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A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some
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 pa ...
s undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages thereof being egg,
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, and imago. The processes of entering and completing the pupal stage are controlled by the insect's hormones, especially juvenile hormone, prothoracicotropic hormone, and
ecdysone Ecdysone is a prohormone of the major insect molting hormone 20-hydroxyecdysone, which is secreted from the prothoracic glands. It is of steroidal structure. Insect molting hormones (ecdysone and its homologues) are generally called ecdysteroids. E ...
. The act of becoming a pupa is called pupation, and the act of emerging from the pupal case is called eclosion or emergence. The pupae of different groups of insects have different names such as ''chrysalis'' for the pupae of butterflies and ''tumbler'' for those of the mosquito family. Pupae may further be enclosed in other structures such as cocoons, nests, or shells.


Position in life cycle

The pupal stage follows 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. ...
l stage and precedes adulthood ('' imago'') in insects with complete metamorphosis. The pupa is a non-feeding, usually sessile stage, or highly active as in mosquitoes. It is during the pupal stage that the adult structures of the insect are formed while the larval structures are broken down. The adult structures grow from imaginal discs.


Duration

The pupal stage may last weeks, months, or even years, depending on temperature and the species of insect. For example, the pupal stage lasts eight to fifteen days in monarch butterflies. The pupa may enter dormancy or
diapause In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press I ...
until the appropriate season to emerge as an adult insect. In temperate climates pupae usually stay dormant during winter, while in the
tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...
pupae usually do so during the
dry season The dry season is a yearly period of low rainfall, especially in the tropics. The weather in the tropics is dominated by the tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year. The ...
.


Emergence

Insects emerge (eclose) from pupae by splitting the pupal case. Most butterflies emerge in the morning. In mosquitoes, the emergence is in the evening or night. In fleas, the process is triggered by vibrations that indicate the possible presence of a suitable host. Prior to emergence, the adult inside the pupal
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 ...
is termed ''pharate''. Once the pharate adult has eclosed from the pupa, the empty pupal exoskeleton is called an '' exuvia''; in most hymenopterans (ants, bees and wasps) the exuvia is so thin and membranous that it becomes "crumpled" as it is shed.


Pupal mating

In a few taxa of the Lepidoptera, especially '' Heliconius'', pupal mating is an extreme form of reproductive strategy in which the adult male mates with a female pupa about to emerge, or with the newly moulted female; this is accompanied by other actions such as capping of the reproductive system of the female with the sphragis, denying access to other males, or by exuding an anti-aphrodisiac pheromone.


Defense

Pupae are usually immobile and are largely defenseless. To overcome this, pupae often are covered with a cocoon, conceal themselves in the environment, or form underground. There are some species of Lycaenid butterflies which are protected in their pupal stage by ants. Another means of defense by pupae of other species is the capability of making sounds or vibrations to scare potential predators. A few species use chemical defenses including toxic secretions. The pupae of social hymenopterans are protected by adult members of the hive.


Types

Based on the presence or absence of articulated
mandible 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 ...
s that are employed in emerging from a cocoon or pupal case, the pupae can be classified in to two types: * Decticous pupa – a pupa with articulated mandibles. Examples are pupae of the orders Neuroptera, Mecoptera, Trichoptera and few Lepidoptera families. * Adecticous pupa – a pupa without articulated mandibles. Examples include the orders Strepsiptera, Coleoptera, Hymenoptera, Diptera and Siphonaptera. Based on whether the pupal appendages are free or attached to the body, the pupae can be classified as one of three types: * Exarate pupa – appendages are free and are not usually encapsulated within a cocoon. Decticous pupae are always exarate; some adecticous pupae are as well. (Neuroptera, Trichoptera,
Cyclorrhapha Cyclorrhapha is an unranked taxon within the infraorder Muscomorpha. They are called "Cyclorrhapha" ('circular-seamed flies') with reference to the circular aperture through which the adult escapes the puparium. This is a circumscriptional name t ...
of Dipterans, Siphonaptera, most Coleoptera, Hymenoptera, and few Lepidoptera). * Obtect pupa – appendages are attached closely to the body and are commonly encapsulated within a cocoon. Some adecticous pupa are obtect forms. (Most Lepidoptera,
Nematocera The Nematocera (the name means "thread-horns") are a suborder of elongated flies with thin, segmented antennae and mostly aquatic larvae. This group is paraphyletic and contains all flies but species from suborder Brachycera (the name means "sh ...
and
Brachycera The Brachycera are a suborder of the order Diptera. It is a major suborder consisting of around 120 families. Their most distinguishing characteristic is reduced antenna segmentation. Description A summary of the main physical characteristics i ...
of Dipterans,
Staphylinidae The rove beetles are a family (Staphylinidae) of beetles, primarily distinguished by their short elytra (wing covers) that typically leave more than half of their abdominal segments exposed. With roughly 63,000 species in thousands of genera, th ...
and
Chrysomelidae The insects of the beetle family Chrysomelidae are commonly known as leaf beetles, and include over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making up one of the largest and most commonly encountered of all beetle ...
Coleopterans, many Chalcidoidea Hymenopterans) * Coarctate pupa – enclosed in a hardened cuticle of the penultimate larval instar called a puparium. However, the pupa itself is of the exarate adecticous pupal form. (Cyclorrhapha of Dipterans).


