insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...
moth
Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...
s. Lepidoptera are distinguished from other orders by the presence of
scales
Scale or scales may refer to:
Mathematics
* Scale (descriptive set theory), an object defined on a set of points
* Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original
* Scale factor, a number w ...
on the external parts of the body and appendages, especially the wings. Butterflies and moths vary in size from
microlepidoptera
Microlepidoptera (micromoths) is an artificial (i.e., unranked and not monophyletic) grouping of moth families, commonly known as the 'smaller moths' (micro, Lepidoptera). These generally have wingspans of under 20 mm, and are thus harder to ...
only a few millimetres long, to a wingspan of many inches such as the
Atlas moth
''Attacus atlas'', the Atlas moth, is a large saturniid moth endemic to the forests of Asia. The species was first described by Carl Linnaeus in his 1758 10th edition of ''Systema Naturae''.
Description
The Atlas moth is one of the largest ...
. Comprising over 160,000 described species, the Lepidoptera possess variations of the basic body structure which has evolved to gain advantages in adaptation and distribution.
Lepidopterans undergo
complete metamorphosis
Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago (or adult). Holometabolism is a synapomorphic trait of all insects in the superorder Endopterygo ...
, going through a four-stage
life cycle
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
*Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
* Life-cycle hypothesis ...
:
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
,
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
pupa
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...
sclerotised
Sclerotin is a component of the cuticle of various Arthropoda, most familiarly insects. It is formed by cross-linking members of particular classes of protein molecules, a biochemical process called sclerotization, a form of tanning in which qui ...
) head capsule, chewing mouthparts, and a soft body, that may have hair-like or other projections, three pairs of true legs, and up to five pairs of
proleg
A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the order Lepidoptera, though they can also be found on other larval insects such as sawflies and a few other types of in ...
s. Most caterpillars are herbivores, but a few are
carnivore
A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other s ...
s (some eat ants, aphids, or other caterpillars) or detritivores. Larvae are the feeding and growing stages and periodically undergo hormone-induced ecdysis, developing further with each
instar
An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...
, until they undergo the final larval–pupal moult. The larvae of many lepidopteran species will either make a spun casing of silk called a cocoon and
pupate
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...
inside it, or will pupate in a cell under the ground. In many butterflies, the pupa is suspended from a cremaster and is called a ''chrysalis''.
The adult body has a hardened
exoskeleton
An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...
, except for the abdomen which is less sclerotised. The head is shaped like a capsule with appendages arising from it. Adult mouthparts include a prominent
proboscis
A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
formed from maxillary galeae, and are adapted for sucking nectar. Some species do not feed as adults, and may have reduced mouthparts, while others have them modified for piercing and suck blood or fruit juices.
Mandibles
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
are absent in all except the
Micropterigidae
Micropterigoidea is the superfamily of "mandibulate archaic moths", all placed in the single family Micropterigidae, containing currently about twenty living genera. They are considered the most primitive extant lineage of lepidoptera (Kristense ...
which have chewing mouthparts. (No preview.) Adult Lepidoptera have two immobile, multi-faceted
compound eye
A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which disti ...
s, and only two simple eyes or ocelli, which may be reduced.Scoble (1995). Section "Sensation", (pp. 26–38). The three segments of the
thorax
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...
are fused together. Antennae are prominent and besides the faculty of smell, also aid navigation, orientation, and balance during flight. In moths, males frequently have more feathery antennae than females, for detecting the female
pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
s at a distance. There are two pairs of
membranous
A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. ...
wings
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expre ...
which arise from the mesothoracic (middle) and metathoracic (third) segments; they are usually completely covered by minute
scales
Scale or scales may refer to:
Mathematics
* Scale (descriptive set theory), an object defined on a set of points
* Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original
* Scale factor, a number w ...
. The two wings on each side act as one by virtue of wing-locking mechanisms. In some groups, the females are flightless and have reduced wings. The abdomen has ten segments connected with movable inter-segmental membranes. The last segments of the abdomen form the external
genitalia
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
. The genitalia are complex and provide the basis for family identification and species discrimination.
The wings, head parts of thorax, and abdomen of Lepidoptera are covered with minute scales, from which feature the order Lepidoptera derives its names, the word ''lepidos'' in
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
meaning "scale". Most scales are lamellar (blade like) and attached with a pedicel, while other forms may be hair like or specialised as secondary sexual characteristics. The lumen, or surface of the lamella, has a complex structure. It gives colour either due to the
pigment
A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...
s contained within it or through its three-dimensional structure.Scoble (1995). Section "Scales", (pp. 63–66). Scales provide a number of functions, which include
insulation
Insulation may refer to:
Thermal
* Thermal insulation, use of materials to reduce rates of heat transfer
** List of insulation materials
** Building insulation, thermal insulation added to buildings for comfort and energy efficiency
*** Insulated ...
,
thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
, and aiding flight, amongst others, the most important of which is the large diversity of vivid or indistinct patterns they provide which help the organism protect itself by
camouflage
Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
Holometabola
Endopterygota (from Ancient Greek ''endon'' 'inner' + ''pterón'' 'wing' + New Latin ''-ota'' 'having'), also known as Holometabola, is a superorder of insects within the infraclass Neoptera that go through distinctive larval, pupal, and adult st ...
, Lepidoptera undergo complete metamorphosis, going through a four-stage life cycle: egg, larva / caterpillar, pupa / chrysalis, and imago (plural: ''imagines'') / adult.
Lepidopterans range in size from a few millimetres in length, such as in the case of microlepidoptera, to a wingspan of many inches, such as the
Atlas moth
''Attacus atlas'', the Atlas moth, is a large saturniid moth endemic to the forests of Asia. The species was first described by Carl Linnaeus in his 1758 10th edition of ''Systema Naturae''.
Description
The Atlas moth is one of the largest ...
and the world's largest butterfly
Queen Alexandra's birdwing
''Ornithoptera alexandrae'', the Queen Alexandra's birdwing, is the largest species of butterfly in the world, with females reaching wingspans slightly in excess of 25 cm to 28 cm (9.8 inches to 11 inches). This birdwing is restricted to the ...
.
General body plan
The body of an adult butterfly or moth (the imago) has three distinct divisions, called tagmata, connected at constrictions; these tagmata are the head, thorax, and abdomen. Adult lepidopterans have four wings — a forewing and a hindwing on both the left and the right side of the thorax — and, like all insects, three pairs of legs.
The morphological characteristics which distinguish the order Lepidoptera from other insect orders are:
* ''Head'': The head has large compound eyes and, if mouthparts are present, they are almost always a drinking straw-like proboscis.
* ''Scales'': Scales cover the external surface of the body and appendages.
* ''Thorax'': The
prothorax
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum ( ventral), and the propleuron ( lateral) o ...
is usually reduced.
* ''Wings'': Two pairs of wings are present in almost all taxa. The wings have very few cross veins.
* ''Abdomen'': The posterior abdominal segments are extensively modified for reproduction. Cerci are absent.
* ''Larva'': Lepidoptera larvae are known as caterpillars, and have a well-developed head and mandibles. They can have from zero to five pairs of
proleg
A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the order Lepidoptera, though they can also be found on other larval insects such as sawflies and a few other types of in ...
s, usually four.
* ''Pupa'': The pupae in most species are adecticous (with no functional mandibles in the pupal state) and obtect (with appendages fused or glued to the body), while others are decticous (with functional mandibles present in the pupal state) and exarate (having the antennae, legs, and wings free).
Distinguishing taxonomic features
The chief characteristics used to classify lepidopteran species, genera, and families are:
* the mouthparts
* the shape and venation of the wings
** whether the wings are homoneurous (the venation of the forewings and hindwings alike) or heteroneurous (forewings and hindwings different)
** whether the wings are aculeate (more or less covered with specialized bristles called microsetae) or nonaculeate
** the type of wing coupling (jugate or frenate)
* the anatomy of the reproductive organs
* the structure of larva and position of primary setae
* whether the pupa is exarate or obtect
The morphological characteristics of caterpillars and pupae used for classification are completely different from that of adults; different classification schemes are sometimes provided separately for classifying adults, larvae, and pupae. The characteristics of immature stages are increasingly used for taxonomic purposes as they provide insights into systematics and phylogenies of Lepidoptera that are not apparent from examination of adults.
Head
Like all animal heads, the head of a butterfly or moth contains the feeding organs and the major sense organs. The head typically consists of two antennae, two compound eyes, two
palpi
Pedipalps (commonly shortened to palps or palpi) are the second pair of appendages of chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to the chelicerae ("jaws") and ...
, and a proboscis. Lepidoptera have
ocelli
A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...
which may or may not be visible. They also have sensory structures called ''chaetosemata'', the functions of which are largely unknown. The head is filled largely by the brain, the sucking pump, and its associated muscle bundles. Unlike the adults, the
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
e have one-segmented mandibles.Scoble (1995). Section "The Adult Head – Feeding and Sensation", (pp. 4–22).
The head capsule is well sclerotised and has a number of ''sclerites'' or plates, separated by ''sutures''. The sclerites are difficult to distinguish from ''sulci'' (singular – '' sulcus'') which are secondary thickenings. The regions of the head have been divided into a number of areas which act as a topographical guide for description by lepidopterists but cannot be discriminated in terms of their development. The head is covered by hair-like or lamellar scales and found either as tufts on the ''frons'' or ''vertex'' (referred to as ''rough-scaled'') or pressed close to the head (referred to as ''smooth-scaled'').
