A butterfly is an insect of the order
Lepidoptera. Like all Lepidoptera, butterflies are notable for their unusual
life cycle with a larval caterpillar stage, an inactive pupal stage, and a spectacular
metamorphosis into a familiar and colourful winged adult form. Most
species are day-flying so they regularly attract attention. The diverse patterns formed by their brightly coloured wings and
their erratic yet graceful flight have made butterfly watching a popular hobby.
Butterflies comprise of the true butterflies (superfamily Papilionoidea), the
skippers (Superfamily Hesperioidea) and the moth-butterflies
(Superfamily Hedyloidea). Butterflies exhibit polymorphism, mimicry and aposematism. Some are known to migrate over large distances. Some butterflies have evolved symbiotic and
parasitic relationships with social insects such as ants. Economically, butterflies are important by virtue of their being one of
the major agents of pollination, in addition to a number of species which are pests on domestic crops and trees.
Culturally, butterflies are a popular motif in the visual and literary arts.
Origin and distribution
Butterflies are nested within the evolutionary tree of moths. Their origins may date back
to the Cretaceous Period, ending 65 million years ago.[1] Unfortunately, the fossil record is very limited. The oldest known fossil is an
unnamed possible skipper butterfly from the Upper Palaeocene (around 57 million year old) of Fur, Denmark [2]. One of the most beautifully preserved is a Metalmark butterfly
(Voltinia dramba) from 25 million year old Dominican amber[3].
Butterflies are today distributed throughout the world except in the very cold and arid regions. There are an estimated 17,500
species of butterflies (Papilionoidea) out of about 180,000 species of Lepidoptera.[4]
Classification
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Phylogeny of the group.[5]
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Presently butterflies are classified in three superfamilies, Hedyloidea, consisting of the
'American moth-butterflies', Hesperioidea, consisting of the 'skippers' and
Papilionoidea or 'true butterflies'. The last two superfamilies are probably
sister taxa, so the butterflies collectively are thought to constitute a natural group or
clade.
The scope of the term butterfly depends on how far the concept is extended. Currently, most experts include the
superfamilies Hedyloidea (the American
moth-butterflies), Hesperioidea (the skippers) and Papilionoidea (the so-called 'true' butterflies). This concept of butterflies including the Hedyloidea is
a recently expanded one, but it makes the group a natural clade, the Rhopalocera.[6]
Butterfly families
The five families of true butterflies usually recognized in the Papilionoidea are:-
The superfamily Hesperioidea comprises one family only, albeit a large one, the
skippers of family Hesperiidae, whereas the superfamily Hedyloidea also consists of a single family Hedylidae with about 40
species.[7]
Taxonomic issues
A study combining morphological and molecular data concluded that Hesperiidae, Papilionidae, Pieridae, Lycaenidae and
Riodinidae could all be strongly supported as monophyletic groups, but the monophyletic status
of Nymphalidae is uncertain. Lycaenidae and Riodinidae were confirmed as sister taxa, and
Papilionidae as the outgroup to the rest of the true butterflies, but the location of Pieridae within the pattern of descent was
unclear, with different lines of evidence suggesting different conclusions. The data suggested that the Hedyloidea are indeed
more closely related to the butterflies than to other moths.[8]
Some older classifications recognize additional families, for example Danaidae, Heliconiidae, Libytheidae and Satyridae, but modern classifications treat these as subfamilies within the
Nymphalidae.
Butterflies and moths
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The dichotomous classification of lepidopterans into butterflies and moths is one that is popular but not used in taxonomy.
The folk groups of butterflies and moths can be distinguished using several features but there are exceptions to most of these
rules.
The four stages in the lifecycle of a butterfly
Mating Common Buckeye Butterflies
Unlike many insects, butterflies do not experience a nymph period, but instead go
through a pupal stage which lies between the larva and the adult stage (the imago).
Butterflies are termed as holometabolous insects, and go through complete
metamorphosis.
It is a popular belief that butterflies have very short life spans. However, butterflies in their adult stage can live from a
week to nearly a year depending on the species. Many species have long larval life stages while others can remain
dormant in their pupal or egg stages and thereby survive winters.[9]
Butterflies may have one or more broods per year. The number of generations per year varies from temperate to tropical regions
with tropical regions showing a trend towards multivoltinism.