Chrysalis

A chrysalis ( la, chrysallis, from grc, χρυσαλλίς, , plural: , also known as an ''aurelia'') or nympha is the pupal stage of butterflies. The term is derived from the metallic–gold coloration found in the pupae of many butterflies, referred to by the Ancient Greek term () for gold. When the caterpillar is fully grown, it makes a button of silk which it uses to fasten its body to a leaf or a twig. Then the caterpillar's skin comes off for the final time. Under this old skin is a hard skin called a chrysalis. Because chrysalises are often showy and are formed in the open, they are the most familiar examples of pupae. Most chrysalides are attached to a surface by a Velcro-like arrangement of a
silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from th ...
en pad spun by the caterpillar, usually cemented to the underside of a perch, and the ''cremastral'' hook or hooks protruding from the rear of the chrysalis or ''cremaster'' at the tip of the pupal
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 ...
by which the caterpillar fixes itself to the pad of silk. ( 'suspended') Like other types of pupae, the chrysalis stage in most butterflies is one in which there is little movement. However, some butterfly pupae are capable of moving the abdominal segments to produce sounds or to scare away potential predators. Within the chrysalis, growth and differentiation occur. The adult butterfly emerges (ecloses) from this and expands its wings by pumping haemolymph into the wing veins. Although this sudden and rapid change from pupa to imago is often called metamorphosis, metamorphosis is really the whole series of changes that an insect undergoes from egg to adult. When emerging, the butterfly uses a liquid, sometimes called
cocoonase Cocoonase is a trypsin-like proteolytic enzyme produced by silkworms (of both ''Bombyx'' and ''Antheraea'' species) as they near the final stages of their metamorphosis. It is produced by cells in the proboscis and exuded onto the galeae. Its fu ...
, which softens the shell of the chrysalis. Additionally, it uses two sharp claws located on the thick joints at the base of the forewings to help make its way out. Having emerged from the chrysalis, the butterfly will usually sit on the empty shell in order to expand and harden its wings. However, if the chrysalis was near the ground (such as if it fell off from its silk pad), the butterfly would find another vertical surface to rest upon and harden its wings (such as a wall or fence). Moth pupae are usually dark in color and either formed in underground cells, loose in the soil, or their pupa is contained in a protective
silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from th ...
case called a ''cocoon''. The pupa of some species such as the hornet moth develop sharp ridges around the outside called adminicula that allow the pupa to move from its place of concealment inside a tree trunk when it is time for the adult to emerge. Pupa, chrysalis, and cocoon are frequently confused, but are quite distinct from each other. The pupa is the stage between the larva and adult stages. The chrysalis generally refers to a butterfly pupa although the term may be misleading as there are some moths whose pupae resembles a chrysalis, e.g.: the plume winged moths of the family Pterophoridae and some geometrid moths. A cocoon is a silk case that the larvae of moths, and sometimes other insects, spin around the pupa.


