Erynnis tages roosting on a dead knapweed flower, Hampshire, England – Adrian Hoskins

Polyommatine Blues usually roost at the top of grass heads, assuming a head-downwards posture. Satyrines such as Small Heath, Marbled White and Meadow Brown commonly roost on grass heads or flower heads. Checkerspots and Pearl-bordered Fritillaries adopt a similar tactic, often roosting on the flowers of rushes. Such strategies may seem a little difficult to understand, as the butterflies are easily spotted. The probable explanation is that they are choosing sites where they are out of reach of nocturnal predators such as mice.

Clossiana selene, ( Nymphalinae : Melitaeini ) seed-head, Wiltshire, England – Adrian Hoskins

This generation hibernates as adults and the winter colouration provides them with a more effective camouflage when they are hiding amongst dead brown leaves at the base of bushes and trees.

A more extreme example is Araschnia levana. Butterflies emerging in spring are orange with black spots, and resemble small Fritillaries. Summer brood butterflies however are black with prominent white bands and resemble miniature White Admirals. The formation of different wing patterns in the spring and summer broods is known to be triggered by temperature and length of day during the pupal stage. It is thought that such seasonal differences in appearance somehow give the species an advantage over predators.

Araschnia levana ( spring generation )	Araschnia levana ( summer generation )

In the case of certain tropical species such as Taygetis mermeria from the Amazon the advantages gained from having rainy season and dry season forms are more obvious. The butterflies spend long periods at rest, settled among leaf litter on the forest floor.

In the dry season the leaves are desiccated and orange-brown in colour, so the butterfly has evolved an orange-brown form which simulates the appearance of dead leaves, making it more difficult for predatory birds and lizards to find it. The wet season form is darker with olive-brown wings that are a more effective camouflage in the tropical summer when the foliage is greener and denser, and the shadows darker.

Taygetis mermeria, dry season form, Rio Madre de Dios, Peru – Adrian Hoskins

Taygetis mermeria, wet season form, Rio Madre de Dios, Peru – Adrian Hoskins

Visual mimicry is targeted at vertebrate predators – primarily birds and small reptiles. Butterflies and moths also use mimicry to protect themselves against insect predators, but in this instance chemical rather than visual mimicry is used.

Take for example the case of a caterpillar such as that of the Large Blue Maculinea arion, which is carnivorous during the latter part of its life, feeding on ant grubs within the underground nests of Myrmica sabuleti ants. The caterpillar had to evolve a way of protecting itself from the aggressive adult ants. It does this partly by appeasing the ants with ‘gifts’ of sugary fluids that it exudes from a dorsal ‘newcomers gland’, and partly by emitting chemical odours that fool the ants into thinking that the caterpillar is another ant.

The study of this pheromonal mimicry in butterflies is still in its infancy, but it will probably be found to be commonplace among Lycaenid butterflies, a high percentage of which spend the larval and pupal stages of their lifecycle in association with ants.

Cosmosoma myrodora, Manu cloudforest, 1400m, Peru – Adrian Hoskins

As in the case of thousands of other nocturnal species, males of the wasp mimic moth Cosmosoma myrodora are attracted by pheromones emitted by their females. As a myrodora male approaches a female, he hovers above her, and discharges a burst of very fine filaments which swirl in the air around her, and envelop her body.

American biologists Conner and Boada investigated the lifecycle and ecology of this moth. They found that Cosmosoma males are attracted to Eupatorium plants, and sequestered alkaloids from juices seeping from the stems. Such pyrrolizidine alkaloids are sequestered by a wide variety of butterfly genera including Ithomia, Pteronymia, Oleria, Lycorea and Danaus; and by several genera of moths in the family Arctiidae. The PAs stored in the bodies of the insects render them toxic or unpalatable to birds, and are a primary defence method in aposematic species.

The researchers found that in the case of Cosmosoma the toxins seemed to be directed mainly at predatory spiders. Moths caught in the webs of Nephila clavipes were cut free from the webs by the spider, but moths which had been deprived of the opportunity to sequester PAs were consumed.

Conner and Boada found that PAs were passed to females via the discharged filaments, and also via spermatophores delivered during copulation. The PA toxins conveyed to females were found to provide them with protection against predators during the following nights, enabling them to lay their eggs unmolested. It was also demonstrated that the toxins were passed to the eggs, and provided them with protection against ants, Coccinellid beetles ( ladybirds ) and Chrysopid larvae.

Stinging

Butterflies and moths do not sting in the sense that a wasp or bee does, but a significant number of species, particularly tropical ones, have spikes or setae (‘hairs’) which have urticating properties.  If touched, the hairs break and release formic acid, or strong alkaloids that can cause irritation or cause a skin rash on humans. This type of defence is found mainly in the caterpillars of the moth family Lasiocampidae, and is probably targeted against insectivorous birds and small reptiles.

A much more dangerous chemical defence system is found in the caterpillars of Lonomia obliqua, which can be found clustered in groups of up to 100 on tree trunks in the Amazon rainforest. There have been numerous incidents where people have unwittingly touched or rubbed their arm against these caterpillars.

The effects of a dose from multiple caterpillars can be very severe, including massive intercranial haemorrhaging and kidney failure. Lonomia obliqua caterpillars are a frequent cause of death in southern Brazil – 354 people died between 1989 and 2005. The fatality rate is about 1.7% – roughly equivalent to that of rattlesnake bites.