Egg
Butterfly eggs consist of a hard-ridged outer layer of shell, called the chorion. This is lined with a thin coating of
wax which prevents the egg from drying out before the larva has had time to fully develop. Each egg contains a number of tiny
funnel-shaped openings at one end, called micropyles; the purpose of these holes is to allow sperm to enter and fertilize
the egg. Butterfly and moth eggs vary greatly in size between species, but they are all either spherical or ovate.
Butterfly eggs are fixed to a leaf with a special glue which hardens rapidly. As it hardens it contracts, deforming the shape
of the egg. This glue is easily seen surrounding the base of every egg forming a meniscus. The nature of the glue is unknown and
is a suitable subject for research. The same glue is produced by a pupa to secure the setae of the cremaster. This glue is so
hard that the silk pad, to which the setae are glued, cannot be separated.
Eggs are usually laid on plants. Each species of butterfly has its own hostplant range and while some species of butterfly are
restricted to just one species of plant, others use a range of plant species, often including members of a common family.
The egg stage lasts a few weeks in most butterflies but eggs laid close to winter, especially in temperate regions, go through
a diapause stage, and the hatching may take place only in spring. Other butterflies may lay their eggs in the spring and
have them hatch in the summer. These butterflies are usually northernly species (Mourning cloak, Tortoiseshells)
Caterpillars
Larvae, or caterpillars, are multi-legged eating machines. They consume
plant leaves and spend practically all of their time in search of
food. Although most caterpillars are herbivorous, a few species such as Spalgis
epius and Liphyra brassolis are entomophagous (insect eating). Some larvae, especially those of the Lycaenidae form mutual associations with ants. They communicate with the
ants using vibrations that are transmitted through the substrate as well as using chemical signals.[10][11] The
ants provide some degree of protection to these larvae and they in turn gather honeydew
secretions.
Caterpillars mature through a series of stages, called instars. Near the end of each instar, the larva undergoes a process
called apolysis, in which the cuticle, a mixture of
chitin and specialized proteins, is released from the
epidermis and the epidermis begins to
form a new cuticle beneath. At the end of each instar, the larva moults the old cuticle, and the new cuticle rapidly hardens and pigments. Development of butterfly wing patterns begins by the last larval
instar.
Butterfly caterpillars have three pairs of true legs from the thoracic segments and up to 6 pairs of prolegs arising from the abdominal segments. These prolegs have rings of tiny hooks called crochets that help
them grip the substrate.
Some caterpillars have the ability to inflate parts of their head to appear snake-like. Many have false eye-spots to enhance
this effect. Some caterpillars have special structures called osmeteria which are everted to
produce smelly chemicals. These are used in defense.
Host plants often have toxic substances in them and caterpillars are able to sequester
these substances and retain them into the adult stage. This helps making them unpalatable to birds and other predators. Such
unpalatibility is advertised using bright red, orange, black or white warning colours. The toxic chemicals in plants are often
evolved specifically to prevent them from being eaten by insects. Insects in turn develop countermeasures or make use of these
toxins for their own survival. This "arms race" has led to the coevolution of insects and their host plants.[12]
Wing development
Close Up Detail of a Butterfly wing
Last instar wing disk,
Junonia coenia
Wings or wing pads are not visible on the outside of the larva, but when larvae are dissected, tiny developing wing
disks can be found on the second and third thoracic segments, in place of the spiracles that are apparent on abdominal
segments. Wing disks develop in association with a trachea that runs along the base of the wing, and are surrounded by a thin
peripodial membrane, which is linked to the outer epidermis of the larva by a tiny duct.
Wing disks are very small until the last larval instar, when they increase dramatically in size, are invaded by branching
tracheae from the wing base that precede the formation of the wing veins, and begin
to develop patterns associated with several landmarks of the wing.
Near pupation, the wings are forced outside the epidermis under pressure from the hemolymph, and although they are initially quite flexible and fragile, by the time the pupa breaks free of the
larval cuticle they have adhered tightly to the outer cuticle of the pupa (in obtect pupae). Within hours, the wings form a
cuticle so hard and well-joined to the body that pupae can be picked up and handled without damage to the wings.
Pupa
When the larva is fully grown, hormones such as prothoracicotropic hormone (PTTH) are
produced. At this point the larva stops feeding and begins "wandering" in the quest of a suitable pupation site, often the
underside of a leaf.