Cocoon

A cocoon is a casing spun of
silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from th ...
by many moths and 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. Cocoons may be tough or soft, opaque or translucent, solid or meshlike, of various colors, or composed of multiple layers, depending on the type of insect larva producing it. Many moth caterpillars shed the larval hairs (
seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...
e) and incorporate them into the cocoon; if these are urticating hairs then the cocoon is also irritating to the touch. Some larvae attach small twigs, fecal pellets or pieces of vegetation to the outside of their cocoon in an attempt to disguise it from predators. Others spin their cocoon in a concealed location—on the underside of a
leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ...
, in a
crevice A crevice is a fracture or fissure in rock. Crevice may also refer to: * Crevice corrosion, occurs in spaces to which the access of corrosion-resistant fluid is limited * Crevice kelpfish (''Gibbonsia montereyensis''), a species of subtropical c ...
, down near the base of a tree trunk, suspended from a twig or concealed in the
leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constituent ...
. The silk in the cocoon of the
silk moth The domestic silk moth (''Bombyx mori''), is an insect from the moth family Bombycidae. It is the closest relative of ''Bombyx mandarina'', the wild silk moth. The silkworm is the larva or caterpillar of a silk moth. It is an economically im ...
can be unraveled to harvest silk fibre which makes this moth the most economically important of all lepidopterans. The silk moth is the only completely domesticated lepidopteran and does not exist in the wild. Insects that pupate in a cocoon must escape from it, and they do this either by the pupa cutting its way out, or by secreting
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
s, sometimes called
cocoonase Cocoonase is a trypsin-like proteolytic enzyme produced by silkworms (of both ''Bombyx'' and ''Antheraea'' species) as they near the final stages of their metamorphosis. It is produced by cells in the proboscis and exuded onto the galeae. Its fu ...
, that soften the cocoon. Some cocoons are constructed with built-in lines of weakness along which they will tear easily from inside, or with exit holes that only allow a one-way passage out; such features facilitate the escape of the adult insect after it emerges from the pupal skin.


Puparium

Some pupae remain inside the exoskeleton of the final larval instar and this last larval "shell" is called a puparium (plural, puparia). Flies of the group Muscomorpha have puparia, as do members of the order Strepsiptera, and the Hemipteran family
Aleyrodidae Whiteflies are Hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only family in the superfamily Aleyrodoidea. More than 1550 species have been described. Description and taxonomy The A ...
.


Gallery

File:Fruit Fly Pupa.jpg, Fruit fly ('' Drosophila melanogaster'') pupa File:Caterpillar making cocoon2.jpg, An emperor gum moth caterpillar spinning its cocoon File:Actias luna pupa 2 sjh.JPG, Luna moth cocoon and pupa File:Actias luna cocoons sjh.JPG, Assortment of Luna moth cocoons File:Actias luna emergence sjh.gif, Luna moth emerging from pupa within silk cocoon File:Actias luna pupa sjh enhanced.JPG, Luna moth pupa removed from cocoon File:Chrysalis5504.jpg, Chrysalis of Gulf fritillary File:Pupation - Inachis io.jpg, Pupation of ''
Aglais io ''Aglais io'', the European peacock, more commonly known simply as the peacock butterfly, is a colourful butterfly, found in Europe and temperate Asia as far east as Japan. It was formerly classified as the only member of the genus ''Inachis'' ...
'' File:Monarch Butterfly Chrysalis.JPG, Monarch butterfly chrysalis File:Nacimiento de una Dryas iulia, Mariposario de Icod de los Vinos, Tenerife, España, 2012-12-13, DD 03.jpg, Specimen of an eclosing ''
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 ...
'' butterfly File:Pupae of Japanagromyza inferna Spencer in gall of Centrosema virginianum L. - ZooKeys-374-045-g005.jpg, Pupae of ''Japanagromyza inferna'', a gall fly, in gall of ''
Centrosema virginianum ''Centrosema virginianum'' is known by the common names of Spurred Butterfly Pea, wild blue vine, blue bell, and wild pea. ''C. virginianum'' is a member of the family Fabaceae, it is identified by its trailing and twining vine and showy fl ...
'' File:Cabbage looper in cocoon.jpg, Pupa of cabbage looper File:BARON BUTTERFLY CHRYSALIS.jpg, Pupa of Baron Butterfly Euthalia aconthea File:Papilio polytes common Mormon pupa vijayanrajapuram 03.jpg, Papilio_polytes_common_Mormon_pupa on curry leaves.


See also

*
Brood (honeybee) In beekeeping, bee brood or brood refers to the eggs, larvae and pupae of honeybees. The brood of Western honey bees develops within a bee hive. In man-made, removable frame hives, such as Langstroth hives, each frame which is mainly occupied by ...
*
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. ...
*
Silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from th ...


References


External links


Pupa photos
plus species descriptions at ''Insecta.pro''
Silk worm life cycle photos
{{Authority control Insect physiology Insect developmental biology Articles containing video clips