Hypermetamorphosis, or heteromorphosis,P.J. Gullan & P.S. Cranston. 2010. The Insects: An Outline of Entomology, 4th Edition. Wiley-Blackwell. is a term used in

entomology Entomology () is the scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such as ara ...

that refers to a class of variants of

holometabolism 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 Endopterygota ...

, that is to say, complete

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 ...

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

, but where some

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. ...

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 are distinct from each other.

Description

Hypermetamorphosis, as the term normally is used in entomology, refers to a class of variants of

. 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 Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced m ...

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, 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 ( el, label= Modern Greek, Ελληνικά, Elliniká, ; grc, Ἑλληνική, Hellēnikḗ) is an independent branch of the Indo-European family of languages, native to Greece, Cyprus, southern Italy ( Calabria and Salento), souther ...

''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 insects in the genus ''

Campodea ''Campodea'' is a genus of small, white, bristle-tailed arthropods in the order Diplura The order Diplura ("two-pronged bristletails") is one of three orders of non-insect hexapods within the class Entognatha (alongside Collembola (springta ...

''). 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 in other insects, such as bees, wasps, leafhoppers, silverfish, and cockroaches. Females of most species never ...

, may also be called triungula. In their planidial form, many species do not feed; they first change their skin and change their bodily form to 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. 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 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 ...

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 leaf-green.

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 egg to adult. The term can also be used to refer to the s ...

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 ...

s, notably: * the

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

families

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 pa ...

, * the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

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. Adults generally feed on nectar and pollen, some being important pollinators. Larvae are mostly parasitoids of other insects. Overview The Bombyliidae are a large family of fl ...

and

Nemestrinidae Nemestrinidae, or tangle-veined flies is a family of flies in the superfamily Nemestrinoidea, closely related to Acroceridae. The family is small but distributed worldwide, with about 300 species in 34 genera. Larvae are endoparasitoids of eith ...

, * The

Neuroptera The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order consists of some 6,000 species. Neuroptera can be grouped together with the Megaloptera and Raphidioptera in th ...

n family Mantispidae 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.Ayre, G.L. Pseudometagea schwarzii (Ashm.) (Eucharitidae: Hymenoptera), a parasite of Lasius neoniger Emery (Formicidae: Hymenoptera). Canadian Journal of Zoology 40 (1962) : 157-164. Eucharitid ...

. 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 (from Greek ''analogia'', "proportion", from ''ana-'' "upon, according to" lso "against", "anew"+ ''logos'' "ratio" lso "word, speech, reckoning" is a cognitive process of transferring information or meaning from a particular subject ...

and not homologous to those in any other order; for example, hypermetamorphosis in the Acroceridae was not derived from the Strepsiptera, much less the Ephemeroptera.

References

{{reflist Insect developmental biology