Hypermetamorphic
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Hypermetamorphosis, or heteromorphosis, is a term used mainly in
entomology Entomology (from Ancient Greek ἔντομον (''éntomon''), meaning "insect", and -logy from λόγος (''lógos''), meaning "study") is the branch of zoology that focuses on insects. Those who study entomology are known as entomologists. In ...
; it refers to a class of variants of
holometabolism Holometabolism, also called complete metamorphosis (biology), metamorphosis, is a form of insect development which includes four life stages: egg (biology), egg, larva, pupa, and imago (or adult). Holometabolism is a synapomorphy, synapomorphic tr ...
, that is to say, complete
insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...
. Hypermetamorphosis is exceptional in that some
instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...
s, usually
larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...
l instars, are functionally and visibly distinct from the rest. The differences between such instars usually reflect transient stages in the life cycle; for instance, one instar might be mobile while it searches for its food supply, while the following instar immediately sheds its locomotory organs and settles down to feed until it is fully grown and ready to change into the reproductive stage, which in turn, does not have the same nutritional requirements as the larvae.


Description

Hypermetamorphosis, as the term normally is used in entomology, refers to a class of variants of
holometabolism Holometabolism, also called complete metamorphosis (biology), metamorphosis, is a form of insect development which includes four life stages: egg (biology), egg, larva, pupa, and imago (or adult). Holometabolism is a synapomorphy, synapomorphic tr ...
. In hypermetamorphosis some larval instars are functionally and morphologically distinct from each other. The general case in holometabolous insects such as
flies Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwin ...
,
moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...
s, or
wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder ...
s, is that all larval stages look similar, growing larger as the insect matures. In hypermetamorphic insects however, at least one instar, usually the first, differs markedly from the rest. In many hypermetamorphic species, the first instars are numerous, tiny, very mobile larvae that must find their way to a food source. The general term for a mobile first instar is a
planidium A planidium is a specialized form of insect larva seen in the first-instar of a few families of insects that have parasitoidal ways of life. They are usually flattened, highly sclerotized (hardened), and quite mobile. The function of the plani ...
, from the
Greek language Greek (, ; , ) is an Indo-European languages, Indo-European language, constituting an independent Hellenic languages, Hellenic branch within the Indo-European language family. It is native to Greece, Cyprus, Italy (in Calabria and Salento), south ...
''πλάνος'' (planos) meaning "roaming". In typical examples the first-instar larval morphology is campodeiform (meaning: elongated, flattened, and active, more or less resembling the morphology of hexapods in the genus ''
Campodea ''Campodea'' is a genus of small, white, bristle-tailed arthropods in the order Diplura. The best known species, ''Campodea staphylinus'', has a wide distribution across much of Europe. It lives in damp places under stones, fallen trees, or in ro ...
''). There is however, considerable variety in the forms of planidia that occur in various families and orders; in the beetle family
Meloidae Blister beetles are beetles of the family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. About 7,500 species are known worldwide. Many are conspicuous and some are aposematically colored, announcing their ...
, the three-clawed planidium originally was called a triungulin, and similar planidia for example, those of the
Strepsiptera The Strepsiptera () are an order of insects with eleven extant families that include about 600 described species. They are endoparasites of other insects, such as bees, wasps, leafhoppers, Zygentoma, silverfish, and cockroaches. Females of most s ...
, may also be called triungula. In their planidial form, many species do not feed; they then
molt In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at ...
into a form suited to eating rather than seeking out food. The second instar is completely different in appearance and behavior, often becoming grub- or maggot-like in the instars before pupation. As a rule, the instars after the first ecdysis are of more or less constant form and not highly mobile, being specialised for feeding and growth until the final larval instar metamorphoses into the pupal form. The moth 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, ''Cameraria ...
is an unusual case of hypermetamorphosis in that its first few larval instars do feed, but differently to later instars. Specifically, early instars feed on plant sap (and for this reason have modified mandibles) while later instars feed on plant tissue. Furthermore, instead of becoming less mobile during the larval stage, larvae become more mobile, with early instars lacking legs while later instars possess legs. There are examples of holometabolic species in which there are certain striking differences between the earliest instars and the later instars, though ''without'' their generally being regarded as hypermetamorphic. For example, early instars of many
Papilionidae Swallowtail butterflies are large, colorful Butterfly, 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 includ ...
are of a colour, shape and texture that suggest bird droppings; later instars that are larger and would simply stand out in such camouflage, typically become green. The
prepupa The prepupa is a stage in the life cycle of certain Insect, insects, following the larva or Nymph (biology), nymph and preceding the pupa. It occurs in both Holometabolism, holometabolous and Hemimetabolism, hemimetabolous insects. Examples ...
or last larval instar of insects ceases to feed and (in some cases) searches for a place to pupate, but this also is not considered hypermetamorphosis.