The sensory organs and structures on the head show great variety, and the shape and form of these structures, as also their presence or absence, are important taxonomic indicators for classifying taxa into families.
File:Insect SEM gracilariidae.jpg, Head of a moth of family
Gracillariidae
Gracillariidae is an important family of insects in the order Lepidoptera and the principal family of leaf miners that includes several economic, horticultural or recently invasive pest species such as the horse-chestnut leaf miner, ''Camerar ...
showing extent of scales on the head
File:Rough-scaled_Lepidoptera_head.jpg, Rough-scaled head of moth ''
Monopis icterogastra
''Monopis icterogastra'', the wool moth, is a moth of the family Tineidae. It is found in most of Australia
Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continen ...
'' (family
Tineidae
Tineidae is a family of moths in the order Lepidoptera described by Pierre André Latreille in 1810. Collectively, they are known as fungus moths or tineid moths. The family contains considerably more than 3,000 species in more than 300 genera. ...
Gelechiidae
The Gelechiidae are a family of moths commonly referred to as twirler moths or gelechiid moths. They are the namesake family of the huge and little-studied superfamily Gelechioidea, and the family's taxonomy has been subject to considerable d ...
)
Antennae
Antennae are prominent paired appendages that project forwards between the animal's eyes and consist of a number of segments. In the case of butterflies, their length varies from half the length of the forewing to three-quarters of the length of the forewing. The antennae of butterflies are either slender and knobbed at the tip and, in the case of the Hesperiidae, are hooked at the tip. In some butterfly genera such as ''
Libythea
''Libythea'' is a widespread genus of nymphalid butterflies
Butterflies are insects in the macrolepidopteran clade Rhopalocera from the order Lepidoptera, which also includes moths. Adult butterflies have large, often brightly coloured ...
'' and '' Taractrothera'' the knob is hollowed underneath. Moth antennae are either ''filiform'' (thread like), ''unipectinate'' (comb like), ''bipectinate'' (feather like), hooked, clubbed, or thickened. ''
Bombyx mandarina
''Bombyx mandarina'', the wild silk moth, is an insect from the moth family Bombycidae. It is the closest relative of '' Bombyx mori'', the domesticated silk moth. The silkworm is the larva or caterpillar of a silk moth. Unlike the domesticated ...
'' is an example with bipectinate antennae. Some moths have knobbed antennae akin to those of butterflies, such as the family Castniidae.
Antennae are the primary organs of olfaction (smell) in Lepidoptera. The antenna surface is covered with large numbers of olfactory scales, hairs, or pits; as many as 1,370,000 are found on the antennae of a
monarch
A monarch is a head of stateWebster's II New College DictionarMonarch Houghton Mifflin. Boston. 2001. p. 707. for life or until abdication, and therefore the head of state of a monarchy. A monarch may exercise the highest authority and power i ...
. Antennae are extremely sensitive; the feathered antennae of male moths from the Saturniidae, Lasiocampidae, and many other families are so sensitive that they can detect the pheromones of female moths from distances of up to away. Lepidoptera antennae can be angled in many positions. They help the insect in locating the scent and can be considered to act as a kind of "olfactory radar". In moths, males frequently have antennae which are more feathery than those of the females, for detecting the female pheromones at a distance. Since females do not need to detect the males, they have simpler antennae. Antennae have also been found to play a role in the time-compensated sun compass orientation in migratory monarch butterflies.
File:Eriocrania_cicatricella_cropped.jpg,
File:Abantiades_barcas_cropped.jpg,
File:Actias_artemis_cropped.jpg,
File:Silver-spotted_Skipper%2C_Megan_McCarty58_cropped.jpg,
File:Vanessa_February_2008-1.jpg,
File:Deleiphila_elpenor_003_cropped.JPG,
File:CastniidaeMexico.JPG,
File:Nemophora_degeerella-01_(xndr).jpg,
Eyes
Lepidoptera have two large, immovable compound eyes which consist of a large number of
facet
Facets () are flat faces on geometric shapes. The organization of naturally occurring facets was key to early developments in crystallography, since they reflect the underlying symmetry of the crystal structure. Gemstones commonly have facets cut ...
s or lenses, each connected to a lens-like cylinder which is attached to a nerve leading to the
brain
A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a ve ...
. Each eye may have up to 17,000 individual light receptors (
ommatidia
The compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia (singular: ommatidium). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The ...
) which in combination provide a broad mosaic view of the surrounding area. One tropical Asian family, the Amphitheridae, has compound eyes divided into two distinct segments. The eyes are usually smooth but may be covered by minute hairs. The eyes of butterflies are usually brown, golden brown, or even red as in the case of some species of skippers.
While most insects have three simple eyes, or
ocelli
A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...
, only two ocelli are present in all species of Lepidoptera, except a few moths, one on each side of the head near the edge of the compound eye. On some species, sense organs called
chaetosemata
This glossary of entomology describes terms used in the formal study of insect species by entomologists.
A–C
A synthetic chlorinated hydrocarbon insecticide, toxic to vertebrates. Though i ...
are found near the ocelli. The ocelli are not homologous to the simple eyes of caterpillars which are differently named as
stemmata
A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...
. The ocelli of Lepidoptera are reduced externally in some families; where present, they are unfocussed, unlike stemmata of larvae which are fully focussed. The utility of ocelli is not understood at present.
Butterflies and moths are able to see
ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
(UV) light, and wing colours and patterns are principally observed by Lepidoptera in these wavelengths of light. The patterns seen on their wing under UV light differ considerably from those seen in normal light. The UV patterns act as visual cues which help differentiate between species for the purpose of mating. Studies have been carried out on Lepidoptera (mostly butterflies) wing patterns illuminated by UV light.
Palpi
Typically, the labial palpi are prominent, three-segmented, springing from under the head and curving up in front of the face. There is great variation in morphology of labial palpi in different families of Lepidoptera; sometimes the palpi are separate and sometimes they are ''connivent'' and form a beak, but they are always independently movable. In other cases, the labial palpi may not be erect but ''porrect'' (projecting forward horizontally). Palpi consist of a short basal segment, a comparatively long central segment, and a narrow terminal portion. The first two segments are densely scaled and may be
hirsute
Hirsutism is excessive body hair on parts of the body where hair is normally absent or minimal. The word is from early 17th century: from Latin ''hirsutus'' meaning "hairy". It usually refers to a "male" pattern of hair growth in a female that ...
; the terminal segment is bare. The terminal segment may be blunt or pointed; it may project straight or at an angle from the second segment inside which it may be concealed.
Mouthparts
While mandibles or jaws (chewing mouthparts) are only present in the caterpillar stage, the mouthparts of most adult Lepidoptera mainly consist of the sucking kind; this part is known as the proboscis or ''haustellum''. A few Lepidoptera species have reduced mouthparts and do not feed in the adult state. Others, such as the basal family Micropterigidae, have chewing mouthparts.
The proboscis (plural –
proboscis
A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
es) is formed from maxillary galeae and is adapted for sucking nectar. It consists of two tubes held together by hooks and separable for cleaning. Each tube is inwardly concave, thus forming a central tube up which moisture is sucked. Suction is effected through the contraction and expansion of a sac in the head. The proboscis is coiled under the head when the insect is at rest and extended only when feeding. The maxillary palpi are reduced and even vestigial. They are conspicuous and five segmented in some of the more basal families and are often folded.
The shape and dimensions of the proboscis have evolved to give different species a wider and therefore more advantageous diet. There is an
allometric
Allometry is the study of the relationship of body size to shape, anatomy, physiology and finally behaviour, first outlined by Otto Snell in 1892, by D'Arcy Thompson in 1917 in ''On Growth and Form'' and by Julian Huxley in 1932.
Overview
Allome ...
scaling relationship between body mass of Lepidoptera and length of proboscis from which an interesting adaptive departure is the unusually long-tongued sphinx moth ''
Xanthopan morganii praedicta
''Xanthopan'' is a monotypic genus of sphinx moth, with ''Xanthopan morganii'' (often misspelled as "''morgani''"), commonly called Morgan's sphinx moth, as its sole species. It is a very large sphinx moth from Southern Africa (Zimbabwe, Zambia, ...
''.
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
predicted the existence and proboscis length of this moth before its discovery based on his knowledge of the long-spurred Madagascan star orchid ''
Angraecum sesquipedale
''Angraecum sesquipedale'' , also known as Darwin's orchid, Christmas orchid, Star of Bethlehem orchid, and king of the angraecums, is an epiphytic orchid in the genus ''Angraecum'' endemic to Madagascar. The orchid was first discovered by the Fre ...
''.
There are primarily two feeding guilds in Lepidoptera – the nectarivorous who obtain the majority of their nutritional requirements from floral nectar and those of the frugivorous guild who feed primarily on juices of rotting fruit or fermenting tree sap. There are substantial differences between the morphology of the proboscises of both feeding guilds. Hawkmoths (family
Sphingidae
The Sphingidae are a family of moths (Lepidoptera) called sphinx moths, also colloquially known as hawk moths, with many of their caterpillars known as “hornworms”; it includes about 1,450 species. It is best represented in the tropics, but ...
) have elongated proboscises which enable them to feed on and pollinate flowers with long tubular corollas. Besides this, a number of taxa (especially
noctuid
The Noctuidae, commonly known as owlet moths, cutworms or armyworms, are a family of moths. They are considered the most controversial family in the superfamily Noctuoidea because many of the clades are constantly changing, along with the other f ...
moths) have evolved different proboscis morphologies. Certain noctuid species have developed piercing mouthparts; the proboscis has sclerotised scales on the tip with which to pierce and suck blood or fruit juices. Proboscises in some ''
Heliconius
''Heliconius'' comprises a colorful and widespread genus of brush-footed butterflies commonly known as the longwings or heliconians. This genus is distributed throughout the tropical and subtropical regions of the New World, from South America ...
