Tegmen

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Left tegmen of male Blatta orientalis Blatta orientalis male from Botevgrad, Bulgaria 03.jpg
Left tegmen of male Blatta orientalis
Lithoblatta lithophila, a Jurassic fossil, some 200 million years more recent than the emergence of cockroaches in the Carboniferous. Even the earliest cockroaches had tegmina that fossilised well. Lithoblatta lithophila.jpg
Lithoblatta lithophila, a Jurassic fossil, some 200 million years more recent than the emergence of cockroaches in the Carboniferous. Even the earliest cockroaches had tegmina that fossilised well.

A tegmen (PL: tegmina) designates the modified leathery front wing on an insect particularly in the orders Dermaptera (earwigs), Orthoptera (grasshoppers, crickets and similar families), Mantodea (praying mantis), Phasmatodea (stick and leaf insects) and Blattodea (cockroaches). [1]

Contents

It is also a term used in botany to describe the delicate inner protective layer of a seed, [2] and in zoology to describe a stiff membrane on the upper surface of the crown of a crinoid. [3]

In vertebrate anatomy it denotes a plate of thin bone forming the roof of the middle ear. [2]

The nature of tegmina

Earwig wing anatomy. One tegmen opened, the other removed to show wing folding mechanism. Earwig wing cutted.png
Earwig wing anatomy. One tegmen opened, the other removed to show wing folding mechanism.

The term tegmen refers to a miscellaneous and arbitrary group of organs in various orders of insects; they certainly are homologous in the sense that they all are derived from insect forewings, but in other senses they are analogous; for example, the evolutionary development of the short elytra of the Dermaptera shared none of the history of the development of tegmina in the Orthoptera, say. Also, in some other insects fore- and hindwings differ both in texture and their role in flight, but are not universally regarded as tegmina. For example, the hemelytra of some Hemiptera have been called tegmina by some authorities, [4] but not by most modern authors.

Entomologists do not customarily refer to the forewing of a beetle as a tegmen; the term for beetles' forewings is elytra .

The function of tegmina

Note the camouflage-adapted anatomy of the tegmina of the middle specimen DruryV1P050AA.jpg
Note the camouflage-adapted anatomy of the tegmina of the middle specimen
Stagmatoptera supplicaria, drawing showing eye-marks on tegmina. Stagmatoptera supplicaria MHNT femelle vol.jpg
Stagmatoptera supplicaria, drawing showing eye-marks on tegmina.

Probably the major role of tegmina in general is that of protecting the hindwings when folded. In many insects they also are important in camouflage and in displays, especially defensive display, where the tegmina are drab, but cover aposematic displays that are startling when suddenly uncovered. Sometimes, as in some mantids, the tegmina crossed over the back are not striking, but when suddenly raised, act as a threatening display resembling a pair of eyes.

Tegmina do not play a major active, flapping role in flying, though they are aerodynamically significant in insects such as migratory locusts that fly vigorously for long distances. This is probably the main justification for distinguishing between say, the forewings of cockroaches, which are called tegmina, and the forewings of some Neuroptera, which though stiffer than the rear wings, are flapped in flight.

Tegmina and sound

"Song" of Gryllus
pennsylvanicus

Tegmina, generally being stiffer than the rear wings, are used as sound boards by many species of insects, especially Orthoptera; in many locusts they make a crackling noise in flight, and in many crickets, tree crickets, and even mole crickets, the tegmina have undergone marked anatomical adaptations, often asymmetric, for sound production.

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<span class="mw-page-title-main">Tettigoniidae</span> Family of insects

Insects in the family Tettigoniidae are commonly called katydids, or bush crickets. They have previously been known as "long-horned grasshoppers". More than 8,000 species are known. Part of the suborder Ensifera, the Tettigoniidae are the only extant (living) family in the superfamily Tettigonioidea.

<span class="mw-page-title-main">Orthoptera</span> Order of insects including grasshoppers, crickets, wētā and locusts

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

<span class="mw-page-title-main">Earwig</span> Order of insects

Earwigs make up the insect order Dermaptera. With about 2,000 species in 12 families, they are one of the smaller insect orders. Earwigs have characteristic cerci, a pair of forcep-like pincers on their abdomen, and membranous wings folded underneath short, rarely used forewings, hence the scientific order name, "skin wings". Some groups are tiny parasites on mammals and lack the typical pincers. Earwigs are found on all continents except Antarctica.

<span class="mw-page-title-main">Elytron</span> Hardened insect forewing

An elytron is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra, and in most species only the basal half is thickened while the apex is membranous, but when they are entirely thickened the condition is referred to as "coleopteroid". An elytron is sometimes also referred to as a shard.

<span class="mw-page-title-main">Cercus</span> Paired appendages on the rear-most segments of many arthropods

Cerci are paired appendages on the rear-most segments of many arthropods, including insects and symphylans. Many forms of cerci serve as sensory organs, but some serve as pinching weapons or as organs of copulation. In many insects, they simply may be functionless vestigial structures.

<span class="mw-page-title-main">Mole cricket</span> Members of the insect family Gryllotalpidae

Mole crickets are members of the insect family Gryllotalpidae, in the order Orthoptera. Mole crickets are cylindrical-bodied, fossorial insects about 3–5 cm (1.2–2.0 in) long as adults, with small eyes and shovel-like fore limbs highly developed for burrowing. They are present in many parts of the world and where they have arrived in new regions, may become agricultural pests.

<span class="mw-page-title-main">Grasshopper</span> Common name for a group of insects

Grasshoppers are a group of insects belonging to the suborder Caelifera. They are among what is possibly the most ancient living group of chewing herbivorous insects, dating back to the early Triassic around 250 million years ago.

