Exopterygota

Exopterygota

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The Exopterygota, also known as Hemipterodea, are a superorder of insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s of the subclass
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 Pterygota
Pterygota
Pterygota is a subclass of insects that includes the winged insects. It also includes insect orders that are secondarily wingless ....

 in the infraclass Neoptera
Neoptera
Neoptera is a classification group that includes almost all the winged insects, specifically those that can flex their wings over their abdomens...

, in which the young resemble adults but have externally-developing wings. They undergo a modest change between immature and adult, without going through 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...

l stage. The nymphs develop gradually into adults through a process of moulting
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...

.

The Exopterygota are a highly diverse insect superorder, with at least 130,000 living species divided between 15 orders
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

. They include termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...

s, locust
Locust
Locusts are the swarming phase of short-horned grasshoppers of the family Acrididae. These are species that can breed rapidly under suitable conditions and subsequently become gregarious and migratory...

s, thrips, lice and stick insects, among many other types of insects.

They are distinguished from 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...

 (or Holometabola) by the way in which their wings develop. Endopterygota (meaning literally "internal winged forms") develop wings inside the body and undergo an elaborate metamorphosis involving a pupal stage. Exopterygota ("external winged forms") develop wings on the outside of their bodies without going through a true pupal stage, though a few have something resembling a pupa (e.g., Aleyrodidae).

Ephemeroptera (mayflies) and Odonata
Odonata
Odonata is an order of insects, encompassing dragonflies and damselflies . The word dragonfly is also sometimes used to refer to all Odonata, but the back-formation odonate is a more correct English name for the group as a whole...

 (dragonflies and damselflies) also have gradual wing development, this being a plesiomorphic trait. These two orders belong to the paraphyletic infraclass Palaeoptera however, which is not included in Neoptera. As opposed to Neoptera, they cannot fold their wings over their back in the horizontal plane
Horizontal plane
In geometry, physics, astronomy, geography, and related sciences, a plane is said to be horizontal at a given point if it is perpendicular to the gradient of the gravity field at that point— in other words, if apparent gravity makes a plumb bob hang perpendicular to the plane at that point.In...

, only vertically (as damselflies do) if at all.

Systematics


ITIS
Integrated Taxonomic Information System
The Integrated Taxonomic Information System is a partnership designed to provide consistent and reliable information on the taxonomy of biological species. ITIS was originally formed in 1996 as an interagency group within the U.S...

 considers any subdivision of the Neoptera beyond the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

s invalid, but this is almost universally rejected.

More recently, there is increasing debate about how to subdivide the Exopterygota, and the Neoptera in general. It is realized that some presumed Exopterygota may in fact be basal neopterans, making the superorder paraphyletic, just as the Palaeoptera are now increasingly accepted to be among the winged insects in general.

Here is a complete list of living and Extinct orders of "exopterygotes", with some proposed subdivisions:

Superorder Exopterygota sensu stricto
  • Caloneurodea (Extinct)
  • Titanoptera
    Titanoptera
    The Titanoptera are an extinct order of insects from the Triassic period. They were very large by comparison with modern insects, some having wingspans of up to ....

     (Extinct)
  • Protorthoptera
    Protorthoptera
    The Protorthoptera are an extinct order of Palaeozoic insects, and represent a wastebasket taxon and paraphyletic assemblage of basal neoptera. They appear during the Middle Carboniferous , making them among the earliest known winged insects in the fossil record. Pronotal lobes may be expanded to...

     (Extinct)
  • Plecoptera
    Plecoptera
    Plecoptera are an order of insects, commonly known as stoneflies. There are some 3,500 described species worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica...

     (stoneflies)
  • Embioptera
    Embioptera
    The order Embioptera, commonly known as webspinners, are a small group of mostly tropical and subtropical insects, classified under the subclass Pterygota. The order has also been referred to as Embiodea or Embiidina...

     (webspinners)
  • Zoraptera
    Zoraptera
    The insect order Zoraptera contains a single family, the Zorotypidae, which in turn contains one extant genus with 34 species, Zorotypus as well as 9 extinct species.-Phylogeny:...

     (angel insects)
  • Dermaptera (earwigs)
  • Orthoptera
    Orthoptera
    Orthoptera is an order of insects with paurometabolous or incomplete metamorphosis, including the grasshoppers, crickets and locusts.Many insects in this order produce sound by rubbing their wings against each other or their legs, the wings or legs containing rows of corrugated bumps...

     (grasshopper
    Grasshopper
    The grasshopper is an insect of the suborder Caelifera in the order Orthoptera. To distinguish it from bush crickets or katydids, it is sometimes referred to as the short-horned grasshopper...

    s, etc.)

Proposed superorder Dictyoptera
Dictyoptera
Dictyoptera includes three groups of polyneopterous insects - cockroaches , termites and mantids...

  • Phasmatodea
    Phasmatodea
    The Phasmatodea are an order of insects, whose members are variously known as stick insects , walking sticks or stick-bugs , phasmids, ghost insects and leaf insects...

     (stick insects - tentatively placed here)
  • Notoptera
    Notoptera
    The insect order Notoptera, a group first proposed in 1915, has been largely unused since its original conception, but in the most recent classification of the lineage of insects that includes the Grylloblattodea and Mantophasmatodea, the name was resurrected and redefined so as to give a single...

     (ice-crawlers & gladiators - tentatively placed here)
  • Blattaria (cockroaches)
  • Isoptera (termites)
  • Mantodea (mantids)

Proposed superorder Paraneoptera
Paraneoptera
Paraneoptera is a monophyletic superorder of insects which includes four orders, the bark lice, true lice, thrips, and hemipterans, the true bugs. The mouthparts of the Paraneoptera reflect diverse feeding habits...

  • Psocoptera
    Psocoptera
    Psocoptera are an order of insects that are commonly known as booklice, barklice or barkflies. They first appeared in the Permian period, 295–248 million years ago. They are often regarded as the most primitive of the hemipteroids. Their name originates from the Greek word psokos meaning...

     (booklice, barklice)
  • Thysanoptera (thrips)
  • Phthiraptera (lice)
  • Hemiptera
    Hemiptera
    Hemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...

    (true bugs)