The larva transforms into a pupa (or chrysalis) by anchoring itself to a substrate and moulting
for the last time. The chrysalis is usually incapable of movement, although some species can rapidly move the abdominal segments
or produce sounds to scare potential predators.
The pupal transformation into a butterfly through metamorphosis has
held great appeal to mankind. To transform from the miniature wings visible on the outside of the pupa into large structures
usable for flight, the pupal wings undergo rapid mitosis and absorb a great deal of nutrients. If one wing is surgically removed
early on, the other three will grow to a larger size. In the pupa, the wing forms a structure that becomes compressed from top to
bottom and pleated from proximal to distal ends as it grows, so that it can rapidly be unfolded to its full adult size. Several
boundaries seen in the adult color pattern are marked by changes in the expression of particular transcription factors in the
early pupa.
Adult or Imago
The adult, sexually mature, stage of the insect is known as the imago. As Lepidoptera,
butterflies have four wings that are covered with tiny scales (see photo). The fore and hindwings are not hooked together,
permitting a more graceful flight. An adult butterfly has six legs, but in the nymphalids, the first pair is reduced. After it
emerges from its pupal stage, a butterfly cannot fly until the wings are unfolded. A newly-emerged butterfly needs to spend some
time inflating its wings with blood and letting them dry, during which time it is extremely vulnerable to predators. Some butterflies wings may take up to 3 hours to dry while others take about 1 hour. Most
butterflies and moths will excrete excess dye after hatching. This fluid may be white, red, orange, or in rare cases, blue.
External morphology
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Morphology of a butterfly
Scales
Scales on the wing give the colours
Butterflies are characterized by their scale covered wings. The coloration of butterfly wings is created by minute scales.
These scales are pigmented with melanins that give them blacks and browns, but blues, greens, reds and iridescence are usually
created not by pigments but the microstructure of the scales. This structural coloration is the result of coherent scattering of
light by the photonic crystal nature of the scales.[13][14][15]
Polymorphism
Many adult butterflies exhibit polymorphism, showing differences in appearance. These variations include geographic variants
and seasonal forms. In addition many species have females in multiple forms, often with mimetic forms. Sexual dimorphism in
coloration and appearance is widespread in butterflies. In addition many species show sexual
dimorphism in the patterns of ultraviolet reflectivity, while otherwise appearing identical to the unaided human eye. Most
of the butterflies have a sex-determination system that is represented as
ZW with females being the heterogametic sex (ZW) and males homogametic
(ZZ).[16]
Genetic abnormalities such as gynandromorphy also occur from time to time. In addition
many butterflies are infected by Wolbachia and infection by the bacteria can lead to
the conversion of males into females[17] or the selective
killing of males in the egg stage.[18]
Mimicry
![The Heliconius butterflies from the tropics of the Western Hemisphere are the classical model for Müllerian mimicry.[19]](http://content.answers.com/main/content/wp/en-commons/thumb/e/e1/180px-Heliconius_mimicry.png)
The
Heliconius butterflies from the tropics of the Western Hemisphere are the classical model
for Müllerian mimicry.
[19]
Batesian and Mullerian mimicry in butterflies is common.
Batesian mimics imitate other species to enjoy the protection of an attribute they do not share, aposematism in this case. The Common Mormon of India has female
morphs which imitate the unpalatable red-bodied swallowtails, the Common Rose
and the Crimson Rose. Mullerian mimicry occurs when aposematic species evolve to
resemble each other, presumably to reduce predator sampling rates, the Heliconius butterflies
of the Americas being a good example.
Wing markings called eyespots are present in some species; these may have an
automimicry role for some species. In others, the function may be intraspecies communication,
such as mate attraction. In several cases, however, the function of butterfly eyespots is not clear, and may be an evolutionary
anomaly related to the relative elasticity of the genes that encode the spots.[20][21]
Seasonal polyphenism
Many of the tropical butterflies have distinctive seasonal forms. This phenomenon is termed seasonal polyphenism and
the seasonal forms of the butterflies are called the dry-season and wet-season forms. How the season affects the genetic
expression of patterns is still a subject of research.[22] Experimental modification by ecdysone hormone treatment has demonstrated that it is possible to
control the continuum of expression of variation between the wet and dry-season forms.[23] The dry-season forms are usually more cryptic and it has been suggested that
the protection offered may be an adaptation. Some also show greater dark colours in the wet-season form which may have
thermoregulatory advantages by increasing ability to absorb solar radiation.[24]
Habits
Butterflies feed primarily on nectar from flowers. Some also derive nourishment from
pollen, tree sap, rotting fruit, dung, and dissolved minerals in wet sand or dirt. Butterflies
play an important ecological role as pollinators.
