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Ametabolism is a type of growth or life cycle in insects in which there is slight or no metamorphosis, only a gradual increase in size. It is present only in primitive wingless insects, e.g. order: Thysanura (Silverfish). [1] [2]

Silverfish species of insect

A silverfish is a small, wingless insect in the order Zygentoma. Its common name derives from the animal's silvery light grey colour, combined with the fish-like appearance of its movements. However, the scientific name, indicates the silverfish's diet consists of carbohydrates such as sugar or starches.


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Odonata order of insects

Odonata is an order of carnivorous insects, encompassing the dragonflies (Anisoptera) and the damselflies (Zygoptera). The Odonata form a clade, which has existed since the Permian.

Entomology scientific study of insects

Entomology is the scientific study of insects, a branch of zoology. In the past the term "insect" was more vague, and historically the definition of entomology included the study of terrestrial animals in other arthropod groups or other phyla, such as arachnids, myriapods, earthworms, land snails, and slugs. This wider meaning may still be encountered in informal use.

Diplura order of insects

The order Diplura is one of the four groups of hexapods, alongside insects, Collembola (springtails) and Protura. They are sometimes called "two-pronged bristletails". Around 800 species have been described, of which around 70 occur in North America, 12 in Great Britain and two in Australia.

Orthoptera order of insects (Insecta) including grasshoppers, crickets, weta and locusts

Orthoptera is an order of insects that comprises the grasshoppers, locusts and crickets, including closely related insects such as the katydids and wetas. The order is subdivided into two suborders: Caelifera – grasshoppers, locusts and close relatives; and Ensifera – crickets and close relatives.

Plecoptera order of insects

The Plecoptera are an order of insects, commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica. Stoneflies are believed to be one of the most primitive groups of Neoptera, with close relatives identified from the Carboniferous and Lower Permian geological periods, while true stoneflies are known from fossils only a bit younger. The modern diversity, however, apparently is of Mesozoic origin.

Pupa life stage of some insects undergoing transformation

A pupa is the life stage of some insects undergoing transformation between immature and mature stages. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, with four life stages: egg, larva, pupa, and imago. The processes of entering and completing the pupal stage are controlled by the insect's hormones, especially juvenile hormone, prothoracicotropic hormone, and ecdysone.

Rhizophoraceae family of plants

The Rhizophoraceae are a family of tropical or subtropical flowering plants. Among the better-known members are mangrove trees of the genus Rhizophora. Around 147 species are distributed in 15 genera, most native to the Old World. Some species produce wood, used for underwater construction or piling, and tannins for leather making.

Imago the last stage in an insects metamorphosis

In biology, the imago is the last stage an insect attains during its metamorphosis, its process of growth and development; it also is called the imaginal stage, the stage in which the insect attains maturity. It follows the final ecdysis of the immature instars.

Stinger organ

A stinger, or sting, is a sharp organ found in various animals capable of injecting venom, usually by piercing the epidermis of another animal.

Megaloptera order of insects

Megaloptera is an order of insects. It contains the alderflies, dobsonflies and fishflies, and there are about 300 known species.


Hemimetabolism or hemimetaboly, also called incomplete metamorphosis and paurometabolism, is the mode of development of certain insects that includes three distinct stages: the egg, nymph, and the adult stage, or imago. These groups go through gradual changes; there is no pupal stage. The nymph often somewhat resembles the adult stage but lacks wings and functional reproductive organs.

Megasecoptera is a paleozoic insect order. There are 22 known families of megasecopterans, with about 35 known genera.

Apterygota subclass of insects

The name Apterygota is sometimes applied to a subclass of small, agile insects, distinguished from other insects by their lack of wings in the present and in their evolutionary history; notable examples are the silverfish, the firebrat, and the jumping bristletails. Their first known occurrence in the fossil record is during the Devonian period, 417–354 million years ago.

Psocoptera order of insects

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 ψῶχος, psokhos meaning gnawed or rubbed and πτερά, ptera meaning wings. There are more than 5,500 species in 41 families in three suborders. Many of these species have only been described in recent years.

The Diaphanopterodea or Paramegasecoptera are an extinct order of moderate to large-sized Palaeozoic insects. They are first known from the Middle Carboniferous, and include some of the earliest known flying insects.

Apolysis The first process of molting, characterized by the detachment of the old cuticle from the underlying epidermal cells.

Apolysis is the separation of the cuticle from the epidermis in arthropods and related groups (Ecdysozoa). Since the cuticle of these animals is also the skeletal support of the body and is inelastic, it is shed during growth and a new covering of larger dimensions is formed. During this process, an arthropod becomes dormant for a period of time. Enzymes are secreted to digest the inner layers of the existing cuticle, detaching the animal from the outer cuticle. This allows the new cuticle to develop without being exposed to the environmental elements.

Entognatha class of arthropods

The Entognatha are a class of wingless (ametabolous) arthropods, which, together with the insects, makes up the subphylum Hexapoda. Their mouthparts are entognathous, meaning that they are retracted within the head. Entognatha are apterous, meaning that they lack wings. The class contains three orders: Collembola (springtails), Diplura and Protura, and over 5000 known species. These three groups were historically united with the now-obsolete order Thysanura to form the class Apterygota, but it has since been recognized that the hexapodous condition of these animals has evolved independently from that of insects, and independently within each order. The orders may not be closely related, in which case Entognatha would be a polyphyletic group.

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.

Monura is an extinct order of wingless insects in the subclass Apterygota. They resembled their modern relatives, the bristletails, and had a single lengthy filament projecting from the end of the abdomen. They also had a pair of leg-like cerci and some non-ambulatory abdominal appendages. The largest specimens reached 30 millimetres (1.2 in) or more, not counting the length of the filament.

Titanoptera order of insects

Titanoptera is an extinct order of neopteran insects from the Triassic period. Titanopterans were very large in comparison with modern insects, some having wingspans of up to 36 centimetres (14 in).


  1. McGavin, George C. Essential Entomology: An Order-by-Order Introduction. Oxford: Oxford University Press, 2001. pp. 20.
  2. Triplehorn, Charles A; Johnson, Norman F (2005). Borror and DeLong's introduction to the study of insects (7th ed.). Australia: Thomson, Brooks/Cole. ISBN   9780030968358.