Reflex bleeding

The caterpillars of several butterflies including the Large White Pieris brassicae will reflex-bleed if alarmed, and exude toxins from their mouthparts. These fluids are sufficiently noxious to dissuade insectivorous birds, which invariably drop them and then frantically wipe their beaks to remove any trace of the toxins.

A similar form of defence is used by Pericopiine moths in South America, which exude a hemolymph foam from their mouths and spiracles if gripped. Any bird attempting to grip the moth in its beak will experience a very unpleasant taste, and will instantly drop the moth, allowing it to escape.

Hibernation

Hibernation is a process that depresses metabolism and energy consumption during the cold winter months. It ensures that energy is not wasted on fruitless searches for nectar and foliage in winter, and synchronises the spring reawakening with the time when flowers and fresh foliage reappear.

In temperate regions of the world most butterfly species overwinter as larvae. Others hibernate as eggs or pupae. A small number, including Inachis io, Polygonia c-album and Gonepteryx rhamni overwinter instead as adult butterflies. 

To successfully overwinter they need to find a place to hide where they are protected from the worst of the wind, rain and snow. They may be in diapause for several months, and throughout this period they must remain undetected by birds.

Accordingly they have evolved cryptic colours, patterns and unusual wing shapes that combine to provide them with effective camouflage. The Brimstone Gonepteryx rhamni for example hibernates under bramble or ivy leaves and has wings coloured to match winter foliage. Its wings are also leaf-like in shape and have raised venation to simulate the veins of real leaves.

Gonepteryx rhamni hibernating beneath a bramble leaf, West Sussex, England – Adrian Hoskins

Many overwintering species such as the Peacock Inachis io, Camberwell Beauty Nymphalis antiopa and Large Tortoiseshell Nymphalis polychloros hibernate beneath logs or in hollow tree trunks; or in other dark places such as caves or animal burrows. These species have evolved very dark ventral wing patterns which make it difficult for foraging birds to locate them in their gloomy surroundings.

A few species such as the Comma Polygonia c-album hibernate openly, hanging from tree branches or amongst piles of leaf litter on the forest floor. Their dark marbled patterns and strange angular wing shape provides them with an extremely effective dead-leaf disguise.

Polygonia c-album, hibernating beneath a branch, West Sussex, England – Adrian Hoskins

The Red Admiral Vanessa atalanta is a species that doesn’t hibernate in the true sense of the word. On cold wet winter days it hangs motionless from branches, but awakens whenever the weather is warm enough for activity. It can often be seen basking on tree trunks on sunny mid-winter days.

The butterfly gets sustenance from winter berries, tree sap, dung and mineralised moisture on the ground. It continues to breed throughout the winter months, laying eggs on Urtica stinging nettles. In harsh winters the resulting caterpillars perish, but in milder winters a few manage to survive and pupate, producing newly emerged adults in February or early March.

Red Admiral Vanessa atalanta on pine trunk in mid-winter, West Sussex, England – Adrian Hoskins

Another species which overwinters in a state of semi-hibernation is the Monarch Danaus plexippus which gathers in tens of millions each winter, cloaking the trunks of pine trees in the mountains of Mexico. Monarchs are not protected by the “anti-freeze” that prevent the true hibernating species from freezing solid.

They stay alive by periodically shivering their wings, thereby generating heat by friction. Often the butterflies are dislodged from the tree trunks by winds or foraging birds and fall to the ground. Upon landing they are too cold and weak to move so they shiver their wings just sufficiently to raise their temperature enough to enable them to crawl or fly back up onto the tree.

Aestivation

Butterflies need to maintain their body temperatures within operational limits. They quickly become dehydrated if conditions become too hot. Consequently they cool themselves by seeking shade or by drinking water from puddles or the edges of streams. There are times however when even these measures are insufficient to prevent desiccation.

In many tropical regions such as India, Australia, east Africa and Amazonia the dry season can be extremely hot and dry, making it impossible for butterflies to go about their normal activities. Their nectar sources and larval foodplants shrivel and die. Sources of moisture become very scarce. To avoid death in such circumstances butterflies have only two choices. They must either migrate or they must go into a state of diapause. Summer diapause is known as aestivation.

Butterflies in the families Pieridae, Papilionidae and Hesperiidae normally escape the ravages of the dry season by migrating to lusher environments. Members of the Nymphalidae, especially the tribes Ithomiini, Heliconiini, Brassolini, Danaini and Satyrini usually stay put however and seek moist dark places where they can hide away during the arid mid-summer months.

Some South American species e.g. Marpesia berania roost communally in densely packed clusters of 60 or more adults, hanging from branches. Others including Danaus misippus and Euploea core from south-east Asia, and various Heliconius species in South America, congregate in loose groups of between 6-30, hanging from dry twigs.

Ithomiines such as Methona, Melinaea and Mechanitis tend to aggregate at dried out river beds in deeply shaded areas within the forest where they hide away amidst tangles of palm rootlets. They periodically awake from their slumber to imbibe organic fluids from nearby plants, which help them to replenish their dwindling lipids. Mostly however they remain hidden within their rootlet shelters, until such time as the first rains of the wet season stimulate them to seek mates and reproduce.