As adults, butterflies consume only liquids and these are sucked by means of their proboscis. They feed on nectar from flowers and also sip water from damp patches. This they do for water, for energy from sugars in
nectar and for sodium and other minerals which are vital for their reproduction. Several species of butterflies need more
sodium than provided by nectar. They are attracted to
sodium in salt and they sometimes land on people, attracted by human sweat. Besides damp patches,
some butterflies also visit dung, rotting fruit or carcasses to obtain minerals and nutrients. In many species, this
Mud-puddling behaviour is restricted to the males and studies have suggested that the
nutrients collected are provided as a nuptial gift along with the spermatophore during mating.[25]
Butterflies sense the air for scents, wind and nectar using their antennae. The antennae come in various shapes and colours.
The hesperids have a pointed angle or hook to the antennae, while most other families show knobbed antennae. The antennae are
richly covered with sensillae. A butterfly's sense of taste is coordinated by chemoreceptors on
the tarsi, which work only on contact, and are used to determine whether an egg-laying insect's offspring will be able to feed on
a leaf before eggs are laid on it[26]. Many butterflies
use chemical signals, pheromones, and specialized scent scales (androconia) and other
structures (coremata or 'Hair pencils' in the Danaidae) are developed in some species.
Antennae shape in the lepidoptera from C. T. Bingham (1905)
Vision is well developed in butterflies and most species are sensitive to the ultraviolet spectrum. Many species show sexual
dimorphism in the patterns of UV reflective patches.[27]
Color vision may be widespread but has been demonstrated in only a few species.[28][29]
Some butterflies have organs of hearing and some species are also known to make stridulatory and clicking sounds.[30]
Many butterflies, such as the Monarch butterfly, are migratory and capable of long distance flights. They migrate during the day and use the sun to orient
themselves. They also perceive polarized light and use it for orientation when the sun is hidden.[31]
Many species of butterfly maintain territories and actively chase other species or individuals that may stray into them. Some
species will bask or perch on chosen perches. The flight styles of butterflies are often characteristic and some species have
courtship flight displays. Basking is an activity which is more common in the cooler hours of the morning. Many species will
orient themselves to gather heat from the sun. Some species have evolved dark wingbases to help in gathering more heat and this
is especially evident in alpine forms.[32]
Flight
Like many other members of the insect world, the lift generated by butterflies is more than
what can be accounted for by steady-state, non-transitory aerodynamics. Studies using
Vanessa atalanta in a windtunnel show that they use a wide variety of
aerodynamic mechanisms to generate force. These include wake capture, vortices at the wing edge, rotational mechanisms and
Weis-Fogh 'clap-and-fling' mechanisms. The butterflies were also able to change from one mode to another rapidly.[33] (See also Insect
flight)
Migration
- See also Insect migration
Many butterflies migrate over long distances. Particularly famous migrations being those of the Monarch butterfly from Mexico to North
America, a distance of about 4,000 to 4,800 kilometres (2500-3000 miles). Other well known migratory species include the
Painted Lady and several of the Danaine
butterflies. Spectacular and large scale migrations associated with the Monsoons are seen in
peninsular India.[34]
Migrations have been studied in more recent times using wing tags and also using stable hydrogen isotopes.[35][36]
Butterflies have been shown to navigate using time compensated sun compasses. They can see polarized light and therefore
orient even in cloudy conditions. The polarized light in the region close to the ultraviolet spectrum is suggested to be
particular important.[37]
It is suggested that most migratory butterflies are those that belong to semi-arid areas where breeding seasons are
short.[38] The life-histories of their host plants also
influence the strategies of the butterflies.[39]
Defense
Butterflies are threatened in their early stages by parasitoids and in all stages by
predators, diseases and environmental factors. They protect themselves by a variety of
means.