'' species have evolved to consume solids such as pollen. Some other moths, mostly noctuids, have modified proboscises to suit their mode of nutrition – lachrymophagy (feeding on tears of sleeping birds). The proboscises often have sharp apices as well as a host of barbs and spurs on the stem.
File:Butterfly tongue.jpg, Scanning electron micrograph of the proboscis of a moth from family
Pyralidae
The Pyralidae, commonly called pyralid moths, snout moths or grass moths, are a family of Lepidoptera in the ditrysian superfamily Pyraloidea. In many (particularly older) classifications, the grass moths (Crambidae) are included in the Pyralida ...
File:Siproeta stelenes (Green Malachite) sucking a banana.JPG, A nymphalid butterfly sucking on a banana
File:Heliconius sara-01 (xndr).jpg, Sara longwing ('' Heliconius sara''), one of many ''Heliconius'' species known to feed on pollen, with pollen on its proboscis
File:NHM_Xanthopan_morgani.jpg, ''
Xanthopan morganii
''Xanthopan'' is a monotypic genus of sphinx moth, with ''Xanthopan morganii'' (often misspelled as "''morgani''"), commonly called Morgan's sphinx moth, as its sole species. It is a very large sphinx moth from Southern Africa (Zimbabwe, Zambia, ...
'', an African sphingid, has a foot-long proboscis adapted for feeding from the orchid ''
Angraecum sesquipedale
''Angraecum sesquipedale'' , also known as Darwin's orchid, Christmas orchid, Star of Bethlehem orchid, and king of the angraecums, is an epiphytic orchid in the genus ''Angraecum'' endemic to Madagascar. The orchid was first discovered by the Fre ...
''
File:A_butterfly_feeding_on_the_tears_of_a_turtle_in_Ecuador.jpg, Lachryphagous Lepidoptera, such as the two Julia butterflies (
Dryas iulia
''Dryas iulia'' (often incorrectly spelled ''julia''),Lamas, G. (editor) (2004). Atlas of Neotropical Lepidoptera. Checklist: Part 4A. Hesperioidea – Papilionoidea. commonly called the Julia butterfly, Julia heliconian, the flame, or flambeau ...
) drinking the tears of turtles in Ecuador, have hooks and barbs at the tip of the proboscis
Thorax
The thorax, which develops from segments 2, 3, and 4 of the larva, consists of three invisibly divided segments, namely
prothorax
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum ( ventral), and the propleuron ( lateral) o ...
,
metathorax
The metathorax is the posterior of the three segments in the thorax of an insect, and bears the third pair of legs. Its principal sclerites ( exoskeletal plates) are the metanotum (dorsal), the metasternum (ventral), and the metapleuron (lateral) ...
, and
mesothorax
The mesothorax is the middle of the three segments of the thorax of hexapods, and bears the second pair of legs. Its principal sclerites (exoskeletal plates) are the mesonotum (dorsal), the mesosternum (ventral), and the mesopleuron (lateral) on ...
. The organs of insect locomotion – the legs and wings – are borne on the thorax. The forelegs spring from the prothorax, the forewings and middle pair of legs are borne on the mesothorax, and the hindwings and hindlegs arise from the metathorax. In some cases, the wings are vestigial.Scoble (1995) Chapter 3: "The adult thorax – a study in function & effect" (pp. 39–40).
The upper and lower parts of the thorax (
terga
A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'ma ...
and
sterna
''Sterna'' is a genus of terns in the bird family Laridae. The genus used to encompass most "white" terns indiscriminately, but mtDNA sequence comparisons have recently determined that this arrangement is paraphyletic. It is now restricted to t ...
respectively) are composed of segmental and intrasegmental
sclerite
A sclerite (Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly ...
s which display secondary sclerotisation and considerable modification in the Lepidoptera. The prothorax is the simplest and smallest of the three segments while the mesothorax is the most developed.
Between the head and thorax is the membranous neck or ''cervix''. It comprises a pair of lateral cervical sclerites and is composed of both cephalic and thoracic elements. Between the head and the thorax is a tufted scale called the
pronotum
The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...
. On either side is a shield-like scale called a
scapula
The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...
. In the
Noctuoidea
Noctuoidea is the superfamily of noctuid (Latin "night owl") or "owlet" moths, and has more than 70,000 described species, the largest number of for any Lepidopteran superfamily. Its classification has not yet reached a satisfactory or stable st ...
, the metathorax is modified with a pair of
tympanal organ
A tympanal organ (or tympanic organ) is a hearing organ in insects, consisting of a membrane ( tympanum) stretched across a frame backed by an air sac and associated sensory neurons. Sounds vibrate the membrane, and the vibrations are sensed by ...
s.
Leg
Forelegs in the
Papilionoidea
The superfamily Papilionoidea (from the genus '' Papilio'', meaning "butterfly") contains all the butterflies except for the moth-like Hedyloidea.
The members of the Papilionoidea may be distinguished by the following combination of character ...
exhibit reduction of various forms: the butterfly family
Nymphalidae
The Nymphalidae are the largest family of butterflies, with more than 6,000 species distributed throughout most of the world. Belonging to the superfamily Papilionoidea, they are usually medium-sized to large butterflies. Most species have a red ...
, or brush-footed butterflies as they are commonly known, have only the rear two pairs of legs fully functional with the forward pair strongly reduced and not capable of walking or perching. In the Lycaenidae, the tarsus is unsegmented, as the tarsomeres are fused, and, tarsal claws are absent. The aroliar pad (a pad projecting between the tarsal claws of some insects) and pulvilli (singular: pulvillus, a pad or lobe beneath each tarsal claw) are reduced or absent in the
Papilionidae
Swallowtail butterflies are large, colorful butterflies in the family Papilionidae, and include over 550 species. Though the majority are tropical, members of the family inhabit every continent except Antarctica. The family includes the larg ...
. The tarsal claws are also absent in the
Riodinidae
Riodinidae is the family of metalmark butterflies. The common name "metalmarks" refers to the small, metallic-looking spots commonly found on their wings. The 1532 species are placed in 146 genera. Although mostly Neotropical in distribution, t ...
.
In Lepidoptera, the three pairs of legs are covered with scales. Lepidoptera also have olfactory organs on their feet which aid in "tasting" or "smelling" food plants.
Wings
Adult Lepidoptera have two pairs of membranous wings covered, usually completely, by minute scales. A wing consists of an upper and lower membrane which are connected by minute fibres and strengthened by a system of thickened hollow ribs, popularly but incorrectly referred to as "veins", as they may also contain tracheae, nerve fibres, and blood vessels.. The membranes are covered with minute scales which have jagged ends or hairs and are attached by hooks. The wings are moved by the rapid muscular contraction and expansion of the thorax.
The wings arise from the meso- and meta-thoracic segments and are similar in size in the basal groups. In more derived groups, the meso-thoracic wings are larger with more powerful musculature at their bases and more rigid vein structures on the
costal
Costal may refer to:
* an adjective related to the rib () in anatomy
** Costal cartilage, a type of cartilage forming bars which serve to prolong the ribs forward
** Costal margin, the medial margin formed by the false ribs
** Costal surface (disa ...
edge.
Besides providing the primary function of flight, wings also have secondary functions of
self-defence
Self-defense (self-defence primarily in Commonwealth English) is a countermeasure that involves defending the health and well-being of oneself from harm. The use of the right of self-defense as a legal justification for the use of force in ...
, camouflage and thermoregulation. In some Lepidoptera families such as the
Psychidae
The Psychidae (bagworm moths, also simply bagworms or bagmoths) are a family of the Lepidoptera ( butterflies and moths). The bagworm family is fairly small, with about 1,350 species described. Bagworm species are found globally, with some, ...
and
Lymantriidae
The Lymantriinae (formerly called the Lymantriidae) are a subfamily of moths of the family Erebidae. The taxon was erected by George Hampson in 1893.
Many of its component species are referred to as "tussock moths" of one sort or another. The cat ...
, the wings are reduced or even absent (often in the female but not the male).
Shape
The shape of wings exhibits great variety in Lepidoptera. In the case of the Papilionoidea, the
costa
Costa may refer to:
Biology
* Rib (Latin: ''costa''), in vertebrate anatomy
* Costa (botany), the central strand of a plant leaf or thallus
* Costa (coral), a stony rib, part of the skeleton of a coral
* Costa (entomology), the leading edge of th ...
may be straight or highly arched. It is sometimes
concave
Concave or concavity may refer to:
Science and technology
* Concave lens
* Concave mirror
Mathematics
* Concave function, the negative of a convex function
* Concave polygon, a polygon which is not convex
* Concave set
* The concavity of a ...
on the hindwing. It is occasionally serrate or minutely saw toothed on the forewing. The apex may be rounded, pointed, or
falcate
The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular ...
(produced and concave below). The
termen
Termen is a municipality in the district of Brig in the canton of Valais in Switzerland.
History
Termen is first mentioned in 1201 as ''Terman''.