<span class="mw-page-title-main">Hemimetabolism</span>

Hemimetabolism or hemimetaboly, also called partial 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 has a thin exoskeleton and resembles the adult stage but lacks wings and functional reproductive organs. The hemimetabolous insects differ from ametabolous taxa in that the one and only adult instar undergoes no further moulting.

<i>Parcoblatta fulvescens</i> Species of cockroach

Parcoblatta fulvescens, the fulvous wood cockroach, is a species of cockroach endemic to the United States and possibly Canada that measures around 13 mm (0.5 in) long.

<span class="mw-page-title-main">Caelifera</span> Suborder of insects

The Caelifera are a suborder of orthopteran insects. They include the grasshoppers and grasshopper-like insects, as well as other superfamilies classified with them: the ground-hoppers (Tetrigoidea) and pygmy mole crickets (Tridactyloidea). The latter should not be confused with the mole crickets (Gryllotalpidae), which belong to the other Orthopteran sub-order Ensifera.

<span class="mw-page-title-main">Insect wing</span> Body part used by insects to fly

Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments, and the two pairs are often referred to as the forewings and hindwings, respectively, though a few insects lack hindwings, even rudiments. The wings are strengthened by a number of longitudinal veins, which often have cross-connections that form closed "cells" in the membrane. The patterns resulting from the fusion and cross-connection of the wing veins are often diagnostic for different evolutionary lineages and can be used for identification to the family or even genus level in many orders of insects.

Orthopteroids are insects which historically would have been included in the order Orthoptera and now may be placed in the Polyneoptera. When Carl Linnaeus started applying binomial names to animals in the 10th edition of his Systema Naturae in 1758, there were few animals included in the scheme, and consequently few groups. As more and more new species were discovered and differences recognised, the original groups proposed by Linnaeus were split up.

<span class="mw-page-title-main">Jerusalem cricket</span> Type of cricket-like animals

Jerusalem crickets are a group of large, flightless insects in the genera Ammopelmatus and Stenopelmatus, together comprising the tribe Stenopelmatini. The former genus is native to the western United States and parts of Mexico, while the latter genus is from Central America.

<span class="mw-page-title-main">Cricket (insect)</span> Small insects of the family Gryllidae

Crickets are orthopteran insects which are related to bush crickets, and, more distantly, to grasshoppers. In older literature, such as Imms, "crickets" were placed at the family level, but contemporary authorities including Otte now place them in the superfamily Grylloidea. The word has been used in combination to describe more distantly related taxa in the suborder Ensifera, such as king crickets and mole crickets.

<span class="mw-page-title-main">Insect morphology</span> Description of the physical form of insects

Insect morphology is the study and description of the physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insects from other arthropods: they have a body divided into three regions, three pairs of legs, and mouthparts located outside of the head capsule. This position of the mouthparts divides them from their closest relatives, the non-insect hexapods, which include Protura, Diplura, and Collembola.

<span class="mw-page-title-main">Tridactylidae</span> Family of Caelifera

The Tridactylidae are a family in the insect order Orthoptera. They are small, mole-cricket-like insects, almost always less than 20 mm (0.79 in) long when mature. Generally they are shiny, dark or black, sometimes variegated or sandy-coloured. They commonly live in short tunnels and are commonly known as pygmy mole crickets, though they are not closely related to the true "mole crickets" (Ensifera), as they are included in the Caelifera suborder.

Panoploscelis is a genus of very large insects belonging to the true katydid tribe Eucocconotini, which is a subfamily of the Tettigoniidae. Like the other members of the suborder Ensifera, Panoploscelis are part of the insect order Orthoptera, which also contains crickets, grasshoppers and locusts. Members of this genus are among the largest katydids of the Neotropics.

<i>Cariblatta lutea</i> Species of cockroach

Cariblatta lutea is a small species of cockroach native to the United States and other countries, measuring usually around 7 millimeters long as an adult and under 2 millimeters from head tip to abdomen tip at the 1st instar or hatchling. It consists of two subspecies, the small yellow cockroach, and the least yellow cockroach.

<i>Parcoblatta bolliana</i> Species of cockroach

Parcoblatta bolliana, Boll's wood cockroach or Boll's wood roach, is a small species of wood cockroach native to the United States, measuring around 11 mm (0.43 in) long.

<span class="mw-page-title-main">Polyneoptera</span> Group of insects

The cohort Polyneoptera is a proposed taxonomic ranking for the Orthoptera and all other Neopteran insects believed to be more closely related to Orthoptera than to any other insect orders. These winged insects, now in the Paraneoptera, were formerly grouped as the Hemimetabola or Exopterygota on the grounds that they have no metamorphosis, the wings gradually developing externally throughout the nymphal stages.

References

  1. Richards, O. W.; Davies, R.G. (1977). Imms' General Textbook of Entomology: Volume 1: Structure, Physiology and Development Volume 2: Classification and Biology. Berlin: Springer. ISBN   0-412-61390-5.
  2. 1 2 "tegmen | Definition of tegmen in English by Oxford Dictionaries". Oxford Dictionaries | English. Archived from the original on November 13, 2018. Retrieved 2018-11-12.
  3. O'Hara, Timothy; Byrne, Maria (2017). Australian Echinoderms: Biology, Ecology and Evolution. Csiro Publishing. p. 171. ISBN   978-1-4863-0763-0.
  4. Gordh, Gordon (2001). A Dictionary of Entomology. Wallingford: CABI Pub. ISBN   978-0-85199-291-4.