Chemical defenses are widespread and are often based on chemicals of plant origin. In many cases the plants themselves have
evolved these toxic substances to reduce attack to them. These defense mechanisms are effective only if they are also well
advertised. Many unpalatable butterflies are brightly colored. This has led to unprotected butterflies evolving forms that appear
like the unpalatable butterflies. These mimetic forms are usually restricted to the females.
Eyespots on the hind wing of this butterfly are part of the animal's defense
Cryptic coloration is found in many butterflies. Some like the oakleaf butterfly are remarkable imitations of leaves.[40] As caterpillars, many defend themselves by freezing and
appearing like sticks or branches. Some papilionid caterpillars resemble bird dropping in their early instars. Some caterpillars
have hairs and bristly structures that provide protection while others are gregarious and form dense aggregations. Some species
also form associations with ants and gain their protection (See Myrmecophile).
Behavioural defenses include perching and wing positions to avoid being conspicuous. Some female Nymphalid butterflies are
known to guard their eggs from parasitoid wasps.[41]
Eyespots and tails are found in many lycaenid butterflies and these divert the attention of predators from the more vital head
region. An alternative theory is that these cause ambush predators such as spiders to approach from the wrong end and allow for
early visual detection.[42]
Notable Species
There are between 15,000 and 20,000 species of butterflies worldwide. Some well known species
from around the world include:
In culture
Art
Der Schmetterlingsjäger (The butterfly hunter) by
Carl Spitzweg (1840), a depiction from
the era of butterfly collection.
Artistic depictions of butterflies have been used in many cultures including Egyptian hieroglyphics 3500 years ago.[43] Today, butterflies are widely used in various objects of
art.
Symbolism
According to the “Butterflies” chapter in Kwaidan: Stories
and Studies of Strange Things, by Lafcadio Hearn, a butterfly is seen as the
personification of a person's soul; whether they be living, dying, or already dead. One
Japanese superstition says that if a butterfly enters your guestroom and perches behind the bamboo screen, the person whom you most love is coming to see you. However, large numbers of butterflies are
viewed as bad omens. When Taira no Masakado was secretly preparing for his famous
revolt, there appeared in Kyoto so vast a swarm of butterflies that the people were frightened —
-thinking the apparition to be a portent of coming evil.[44]
The Russian word for butterflies, pronounced "bah' bch ka", it also means "bow tie". It is a diminutive of "baba" or "babka"
(= "woman, grandmother, cake", whence also "babushka" = "grandmother" in English, "babushka" = "a grandma-style headkerchief")
and in Greek it means soul.[45] According to
Mircea Eliade's Encyclopedia of Religion, some of the Nagas of Manipur trace their ancestry from a butterfly.[46]
In Chinese culture two butterflies flying together are a symbol of love. Also a
famous Chinese folk story called Butterfly Lovers. The Taoist philosopher Zhuangzi once had a dream of being a butterfly flying
without care about humanity, however when he woke up and realised it was just a dream, he thought to himself "Was I before a man
who dreamt about being a butterfly, or am I now a butterfly who dreams about being a man?"
In some old cultures, butterflies also symbolize rebirth into a new life after being inside a
cocoon for a period of time.
Some people say that when a butterfly lands on you it means good luck. The idiom "butterflies in the stomach" is used to describe a state of nervousness.
Technological inspiration
Studies on the reflection of light by the scales on wings of swallowtail butterflies have to led to the innovation of more
efficient Light-emitting diodes.[47]
The structural colouration of butterflies is inspiring nanotechnology research to produce paints that do not use toxic
pigments and in the development of new display technologies.[48]
Gallery
Family Papilionidae- The Swallowtails
Green Swallowtail (Papilio blumei), Metro Toronto Zoo
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Family Pieridae - The Whites and Yellows
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Little Yellow,
Pyrisitia lisa.
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Family Riodinidae - The Metalmarks, Punches and Judies
Family Nymphalidae - The Brush-footed Butterflies
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Morpho rhetenor helena a morphine from
South America.
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![The Heliconius butterflies from the tropics of the Western Hemisphere are the classical model for Müllerian mimicry.[19]](http://www.answers.com/main/Record2?a=NR&url=http%3A%2F%2Fcommons.wikimedia.org%2Fwiki%2FImage%3AHeliconius%2520mimicry.png)
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