Geography
Termen has an area, , of . Of this area, 42.2% is used for agricultural purposes, wh ...
tends to be straight or concave on the forewing while it is usually more or less convex on the hindwing. The termen is often crenulate or
dentate
Dentate may refer to:
* A species having dentition
* An energy-dissipating baffle block in a spillway
* An individual not being edentulous
* Dentate gyrus of the hippocampus
* Dentate nucleus of the cerebellum
* Denticity in chemistry
* Dentat ...
, i.e. produced at each vein and concave in between them. The dorsum is normally straight but may be concave.
The hindwing is frequently caudate, i.e. the veins near the end of the tornus have one or more tails. The tornus itself being often produced and frequently lobed. Along the hindwing termen there are tightly-packed scales in a double row. The underside of the scales project and form a regular narrow fringe referred to as cilia.
File:Pterophorus pentadactyla MHNT.jpg, The plume moths (family
Pterophoridae
The Pterophoridae or plume moths are a family of Lepidoptera with unusually modified wings. Though they belong to the Apoditrysia like the larger moths and the butterflies, unlike these they are tiny and were formerly included among the assemblag ...
) have split wings
File:Alucita hexadactyla01.jpg, In the many-plumed moths (family Alucitidae), wings are split along each vein
File:Palumbina_guerinii.jpg, Microlepidoptera of the
Gelechioidea
__NOTOC__
Gelechioidea (from the type genus ''Gelechia
''Gelechia'' is a genus of moths in the family Gelechiidae. The type species is '' Gelechia rhombella''.
Species
*Subgenus ''Gelechia''
**'' Gelechia asinella'' (Hubner, 1796)
**'' Gel ...
, such as ''
Palumbina guerinii
''Palumbina guerinii'' is a moth of the family Gelechiidae. It is found in southern Europe, from the Iberian Peninsula north to France, east to Italy and Greece.
The wingspan
The wingspan (or just span) of a bird or an airplane is the dist ...
'', have hair-like fringes along the hindwings
File:Chrysiridia_Madagascarensis2(Better_Crop).JPG, Tailed hindwings of Madagascan sunset moth (''
Chrysiridia rhipheus
''Chrysiridia rhipheus'', the Madagascan sunset moth, is a species of day-flying moth of the family Uraniidae. It is considered one of the most impressive and appealing-looking lepidopterans. Famous worldwide, it is featured in most coffee tabl ...
'' family
Uraniidae
The Uraniidae are a family of moths containing four subfamilies, 90 genera, and roughly 700 species. The family is distributed throughout the tropics of the Americas, Africa and Indo-Australia.Carter, David, ''Eyewitness Handbook to Butterflies ...
)
File:Monkey_Puzzle_Rathinda_amor_by_kadavoor_edit_by_b%C3%B6hringer.jpg, Lycaenids, such as the monkey puzzle (''
Rathinda amor
''Rathinda'' is a butterfly genus in the family Lycaenidae. It consists of a single species, ''Rathinda amor'', the monkey puzzle, found in Sri Lanka and India.Hyaline patches on the wings of a
hummingbird hawk-moth
The hummingbird hawk-moth (''Macroglossum stellatarum'') is a species of hawk moth found across temperate regions of Eurasia. The species is named for its similarity to hummingbirds, as they feed on the nectar of tube-shaped flowers using thei ...
, the snowberry clearwing (''
Hemaris diffinis
''Hemaris diffinis'', the snowberry clearwing, is a moth of the order Lepidoptera, family Sphingidae. This moth is sometimes called "hummingbird moth" or "flying lobster". This moth should not be confused with the hummingbird hawk-moth of Eur ...
'')
File:Pachyerannis obliquaria1.jpg, '' Pachyerannis obliquaria'', mating pair – winged male above, small wingless female below
Venation
Tubular veins run through the two-layered membranous wing. Veins are connected to the
haemocoel
The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
and in theory allow haemolymph to flow through them. In addition, a nerve and trachea may pass through the veins.
Lepidopteran venation is simple in that there are few crossbars. The wing venation in Lepidoptera is a diagnostic for distinguishing between the taxa as also the genera and families. The terminology is based on the Comstock-Needham system which gives the morphological description of
insect wing
Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax), and the two pairs are often referred to as the forewings and hindw ...
venation.Scoble (1995). Section "Wings". Pg 55. In the basal Lepidoptera, the venation of the forewing is similar to that of the hindwing; a condition referred to as "homoneurous". The
Micropterigidae
Micropterigoidea is the superfamily of "mandibulate archaic moths", all placed in the single family Micropterigidae, containing currently about twenty living genera. They are considered the most primitive extant lineage of lepidoptera (Kristense ...
(Zeugloptera) have venation that resembles the most primitive
caddisflies
The caddisflies, or order Trichoptera, are a group of insects with aquatic larvae and terrestrial adults. There are approximately 14,500 described species, most of which can be divided into the suborders Integripalpia and Annulipalpia on the ...
(Trichoptera). All other Lepidoptera, the vast majority (around 98%), are "heteroneurous", the venation of the hindwing differing from that from the forewing and being sometimes reduced. Moths of the families
Nepticulidae
Nepticulidae is a family of very small moths with a worldwide distribution. They are characterised by eyecaps over the eyes (see also Opostegidae, Bucculatricidae, Lyonetiidae). These pigmy moths or midget moths, as they are commonly known, incl ...
Gracillariidae
Gracillariidae is an important family of insects in the order Lepidoptera and the principal family of leaf miners that includes several economic, horticultural or recently invasive pest species such as the horse-chestnut leaf miner, ''Camerar ...
, Tischeriidae, and Bucculatricidae, amongst others, often have greatly reduced venation in both wings. Homoneurous moths tend to have the "jugum" form of wing coupling as opposed to the "frenulum–retinaculum" arrangement in the case of more advanced families.
File:Comstock-needham.svg, Insect wing venation, showing the names after the Comstock–Needham system
File:Sabatinca_lucilia.jpg, Homoneurous venation in ''
Sabatinca lucilia
''Sabatinca lucilia'' is a species of moth in the family Micropterigidae. It is endemic to New Zealand and is found in the top half of the North Island. The adults of this species are on the wing from the end of November until the beginning of M ...
'' (
Micropterigidae
Micropterigoidea is the superfamily of "mandibulate archaic moths", all placed in the single family Micropterigidae, containing currently about twenty living genera. They are considered the most primitive extant lineage of lepidoptera (Kristense ...
)
File:Gonepteryx.rhamni.mounted.jpg, Heteroneurous venation in ''
Gonepteryx rhamni
''Gonepteryx rhamni'' (known as the common brimstone) is a butterfly of the family Pieridae. It lives throughout the Palearctic zone and is commonly found across Europe, Asia, and North Africa. Across much of its range, it is the only species ...
'' (
Pieridae
The Pieridae are a large family of butterflies with about 76 genera containing about 1,100 species, mostly from tropical Africa and tropical Asia with some varieties in the more northern regions of North America and Eurasia.DeVries P. J. in Le ...
)
File:Synanthedon_tipuliformis_%28ento-csiro-au%29.jpg, Reduced venation in '' Synanthedon tipuliformis'' (
Sesiidae
The Sesiidae or clearwing moths are a diurnal moth family in the order Lepidoptera known for their Batesian mimicry in both appearance and behaviour of various Hymenoptera.
The family consists of 165 genera spread over two subfamilies, contai ...
)
Wing coupling
The Lepidoptera have developed a wide variety of morphological wing-coupling mechanisms in the imago which render these taxa "functionally dipterous" (two winged). All but the most basal forms exhibit this wing coupling. There are three different types of mechanisms – jugal, frenulo–retinacular, and amplexiform.Scoble (1995). Section "Wing coupling", (pp. 56–60).
The more primitive groups have an enlarged lobe-like area near the basal posterior margin (i.e. at the base of the forewing) called a ''jugum'', that folds under the hindwing during flight. Other groups have a
frenulum
A frenulum (or frenum, plural: frenula or frena, from the Latin ''frēnulum'', "little bridle", the diminutive of ''frēnum'') is a small fold of tissue that secures the motion of a mobile organ in the body.
In human anatomy
Frenula on the h ...
on the hindwing that hooks under a
retinaculum
A retinaculum (plural ''retinacula'') is a band of thickened deep fascia around tendons that holds them in place. It is not part of any muscle. Its function is mostly to stabilize a tendon. The term retinaculum is New Latin, derived from the Lati ...
Bombycoidea
Bombycoidea is a superfamily of moths. It contains the silk moths, emperor moths, sphinx moths
The Sphingidae are a family of moths ( Lepidoptera) called sphinx moths, also colloquially known as hawk moths, with many of their caterpillars ...
moths (with the exception of the
Sphingidae
The Sphingidae are a family of moths (Lepidoptera) called sphinx moths, also colloquially known as hawk moths, with many of their caterpillars known as “hornworms”; it includes about 1,450 species. It is best represented in the tropics, but ...
), there is no arrangement of frenulum and retinaculum to couple the wings. Instead, an enlarged humeral area of the hindwing is broadly overlapped by the forewing. Despite the absence of a specific mechanical connection, the wings overlap and operate in phase. The power stroke of the forewing pushes down the hindwing in unison. This type of coupling is a variation of frenate type but where the frenulum and retinaculum are completely lost.
Scales
The wings of Lepidoptera are minutely scaled, which gives the name to this order; the name ''Lepidoptera'' was coined in 1735 by
Carl Linnaeus
Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
for the group of "insects with four scaly wings". It is derived from
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
''lepis'' (λεπίς) meaning "(fish) scale" (and related to ''lepein'' "to peel") and ''pteron'' (πτερόν) meaning "wing". from Lepidoptera on Dictionary.com website.
