Exopterygota
The Hemimetabola or Exopterygota provide an informal group within the insect, in which the young animal is often only by its magnitude from the adult animal, the imago is different. It is therefore contrary to the holometabolous insects ( Holometabola ) instead of no transformation through a pupal stage. The most striking difference between larva and adult are appearing only after the molt to the imago wings. Nomenclaturally correct the juvenile stage of hemimetabolic nymph is called if it has no independent formations that are missing the imago ( eg gills). Does it, however, such " Larvalorgane ", you should call it larva, as well as the young stages of the holometabolous insects. In actual usage, this difference is hardly ever so strictly observed, even in scientific publications is spoken, for example, of "locusts larvae ".
The hemimetabolic insects form a so-called paraphyletic taxon. This means that the holometabolous insects are not the sister group of the hemimetabolic insects, but have emerged from this. According to the current classification, the so-called Paraneoptera are ( these are the Hemiptera and the thrips within the hemimetabolic ) more closely related to the Holometabola than the hemimetabolic with each other would be (see Phylogenetic systematics of insects). In addition, the kinship group called Polyneoptera is also closely related with them than with the dragonflies or mayflies.
Paraphyletic taxa were in the classical taxonomy is not uncommon for the show further examples of how the " reptiles ". According to the currently prevailing in the taxonomy and systematics method of phylogenetic systematics ( cladistics or ), which goes back to the entomologist Willi Hennig, paraphyletic taxa are to be avoided because they obscure the actual relationships. Just like the term " reptiles " will continue to speak in the research of " hemimetabolic ", where the users are on the ratios is very clear. It is a practical, abbreviated term that is useful for sorting.
Occasionally, the term Heterometabola (or heterometabole insects) is used as the far-reaching Synonym ( excluding the urine sects ).
Animals that undergo no visible transformation, are sometimes referred to as ametabol, such as the little fish.
The following groups can be described as hemimetabol:
- Mayflies ( Ephemeroptera)
- Mantis ( Mantodea )
- Fishes ( Zygentoma )
- Thrips ( Thysanoptera ) or thrips
- Stick insects ( Phasmatodea )
- Gladiators ( Mantophasmatodea )
- Grasshopper ( caelifera )
- Ensifera ( Ensifera )
- Dragonflies ( Odonata )
- Cockroaches ( Blattodea )
- Hemiptera ( Hemiptera )
- Dust lice ( Psocoptera )
- Stoneflies ( Plecoptera )
- Tarsenspinner ( Embioptera )
- Termites ( Isoptera )
- Animal lice ( Phthiraptera )
- Cicadas ( Auchenorrhyncha )