Various forms of hypermetamorphosis

Hypermetamorphosis usually occurs as an adaptation of the
ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the ovum, egg to adult. The term can also be used to refer to t ...
of certain
parasitoid In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
s, notably: * the
beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...
families
Meloidae Blister beetles are beetles of the family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. About 7,500 species are known worldwide. Many are conspicuous and some are aposematically colored, announcing their ...
and
Ripiphoridae Ripiphoridae (formerly spelled Rhipiphoridae) is a cosmopolitan family of some 450 described species of beetles sometimes called "wedge-shaped beetles". Ripiphoridae are unusual among beetle families in that many species are hypermetamorphic p ...
, * the
order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...
Strepsiptera The Strepsiptera () are an order of insects with eleven extant families that include about 600 described species. They are endoparasites of other insects, such as bees, wasps, leafhoppers, Zygentoma, silverfish, and cockroaches. Females of most s ...
, * the
moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...
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, ''Cameraria ...
, *
flies Flies are insects of the Order (biology), order Diptera, the name being derived from the Ancient Greek, Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwin ...
in the families
Acroceridae The Acroceridae are a small family of odd-looking flies. They have a hump-backed appearance with a strikingly small head, generally with a long proboscis for accessing nectar. They are rare and not widely known. The most frequently applied common ...
,
Bombyliidae The Bombyliidae are a family of flies, commonly known as bee flies. Some are colloquially known as bomber flies. Adults generally feed on nectar and pollen, some being important pollinators. Larvae are mostly parasitoids of other insects. Over ...
and
Nemestrinidae Nemestrinidae, or tangle-veined flies is a family of flies in the superfamily Nemestrinoidea, closely related to Acroceridae. Larvae are endoparasitoids of either grasshoppers (Trichopsideinae) or scarab beetles (Hirmoneurinae). Some are co ...
, * The
Neuroptera The insect order (biology), order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order consists of some 6,000 species. Neuroptera is grouped together with the Megaloptera (alderflies, f ...
n family
Mantispidae Mantispidae (), commonly known as mantidflies, mantispids, mantid lacewings, mantisflies or mantis-flies, is a family of small to moderate-sized insects in the order Neuroptera. There are many genera with around 400 species worldwide, especially ...
and * the
parasitic wasp Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps ( Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causi ...
family
Eucharitidae The Eucharitidae are a family of parasitic wasps. Eucharitid wasps are members of the superfamily Chalcidoidea and consist of four subfamilies: Akapalinae, Eucharitinae, Gollumiellinae, and Oraseminae. Most of the 42 genera and >400 species o ...
. Technically, the
subimago Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are aquatic insects belonging to the order ...
of the Ephemeroptera might be described as a stage in a form of hypermetamorphosis, but that is not common practice. Examples of hypermetamorphosis in any given insect order are
analogous Analogy is a comparison or correspondence between two things (or two groups of things) because of a third element that they are considered to share. In logic, it is an inference or an argument from one particular to another particular, as oppose ...
and not homologous to those in any other order; for example, hypermetamorphosis in the Acroceridae was not derived from the Strepsiptera.


See also

* * * * * *


References

{{reflist Insect developmental biology