Scales also cover the head, parts of the thorax and abdomen as well as parts of the genitalia. The morphology of scales has been studied by J. C. Downey and A. C. Allyn (1975) and scales have been classified into three groups, namely hair-like, or ''piliform'', blade-like, or ''lamellar'' and other variable forms.
Primitive moths (non-Glossata and Eriocranidae) have "solid" scales which are imperforate, i.e., they lack a lumen.
A few taxa of the
Trichoptera
The caddisflies, or order Trichoptera, are a group of insects with aquatic larvae and terrestrial adults. There are approximately 14,500 described species, most of which can be divided into the suborders Integripalpia and Annulipalpia on the b ...
(caddisflies), which are the sister group to the Lepidoptera, have hair-like scales, but always on the wings and never on the body or other parts of the insect. Caddisflies also possess caudal cerci on the abdomen, a feature absent in the Lepidoptera. According to Scoble (2005), "morphologically, scales are macrotrichia, and thus homologous with the large hairs (and scales) that cover the wings of Trichoptera (caddisflies)".
Structure
Although there is great diversity in scale form, they all share a similar structure. Scales, like other macrochaetes, arise from special trichogenic (hair-producing) cells and have a socket which is enclosed in a special "tormogen" cell; this arrangement provides a stalk or ''pedicel'' by which scales are attached to the substrate. Scales may be piliform (hairlike) or flattened. The body or "blade" of a typical flattened scale consists of an upper and lower lamella with an air space in between. The surface towards the body is smooth and known as the ''inferior'' lamella. The upper surface, or ''superior'' lamella, has transverse and longitudinal ridges and ribs. The lamellae are held apart by struts called ''trabaculae'' and contain pigments which give colour. The scales cling somewhat loosely to the wing and come off easily without harming the butterfly.
Colour
The scales on butterfly wings are pigmented with
melanin
Melanin (; from el, μέλας, melas, black, dark) is a broad term for a group of natural pigments found in most organisms. Eumelanin is produced through a multistage chemical process known as melanogenesis, where the oxidation of the amino ...
s that can produce the colours black and brown. The white colour in the butterfly family
Pieridae
The Pieridae are a large family of butterflies with about 76 genera containing about 1,100 species, mostly from tropical Africa and tropical Asia with some varieties in the more northern regions of North America and Eurasia.DeVries P. J. in Le ...
is a derivative of
uric acid
Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates, such as ammonium acid urate. Uric acid is a product of the metabolic breakdown ...
, an excretory product. Bright blues, greens, reds, and iridescence are usually created not by pigments but through the microstructure of the scales. This
structural coloration
Structural coloration in animals, and a few plants, is the production of colour by microscopically structured surfaces fine enough to interfere with visible light instead of pigments, although some structural coloration occurs in combination wi ...
is the result of
coherent scattering
Scattering is a term used in physics to describe a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including ...
of light by the
photonic crystal
A photonic crystal is an optical nanostructure in which the refractive index changes periodically. This affects the propagation of light in the same way that the structure of natural crystals gives rise to X-ray diffraction and that the atomic ...
nature of the scales. The specialised scales that provide structural colours to reflected light mostly produce ultraviolet patterns which are discernible in that part of the ultraviolet spectrum that lepidopteran eyes can see. The structural colour seen is often dependent upon the angle of view. For example, in '' Morpho cypris'', the colour from the front is a bright blue but when seen from an angle changes very quickly to black.
The iridescent structural coloration on the wings of many lycaenid and papilionid species, such as ''
Parides sesostris
''Parides sesostris'', the emerald-patched cattleheart or southern cattleheart, is a species of butterfly in the family Papilionidae.
Subspecies
* ''Parides sesostris sesostris'' (Cramer, 1779) (Suriname to eastern Ecuador and south to northern ...
'' and ''
Teinopalpus imperialis
''Teinopalpus imperialis'', the Kaisar-i-Hind, is a rare species of swallowtail butterfly found from Nepal and north India east to north Vietnam. The common name literally means "emperor of India". The Kaisar-i-Hind is much sought after by butte ...
'', and lycaenids such as ''
Callophrys rubi
The green hairstreak (''Callophrys rubi'') is a small butterfly in the family Lycaenidae.
Etymology
The genus name ''Callophrys'' is a Greek word meaning "beautiful eyebrows", while the species Latin name ''rubi'' derives from ''Rubus'' (brambl ...
'', '' Cyanophrys remus'', and '' Mitoura gryneus'', has been studied. They manifest the most complex photonic scale architectures known – regular three-dimensional periodic lattices, that occur within the lumen of some scales. In the case of the Kaiser-i-Hind (''
Teinopalpus imperialis
''Teinopalpus imperialis'', the Kaisar-i-Hind, is a rare species of swallowtail butterfly found from Nepal and north India east to north Vietnam. The common name literally means "emperor of India". The Kaisar-i-Hind is much sought after by butte ...
''), the three-dimensional photonic structure has been examined by transmission electron tomography and computer modelling to reveal naturally occurring "chiral tetrahedral repeating units packed in a triclinic lattice", the cause of the iridescence.
File:Morphocypris2.JPG, Structural blue colour in '' morpho cypris'', a nymphalid
File:Morphocyprislateral.JPG, When the same ''Morpho cypris'' specimen is seen end on, the blue colour turns black.
File:Common_Jezebel_Delias_eucharis_edit_by_kadavoor.jpg, The white colour in pierids, such as '' Delias eucharis'' is a derivative of uric acid, an excretory product.
File:Teinopalpus imperialis Male.jpg, The green iridescence of the swallowtail Kaiser-i-Hind (''
Teinopalpus imperialis
''Teinopalpus imperialis'', the Kaisar-i-Hind, is a rare species of swallowtail butterfly found from Nepal and north India east to north Vietnam. The common name literally means "emperor of India". The Kaisar-i-Hind is much sought after by butte ...
'') led to the discovery of three-dimensional
photonic crystal
A photonic crystal is an optical nanostructure in which the refractive index changes periodically. This affects the propagation of light in the same way that the structure of natural crystals gives rise to X-ray diffraction and that the atomic ...
structure.
File:Colostygia_aqueata_Buchstein01.jpg, Wing coloration in certain Lepidoptera permits camouflage as can be seen in the case of the geometrid moth '' Colostygia aqueata''.
Function
Scales play an important part in the natural history of Lepidoptera. Scales enable the development of vivid or indistinct
patterns
A pattern is a regularity in the world, in human-made design, or in abstract ideas. As such, the elements of a pattern repeat in a predictable manner. A geometric pattern is a kind of pattern formed of geometric shapes and typically repeated li ...
which help the organism protect itself by
camouflage
Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
insulation
Insulation may refer to:
Thermal
* Thermal insulation, use of materials to reduce rates of heat transfer
** List of insulation materials
** Building insulation, thermal insulation added to buildings for comfort and energy efficiency
*** Insulated ...
, dark patterns on wings allow sunlight to be absorbed and are probably involved in
thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
. Bright and distinctive colour patterns in butterflies which are distasteful to predators help
communicate
Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...
their toxicity or inedibility, thus preventing predation. In Batesian mimicry, wing colour patterns help edible lepidopterans mimic inedible models, while in
Müllerian mimicry
Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Mülleria ...
, inedible butterflies resemble each other to reduce the numbers of individuals sampled by inexperienced predators.
Scales may have evolved initially for providing insulation. Scales on the thorax and other parts of the body may contribute to maintaining the high body temperatures required during flight. The "solid" scales of basal moths are however not as efficient as those of their more advanced relatives as the presence of a lumen adds air layers and increases the insulation value. Scales also help increase the
lift to drag ratio
In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under give ...
in flight.
For newly emerged adults of most
myrmecophilous
Myrmecophily ( , ) is the term applied to positive interspecies associations between ants and a variety of other organisms, such as plants, other arthropods, and fungi. Myrmecophily refers to mutualistic associations with ants, though in its ...
Lycaenidae
Lycaenidae is the second-largest family of butterflies (behind Nymphalidae, brush-footed butterflies), with over 6,000 species worldwide, whose members are also called gossamer-winged butterflies. They constitute about 30% of the known butterf ...
, deciduous waxy scales provide some protection from predators as they emerge from the nest. In the case of the moth butterfly (''
Liphyra brassolis
''Liphyra brassolis'', the moth butterfly, is a butterfly found in South Asia, Southeast Asia and Australia that belongs to the lycaenid family. The larvae are predatory and feed on ant larvae. This is one of the largest species of lycaenid but ...
''), the caterpillars are unwelcome guests in nests of tree ants, feeding on ant larvae. The adults emerging from pupae are covered with soft, loose adhesive scales which rub off and stick on the ants as they make their way out of the nest after hatching.
Androconia
Male Lepidoptera possess special scales, called ''androconia'' (singular – ''androconium''), which have evolved as a result of
sexual selection
Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ( ...
for the purposes of disseminating
pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
s for attracting suitable mates. Androconia may be dispersed on the wings, body, or legs or occur in patches, referred to as "brands", "sex brands" or "stigmata" on the wings, usually in
invagination
Invagination is the process of a surface folding in on itself to form a cavity, pouch or tube. In developmental biology, invagination is a mechanism that takes place during gastrulation. This mechanism or cell movement happens mostly in the vegeta ...
s of the upper surface of the forewings, sometimes concealed by other scales. Androconia are also known to occur in the folds of wings. These brands sometimes consist of hairlike tufts which facilitate the diffusion of the pheromone. The role of androconia in the courtship of pierid and nymphalid butterflies, such as '' Pyronia tithonus'' and ''
Dryas iulia
''Dryas iulia'' (often incorrectly spelled ''julia''),Lamas, G. (editor) (2004). Atlas of Neotropical Lepidoptera. Checklist: Part 4A. Hesperioidea – Papilionoidea. commonly called the Julia butterfly, Julia heliconian, the flame, or flambeau ...
