Holometabolism

Holometabolism

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Holometabolism, also called complete metamorphism, is a term applied to insect groups to describe the specific kind of insect development which includes four life stages - as an embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 or egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

, a larva
Larva
A larva 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...

, a pupa
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...

 and an imago
Imago
In biology, the imago is the last stage of development of an insect, after the last ecdysis of an incomplete metamorphosis, or after emergence from the pupa where the metamorphosis is complete...

 or adult
Adult
An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age....

. Holometabolism is a monophyletic
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...

 trait that all insects in the Endopterygota
Endopterygota
The Endopterygota, also known as Holometabola, are insects of the subclass Pterygota which go through distinctive larval, pupal, and adult stages. They undergo a radical metamorphosis, with the larval and adult stages differing considerably in their structure and behaviour...

 superorder have. This type of development gives the offspring the unique advantage of not competing with adults because they inhabit different ecological niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

s due to the morphological differences in the different stages of their life cycle.

Embryo


The first stage is from the fertilization of the egg inside the mother until the embryo hatches. The insect starts as a single cell, and then develops into the larval form before it hatches.

Larva


The second stage is from birth until the larva pupates. This mobile stage is generally worm-like in form. This worm-like form can be one of several varieties: eruciform (caterpillar-like), scarabaeiform (grub-like), campodeiform (elongated, flattened, and active), elateriform (wireworm-like) or vermiform (maggot-like). This stage usually consists of growth and gaining stored energy for metamorphosis.

Pupa


The third stage is from pupation until eclosion. This stage is marked by reduced movement and often sealed within a cocoon
Pupa
A pupa is the life stage of some insects undergoing transformation. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago...

. There are three types of pupae: obtect, exarate or coarctate. Obtect pupae are compact, with the legs and other appendages enclosed. Exarate pupae have their legs and other appendages free and extended. Coarctate pupae develop inside the larval skin. In this stage, the insect's internals change drastically.

Imago


Adult holometabolous insects usually have wings (excepting where secondarily lost) and functioning reproductive organs. In this stage, reproduction is the top priority for Queens and males.

Orders


The Orders that contain holometabolous insects are :
  • Coleoptera - Beetles
  • Diptera
    Diptera
    Diptera , or true flies, is the order of insects possessing only a single pair of wings on the mesothorax; the metathorax bears a pair of drumstick like structures called the halteres, the remnants of the hind wings. It is a large order, containing an estimated 240,000 species, although under half...

     - Flies
  • Hymenoptera
    Hymenoptera
    Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees and ants. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and...

     - Ants, bees, sawflies and wasps
  • Lepidoptera
    Lepidoptera
    Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...

     - Butterflies and moths
  • Mecoptera
    Mecoptera
    Mecoptera are an order of insects with about 550 species in nine families worldwide. Mecoptera are sometimes called scorpionflies after their largest family, Panorpidae, in which the males have enlarged genitals that look similar to the stinger of a scorpion...

     - Scorpionflies
  • Megaloptera
    Megaloptera
    Megaloptera is an order of insects. It contains the alderflies, dobsonflies and fishflies, and there are about 300 known species.The Megaloptera were formerly considered part of a group then called Neuroptera, together with lacewings and snakeflies, but these are now generally considered to be...

     - Alderflies, dobsonflies and fishflies
  • Miomoptera
    Miomoptera
    Miomoptera is an extinct order of insects. Although it is thought to be a common ancestor of all holometabolous insects, because no smooth transition between Miomoptera and other holometabolous insect orders is known it is considered to be in a separate order unto itself.The Miomopterans were small...

     (extinct)
  • Neuroptera
    Neuroptera
    The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order contains some 6,010 species...

     - Lacewings, antlions, etc.
  • Protodiptera
    Protodiptera
    Protodiptera is an extinct order of insects containing the two genera Permotipula and Permila....

     (extinct)
  • Raphidioptera - Snakeflies
  • Siphonaptera - Fleas
  • Strepsiptera
    Strepsiptera
    The Strepsiptera are an order of insects with ten families making up about 600 species...

     - Twisted-winged parasites
  • Trichoptera
    Trichoptera
    The caddisflies are an order, Trichoptera, of insects with approximately 12,000 described species. Also called sedge-flies or rail-flies, they are small moth-like insects having two pairs of hairy membranous wings...

    - Caddisflies

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