'', has been proven experimentally.
Successive close-ups of the scales of a peacock wing
Abdomen
The
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...
or body is composed of nine segments. In the larva it ranges from segments 5 to 13. The eleventh segment of the larva holds a pair of anal claspers, which protrude in some
taxa
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
and represent the genitalia.
Many families of moths have special organs to help detect bat echolocation. These organs are known as '' tympana'' (singular – ''typanum''). The Pyraloidea and almost all
Geometroidea
The Geometroidea are the superfamily of geometrid moths in the order Lepidoptera. It includes the families Geometridae, Uraniidae, Epicopeiidae, Sematuridae, and the recently established family Pseudobistonidae.
The monotypic genus ''Apoprogones
...
have tympana located on the anterior sternite of the abdomen. The
Noctuoidea
Noctuoidea is the superfamily of noctuid (Latin "night owl") or "owlet" moths, and has more than 70,000 described species, the largest number of for any Lepidopteran superfamily. Its classification has not yet reached a satisfactory or stable st ...
also have tympana, but in their case, the tympana are located on the underside of the
metathorax
The metathorax is the posterior of the three segments in the thorax of an insect, and bears the third pair of legs. Its principal sclerites ( exoskeletal plates) are the metanotum (dorsal), the metasternum (ventral), and the metapleuron (lateral) ...
, the structure and position of which are unique and a taxonomic distinguishing feature of the superfamily.
The females of some moths have a scent-emitting organ located at the tip of the abdomen.
Genitalia
The
genitalia
A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...
are complex and provide the basis for species discrimination in most families and also in family identification. The genitalia arise from the tenth or most distal segment of the abdomen. Lepidoptera have some of the most complex genital structures of all insects, with a wide variety of complex spines, setae, scales and tufts in males, claspers of different shapes and modifications of the ''ductus bursae'' in females, through which stored sperm is transferred within the female directly, or indirectly, to the vagina for fertilisation.Scoble (1995). Section "Adult abdomen", (pp. 98–102).
The arrangement of genitalia is important in courtship and mating as they prevent cross-specific mating and hybridisation. The uniqueness of a species' genitalia led to the use of the morphological study of genitalia as one of the most important keys in taxonomic identification of taxa below family level. With the advent of DNA analysis, the study of genitalia has now become just one of the techniques used in taxonomy.
There are three basic configurations of genitalia in the majority of the Lepidoptera based on how the arrangement in females of openings for copulation, fertilisation and egg laying has evolved:
* ''
Exoporia
The Exoporia are a group of primitive Lepidoptera comprising the superfamilies Mnesarchaeoidea and Hepialoidea.Nielsen, E.S., Robinson, G.S. and Wagner, D.L. 2000. Ghost-moths of the world: a global inventory and bibliography of the Exoporia (Mne ...
n'':
Hepialidae
The Hepialidae are a family of insects in the lepidopteran order. Moths of this family are often referred to as swift moths or ghost moths.
Taxonomy and systematics
The Hepialidae constitute by far the most diverse group of the infraorder Exop ...
and related families have an external groove that carries sperm from the copulatory opening (gonopore) to the (ovipore) and are termed Exoporian.
* ''
Monotrysia
The Monotrysia are a group of moths in the lepidopteran order, not currently considered to be a natural group or clade. Apart from the recently discovered family
Family (from la, familia) is a group of people related either by consanguinit ...
n'': Primitive groups have a single genital aperture near the end of the abdomen through which both copulation and egg laying occur. This character is used to designate the Monotrysia.
* ''
Ditrysia
The Ditrysia are a natural group or clade of insects in the lepidopteran order containing both butterflies and moths. They are so named because the female has two distinct sexual openings: one for mating, and the other for laying eggs (in contr ...
n'': The remaining groups have an internal duct that carry sperm and form the Ditrysia, with separate openings for copulation and egg laying.
The genitalia of the male and female in any particular species are adapted to fit each other like a lock (male) and key (female). In males, the ninth abdominal segment is divided into a
dorsal
Dorsal (from Latin ''dorsum'' ‘back’) may refer to:
* Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism
* Dorsal, positioned on top of an aircraft's fuselage
* Dorsal c ...
"tegumen" and
ventral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
"viniculum". They form a ring-like structure for the attachment of genital parts and a pair of lateral clasping organs (claspers or "harpe"). The male has a median tubular organ (called the aedeagus) which is extended through an eversible sheath (or "vesica") to inseminate the female. The males have paired sperm ducts in all lepidopterans; the paired testes are separate in basal taxa and fused in advanced forms.
While the layout of internal genital ducts and openings of the female genitalia depends upon the taxonomic group that insect belongs to, the internal female reproductive system of all lepidopterans consists of paired ovaries and accessory glands which produce the yolks and shells of the eggs. Female insects have a system of receptacles and ducts in which sperm is received, transported, and stored. The oviducts of the female join together to form a common duct (called the "oviductus communis") which leads to the vagina.
When copulation takes place, the male butterfly or moth places a capsule of sperm (
spermatophore
A spermatophore or sperm ampulla is a capsule or mass containing spermatozoa created by males of various animal species, especially salamanders and arthropods, and transferred in entirety to the female's ovipore during reproduction. Spermatophores ...
) in a receptacle of the female (called the ''corpus bursae''). The sperm, when released from the capsule, swims directly into or via a small tube into a special seminal receptacle (
spermatheca
The spermatheca (pronounced plural: spermathecae ), also called receptaculum seminis (plural: receptacula seminis), is an organ of the female reproductive tract in insects, e.g. ants, bees, some molluscs, oligochaeta worms and certain other in ...
), where the sperm is stored until it is released into the vagina for fertilisation during egg laying, which may occur hours, days, or months after mating. The eggs pass through the
ovipore
An ovipore is a pore-like sexual organ of a female insect that is inseminated by the spermatophores ejected by the aedeagus of a male insect during copulation. The spermatophores that pass through the ovipore are stored in most insect species i ...
. The ovipore may be at the end of a modified ovipositor or surrounded by a pair of broad setose anal papillae.
Butterflies of the Parnassinae (family Papilionidae) and some
Acraeini
The Acraeini are a tribe of butterflies of the subfamily Heliconiinae in the family Nymphalidae.
Genera
The recognized genera are: Tree of Life
* '' Abananote'' Potts, 1943
* ''Acraea'' Fabricius, 1807 – acraeas
* '' Actinote'' Hübner, 8 ...
(family Nymphalidae) add a post-copulatory plug, called the sphragis, to the abdomen of the female after copulation preventing her from mating again.
The males of many species of Papilionoidea are furnished with secondary sexual characteristics. These consist of scent-producing organs, brushes, and brands or pouches of specialised scales. These presumably meet the function of convincing the female that she is mating with a male of the correct species.
Three species of hawkmoth have been recorded to emit ultrasound clicks by rubbing their genitalia; males produce by rubbing rigid scales on the exterior of the ''claspers'' while females produce sound by contracting their genitalia which causes rubbing of scales against the abdomen. The function of this noise making is not clear and suggestions put forward include the jamming of bat echolocation, and, advertising that the bat's prey are prickly and excellent fliers.
File:Citheronia regalis closed claspers, MM.jpg, ''
Citheronia regalis
''Citheronia regalis'', the regal moth or royal walnut moth, is a North American moth in the family Saturniidae. The caterpillars are called hickory horned devils. The adult (imago) has a wingspan of . The species was first described by Johan Chri ...
'' with claspers closed
File:Citheronia regalis open claspers, MM.jpg, ''
Citheronia regalis
''Citheronia regalis'', the regal moth or royal walnut moth, is a North American moth in the family Saturniidae. The caterpillars are called hickory horned devils. The adult (imago) has a wingspan of . The species was first described by Johan Chri ...
'' with claspers open
File:Parnassius apollo - 01 (HS).jpg, Female
with sphragis or mating plug
File:Parnassius apollo - sphragis 02 (HS).jpg, Close up of the hardened sphragis extruding 2 to 3 mm behind the abdomen of ''
Parnassius
''Parnassius'' is a genus of northern circumpolar and montane (alpine and Himalayan) butterflies usually known as Apollos or snow Apollos. They can vary in colour and form significantly based on their altitude. They also show an adaptation to h ...
''
Cloaca
Lepidopteran insects feature a cloaca at the end of the abdomen. This may be complete, incorporating the anus, the
ovipore
An ovipore is a pore-like sexual organ of a female insect that is inseminated by the spermatophores ejected by the aedeagus of a male insect during copulation. The spermatophores that pass through the ovipore are stored in most insect species i ...
Dacnonypha
Eriocraniidae is a family of moths restricted to the Holarctic region, with six extant genera. These small, metallic moths are usually day-flying, emerging fairly early in the northern temperate spring. They have a proboscis with which they drin ...
,
Zeugloptera
Micropterigoidea is the superfamily of "mandibulate archaic moths", all placed in the single family Micropterigidae, containing currently about twenty living genera. They are considered the most primitive extant lineage of lepidoptera (Kristense ...
and the majority of the
Monotrysia
The Monotrysia are a group of moths in the lepidopteran order, not currently considered to be a natural group or clade. Apart from the recently discovered family
Family (from la, familia) is a group of people related either by consanguinit ...
; or incomplete, incorporating the anus and ovipore only, as found in some of the Monotrysia, the
Psychidae
The Psychidae (bagworm moths, also simply bagworms or bagmoths) are a family of the Lepidoptera ( butterflies and moths). The bagworm family is fairly small, with about 1,350 species described. Bagworm species are found globally, with some, ...
, and in some
Choreutidae
Choreutidae, or metalmark moths, are a family of insects in the lepidopteran order whose relationships have been long disputed. It was placed previously in the superfamily Yponomeutoidea in family Glyphipterigidae and in superfamily Sesioide ...
and
Cossidae
The Cossidae, the cossid millers or carpenter millers, make up a family of mostly large miller moths. This family contains over 110 genera with almost 700 known species, and many more species await description. Carpenter millers are nocturnal ...
.
Development
The fertilised egg matures and hatches to give a caterpillar. The caterpillar is the feeding stage of the lepidopteran life cycle. The caterpillar needs to be able to feed and to avoid being eaten and much of its morphology has evolved to facilitate these two functions.Scoble (1995). Chapter "Immature stages", (pp. 104–133). After growth and ecdysis, the caterpillar enters into a
sessile
Sessility, or sessile, may refer to:
* Sessility (motility), organisms which are not able to move about
* Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant
* Sessility (medicine), tumors and polyps that ...
developmental stage called a pupa (or chrysalis) around which it may form a casing. The insect develops into the adult in the pupa stage; when ready the pupa hatches and the adult stage or imago of a butterfly or moth arises.
Egg
Like most insects, the Lepidoptera are oviparous or "egg layers". Lepidopteran eggs, like those of other insects, are centrolecithal in that the eggs have a central yolk surrounded by cytoplasm. The yolk provides the liquid nourishment for the embryo caterpillar until it escapes from the shell. The cytoplasm is enclosed by the vitteline envelope and a proteinaceous membrane called the chorion (egg), chorion protects the egg externally.Chapman (1998). Section "The egg and embryology" (pp. 325–362). The zygote nucleus is located posteriorly.
In some species of Lepidoptera, a waxy layer is present inside the chorion adjacent to the vitelline layer which is thought to have evolved to prevent desiccation. In insects, the chorion has a layer of air pores in the otherwise solid material which provides very limited capability for respiratory function. In Lepidoptera, the chorion layer above this air pore layer is lamellar with successive sheets of protein arranged in a particular direction and stepped so as to form a helical arrangement.
The top of the egg is depressed and forms a small central cavity called Micropyle (zoology), micropyle through which the egg is fertilised. The micropyle is situated on top in eggs which are globular, conical, or cylindrical; in those eggs which are flattened or lenticular, the micropyle is located on the outer margin or rim.
The eggs of Lepidoptera are usually rounded and small (1 mm) though they may be as large as 4 mm in the case of
Sphingidae
The Sphingidae are a family of moths (Lepidoptera) called sphinx moths, also colloquially known as hawk moths, with many of their caterpillars known as “hornworms”; it includes about 1,450 species. It is best represented in the tropics, but ...
and Saturniidae. They are generally quite plain in colour, white, pale green, bluish green, or brown. Butterfly and moth eggs come in various shapes; some are spherical, others hemispherical, conical, cylindrical, or lenticular (lens shaped). Some are barrel shaped or pancake shaped, while others are turban or cheese shaped. They may be angled or depressed at both ends, ridged or ornamented, spotted or blemished.
The eggs are deposited singly, in small clusters, or in a mass, and invariably on or near the food source. Captive moths have been known to lay eggs in the cages they have been sequestered in. Egg size in the Lepidoptera is affected by a number of factors. Lepidoptera species which hibernation, overwinter in the egg stage usually have larger eggs than the species that do not. Similarly, species feeding on woody plants in the larval stage have larger eggs than those species feeding on herbaceous plants. Eggs laid by older females of a few butterfly species have been noted to be smaller in size than their younger counterparts. In the absence of adequate nutrition, the females of the corn-borer moth ( ''Ostrinia'' spp.) have been recorded to lay clutches with egg sizes below normal.
While escaping, the newly hatched larvae of many species sometimes eat the chorion to emerge. Alternatively, the egg shell may have a line of weakness around the cap which gives way allowing the larva to emerge. The egg shell and a small amount of yolk trapped in the amniotic membranes forms the first food for most lepidopteran larvae.
File:Anaphaeis aurota eggs sec.jpg, Eggs of pioneer (''Anaphaeis aurota'' family Pieridae)
File:Pachliopta hector egg sec.jpg, Eggs of crimson rose (''Atrophaneura hector'' family Papilionidae)
File:Carcharodus alceae egg.jpg, Egg of mallow skipper (''Carcharodus alceae'' family Hesperiidae)
File:Lycaena dispar egg 2.jpg, Egg of large copper (''Lycaena dispar'' family Lycaenidae)
File:Archips goyerena eggs 0014170.jpg, Side by side eggs of ditrysian lepidopteran, baldcypress leafroller (''Archips goyerena'' family Tortricidae)
File:Actias luna eggs sjh.JPG, Upright eggs of ditrysian lepidopteran, moon moth (''Actias luna'' family Saturniidae) laid in captivity on paper
File:Bupalus_piniaria_ova.jpg, Eggs of pine looper moth (''Bupalus piniaria'' family Geometridae)
File:Malacosoma neustria eggs.jpg, Eggs of lackey moth (''Malacosoma neustria'' family Lasiocampidae)
Caterpillar
Caterpillars, are "characteristic Wiktionary:polypod, polypod larvae with cylindrical bodies, short thoracic legs and abdominal prolegs (pseudopods)". They have a toughened (
sclerotised
Sclerotin is a component of the cuticle of various Arthropoda, most familiarly insects. It is formed by cross-linking members of particular classes of protein molecules, a biochemical process called sclerotization, a form of tanning in which qui ...
) head capsule, mandibles (mouthparts) for chewing, and a soft tubular, segmented body, that may have hair-like or other projections, three pairs of true legs, and additional
proleg
A proleg is a small, fleshy, stub structure found on the ventral surface of the abdomen of most larval forms of insects of the order Lepidoptera, though they can also be found on other larval insects such as sawflies and a few other types of in ...
s (up to five pairs). The body consists of thirteen segments, of which three are thoracic (T1, T2, and T3) and ten are abdominal (A1 to A10).
All true caterpillars have an upside-down Y-shaped line that runs from the top of the head downward. In between the Y-shaped line lies the frontal triangle or frons. The Clypeus (arthropod anatomy), clypeus, located below the frons, lies between the two antenna (biology), antennae. The Insect mouthparts, labrum is found below the clypeus. There is a small notch in the centre of the labrum with which the leaf edge engages when the caterpillar eats.
The larvae have silk glands which are located on the labium (insect), labium. These glands are modified salivary glands. They use these silk glands to make silk for cocoons and shelters. Located below the labrum are the mandibles. On each side of the head there are usually six Simple eye in invertebrates#Stemmata, stemmata just above the mandibles. These stemmata are arranged in a semicircle. Below the stemmata there is a small pair of antennae, one on each side.
The thorax bears three pairs of legs, one pair on each segment. The prothorax (T1) has a functional spiracle which is actually derived from the mesothorax (T2) while the metathorax has a reduced spiracle which is not externally open and lies beneath the cuticle. The thoracic legs consist of coxa, trochanter, femur, tarsus, and claw and are constant in form throughout the order. However they are reduced in the case of certain leaf-miners and elongated in certain Notodontidae. In Micropterigidae, the legs are three-segmented, as the coxa, trochanter, and femur are fused.
Abdominal segments three through six and ten may each bear a pair of legs that are more fleshy. The thoracic legs are known as true legs and the abdominal legs are called prolegs. The true legs vary little in the Lepidoptera except for reduction in certain leaf-miners and elongation in the family Notodontidae. The prolegs contain a number of small hooks on the tip, which are known as crochets. The families of Lepidoptera differ in the number and positioning of their prolegs. Some larvae such as inchworms (Geometridae) and loopers (Plusiinae) have five pairs of prolegs or less, while others like
Lycaenidae
Lycaenidae is the second-largest family of butterflies (behind Nymphalidae, brush-footed butterflies), with over 6,000 species worldwide, whose members are also called gossamer-winged butterflies. They constitute about 30% of the known butterf ...
and slug caterpillars (Limacodidae) lack prolegs altogether. In some leaf-mining caterpillars there are crochets present on the abdominal wall which are reduced prolegs, while other leaf-mining species lack the crochets entirely. The abdominal spiracles are located on each side of the body on the first eight abdominal segments.
Caterpillars have different types of projections; setae (hairs), spines, warts, tubercles, and horns. The hairs come in an assortment of colours and may be long or short; single, in clusters, or in tufts; thinner at the point or clubbed at the end. A spine may either be a ''chalaza'' (having a single point) or a ''scolus'' (having multiple points). The warts may either be small bumps or short projections on the body. The tubercles are fleshy body projections that are either short and bump like or long and filament like. They usually occur in pairs or in a cluster on one or more segments. The horns are short, fleshy, and are drawn to a point. They are usually found on the eighth abdominal segment.
A large number of species of families Saturniidae, Limacodidae, and Megalopygidae have stinging caterpillars which have poisonous setae, called urticating hairs, and in the case of ''Lonomia'' – a Brazilian saturniid genus – can kill a human due to its potent anticoagulant poison. Caterpillars of many taxa that have sequestered toxic chemicals from host plants or have sharp urticating hair or spines, display aposematism, aposematic colouration and markings.
Caterpillars undergo ecdysis and have a number of larval
instar
An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...
s, usually five but varying between species. The new cuticle is soft and allows the increase in size and development of the caterpillar before becoming hard and inelastic. In the last ecdysis, the old cuticle splits and curls up into a small ball at the posterior end of the pupa and is known as the larval exuvia.
File:Common mormon (Papilio Polyetes) catapillars.jpg, Two
instar
An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ...
s of the papilionid common Mormon with different camouflage schemes – resembling bird droppings and vegetation
File:Stauropus fagi3.jpg, The larvae of notodontid moths, such as that of ''Stauropus fagi'', have elongated thoracic legs.
File:Taturana.JPG, The larva of ''Lonomia obliqua'', a Saturniidae, saturniid moth from Brazil, has urticating hairs with a lethal anticoagulant poison.
File:Saddleback moth caterpillar.jpg, Saddleback moth (''Saddleback caterpillar, Acharia stimulea'') larvae display aposematic colouring in the shape of a saddle.
File:PhobUnderside.JPG, Underside of slug caterpillars of ''Phobetron pithecium'' (family Limacododiae) showing the absence of prolegs
File:Phyllocnistis populiella damage2.jpg, Caterpillar of common aspen leafminer (''Phyllocnistis populiella'')
File:Hypsipyla.jpg, The mahogany shoot-borer (''Hypsipyla grandella'') damages mahogany in Brazil.
File:Family Psychidae444.jpg, Bagworm caterpillar (possibly ''Hyalarcta huebneri'' family
Psychidae
The Psychidae (bagworm moths, also simply bagworms or bagmoths) are a family of the Lepidoptera ( butterflies and moths). The bagworm family is fairly small, with about 1,350 species described. Bagworm species are found globally, with some, ...
) emerging from its case
File:Blue Mormon Larva.jpg, Last instar of blue Mormon larva-resembling vegetation
Chrysalis or pupa
A cocoon is a casing spun of silk by many moth caterpillars, and numerous other holometabolous insect
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
...
e as a protective covering for the pupa. Most Lepidoptera larvae will either make a pupa, cocoon and
pupate
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...
inside them or will pupate in a cell under the ground, with the exception of butterflies and advanced moths such as Noctuidae, noctuids, whose pupae are exposed. The pupae of moths are usually brown and smooth whereas butterfly pupae are often colourful and their shape varies greatly. In butterflies, the exposed pupa is often referred to as a chrysalis, derived from the Greek language, Greek term "chrysalis": (') for gold, referring to the golden colour of some pupae.
The caterpillars of many butterflies attach themselves by a button of silk to the underside of a branch, stone, or other projecting surface. They remain attached to the silk pad by a hook-like process called a cremaster. Most chrysalids hang head downward, but in the families Papilionidae, Pieridae, and Lycaenidae, the chrysalis is held in a more upright position by a silk girdle around the middle of the chrysalis.
The pupae of most Lepidoptera are ''obtect'', with appendages fused or glued to the body, while the rest have ''exarate'' pupae, having the antennae, legs, and wings free and not glued to the body.
During the pupal stage, the morphology of the adult is developed through elaboration from larval structures. The general aspect of the adult is visible before the outer surface hardens – the head, resting on the thorax, the eyes, antennae (brought forward over the head), the wings brought over the thorax, and the six legs between the wings and the abdomen. Among the features discernible in the head region of a pupa are sclerites, sutures, pilifers, mandibles, eye-pieces, antennae, palpi, and the maxillae. The pupal thorax displays the three thoracic segments, legs, wings, tegulae, alar furrows, and axillary tubercles. The pupal abdomen exhibits the ten segments, spines, setae, scars of larval prolegs and tubercles, anal, and genital openings, as well as spiracles. The pupa of borers display the flange-plates while those of specialised Lepidoptera exhibit the cremaster.
While the pupa is generally stationary and immobile, those of the primitive moth families
Micropterigidae
Micropterigoidea is the superfamily of "mandibulate archaic moths", all placed in the single family Micropterigidae, containing currently about twenty living genera. They are considered the most primitive extant lineage of lepidoptera (Kristense ...
, Agathiphagidae, and Heterobathmiidae have fully functional mandibles. These serve principally to allow the adult to escape from the cocoon. Besides this, all appendages and the body are separate from the pupal skin and enjoy a degree of independent motion. All other superfamilies of the Lepidoptera are more specialised, have non-functional mandibles, appendages and body attached to the pupal skin, and lose a degree of independent movement.
The pupae of some moths are able to wriggle their abdomen. The three caudal segments of the pupal abdomen (segments 8–10) are fixed; the other segments are movable to some degree. While the more evolved Lepidoptera can wriggle only the last two or three segments at the end of the abdomen, more basal taxa such as the
Micropterigidae
Micropterigoidea is the superfamily of "mandibulate archaic moths", all placed in the single family Micropterigidae, containing currently about twenty living genera. They are considered the most primitive extant lineage of lepidoptera (Kristense ...
can wriggle the remaining seven segments of the abdomen; this presumably helps them to protrude the anterior end from the pupal case before eclosion. The pupae of Hepialidae are able to move back and forth in the larval tunnel by wriggling, aided by projections on the back in addition to spines. Abdominal wriggling is considered to be of startle value and discouraging to predators. In the case of a few Sphingidae, hawk moths, such as ''Theretra latreillii'', the wriggling of the abdomens is accompanied by a rattling or clicking sound which adds to the startle effect.
In some species, such as ''Heliconius charithonia'', mating can occur inside the pupa of females by males.
File:Black_Swallowtail_Chrysalis_Megan_McCarty33.jpg, Papilionid chrysalids are typically attached to a substrate by the cremaster and with the head up held by a silk girdle.
File:Common_crow_pupa.jpg, Suspended golden-coloured nymphalid chrysalis of ''Euploea core''
File:Actias luna emergence sjh stabilised.gif, ''Actias luna'' (family Saturniidae) emerging from cocoon
File:Agrius convoluli (pupa).jpg, The specialised pupa of a sphingid moth, ''Agrius convolvuli'', can wriggle its abdomen making a clicking sound, which can have a startle effect.
Defense and predation
Lepidopterans are soft bodied, fragile, and almost defenseless while the immature stages move slowly or are immobile, hence all stages are exposed to predation by birds, small mammals, lizards, amphibians, invertebrate predators (notably parasitoid and parasitic wasps and fly, flies) as well as fungi and bacteria. To combat this, Lepidoptera have developed a number of strategies for defense and protection which include
camouflage
Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...
, aposematism, mimicry, and the development of threat patterns and displays.
Camouflage is an important defense strategy enabled by changes in body shape, colour, and markings. Some lepidopterans blend with the surroundings, making them difficult to be seen by predators. Caterpillars can be shades of green that match their host plant. Others resemble inedible objects, such as twigs or leaves. The larvae of some species, such as the common Mormon and the Papilio rutulus, western tiger swallowtail look like bird droppings.
Some species of Lepidoptera sequester or manufacture toxins which are stored in their body tissue, rendering them poisonous to predators; examples include the Monarch (butterfly), monarch butterfly in the Americas and ''Atrophaneura'' species in Asia. Predators that eat poisonous lepidopterans may become sick and vomit violently, and so learn to avoid those species. A predator who has previously eaten a poisonous lepidopteran may avoid other species with similar markings in the future, thus saving many other species as well. Toxic butterflies and larvae tend to develop bright colours and striking patterns as an indicator to predators about their toxicity. This phenomenon is known as aposematism.
Aposematism has also led to the development of mimicry complexes of Batesian mimicry, where edible species mimic aposematic taxa, and
Müllerian mimicry
Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Mülleria ...
, where inedible species, often of related taxa, have evolved to resemble each other, so as to benefit from reduced sampling rates by predators during learning. Similarly, adult
Sesiidae
The Sesiidae or clearwing moths are a diurnal moth family in the order Lepidoptera known for their Batesian mimicry in both appearance and behaviour of various Hymenoptera.
The family consists of 165 genera spread over two subfamilies, contai ...
species (also known as clearwing moths) have a general appearance that is sufficiently similar to a wasp or hornet to make it likely that the moths gain a reduction in predation by Batesian mimicry.
Eyespot (mimicry), Eyespots are a type of automimicry used by some lepidopterans. In butterflies, the spots are composed of concentric rings of scales of different colours. The proposed role of the eyespots is to deflect predators' attention. Their resemblance to eyes provokes the predator's instinct to attack these wing patterns. The role of filamentous tails in Lycaenidae has been suggested as confusing predators as to the real location of the head, giving them a better chance of escaping alive and relatively unscathed.
Some caterpillars, especially members of Papilionidae, contain an osmeterium, a Y-shaped protrusible gland found in the Prothorax, prothoracic segment of the larvae. When threatened, the caterpillar emits unpleasant smells from the organ to ward off the predators.
See also
* Differences between butterflies and moths
* Glossary of entomology terms
* Insect morphology
* Lepidoptera
* Morphology (biology)
Exquisite castaways – photo-feature on lepidopteran eggs by ''National Geographic''.
– photo-feature on moths by ''National Geographic''.
{{DEFAULTSORT:External Morphology of Lepidoptera
Lepidopterology
Insect morphology