Green hay horse ( Tettigonia viridissima ), female
|Olivier , 1789|
The locusts (Orthoptera) are an order of the insects (Insecta). They comprise more than 28,000 species and occur worldwide in all terrestrial habitats, with a few species also in freshwater. Some herbivorous ( phytophagous ) species have a tendency to mass reproduce and have been of great economic importance from ancient times until today.
The locusts are divided into two easily distinguishable groups, the long-feeler terrors (Ensifera) and the short-feeler terrors (Caelifera). The sister group relationship of these, and thus the monophyly of the taxon Orthoptera, has been disputed many times on the basis of morphological and molecular studies (see the section on systematics). Today, however, the overwhelming majority of studies indicate a relationship.
The expression "grasshopper" is already used in Old High German as hewiscrecko and goes back to the Old High German verb scare "(up) jump" back. The ability to jump as the most striking characteristic is also the inspiration for other names such as jumping horror, jumping cock, grasshopper, hayhopper or heugümper . In colloquial language, the term grasshopper is mainly used to describe representatives of the short-antennae terrors. The term grasshopper is not used quite so clearly for the representatives of the long-antennae terrors. Here representatives with a different physique are not always associated with locusts in common parlance. This applies in particular to the crickets (Grylloidea).
The scientific name Orthoptera comes from the Greek ὀρθός (orthos) straight and -πτερος (-pteros) winged. The name was originally given by Guillaume-Antoine Olivier for a more limited group which, in addition to the locusts, also included the cockroaches , the catching horrors and the ghosts . This grouping was summarized in German for a long time as "Geradflügler". According to current knowledge, the orders summarized in this way do not form a natural unit. For a long time, numerous scientists preferred the name Saltatoria Latreille , 1817, to distinguish it from the name and concept of the Geradflügler, but today it is considered a synonym .
The locusts are distinguished from related orders by the following common morphological features ( autapomorphies ):
- Construction of the pronotum : This is drawn down on the sides ("saddle-shaped"). It covers the pleuras , which are strongly regressed and deslerotized ("cryptopleuria").
- Construction of the hind legs: These are designed as jump legs. The thighs ( femora ) are enlarged to accommodate the jump muscles. The rails ( tibia ) are mostly rod-shaped. On the top they have two characteristic longitudinal rows of short thorns. There are locusts without jumping ability, but a secondary loss is assumed here (e.g. in the case of an underground way of life). Species from related orders sometimes have the ability to jump, but this has been achieved on a different anatomical basis.
- The foremost respiratory openings (spiracles) on the thorax are in two parts. Two outgoing tracheal trunks correspond to the transverse division .
- The wing systems of the nymphs (or larvae) are everted in the last two larval stages, so that the hind wings are on top.
- The base of the ovipositor is covered by an enlarged subgenital plate.
There are also numerous other similarities, but they are more difficult to interpret. They have in common with numerous related orders that the number of tarsal terms is always reduced, from originally five to mostly three or four. The cerci , appendages of the end of the abdomen, likewise consist of only a few limbs or only one limb.
The locust jump occurs through a jerky stretching of the joint between the femur and tibia. Field locusts such as the desert locust ( Schistocerca gregaria ) can jump a meter (with take-off speeds of 3.2 meters per second). Most leaf locusts are worse jumpers. But also the common shrub insect ( Pholidoptera griseoaptera ) can reach 66 centimeters, which is almost thirty times the body length. What is essential for the jump is the arrangement of the muscles with a greatly elongated extensor muscle, the lever arm of which is additionally extended by guiding the tendon over a button-like protrusion. In addition, the flexor and extensor muscles are excited simultaneously for a certain period, resulting in an explosive acceleration when the flexor relaxes. There are two types of jump mechanics:
- With most grasshoppers and crickets, the energy for the jump is mostly not stored by the muscle activity itself, but by the deformation of the exoskeleton , similar to a tensioned spring. As a result, the energy can be released suddenly when a locking mechanism is released. A large part of the spring force is usually stored in the deformation of a crescent-shaped sclerite near the joint.
- In most leaf locusts, the jump drive occurs predominantly through direct muscle contraction. In order to improve their jumping properties, they have particularly long rear legs.
Grasshoppers usually have relatively narrow forewings. The rear wings are enlarged at the rear to form a large anal fan or "Vannus" and thus reach a multiple of the area of the front wings. They contribute about three quarters of the buoyancy. The Vannus is spanned by longitudinal veins, similar to the rods of an umbrella, and stiffened by numerous transverse veins. Its surface is stiffened like corrugated cardboard by alternating high and low veins (corrugation). In the rest position it is folded in like a fan along these lines. The forewings of most grasshoppers are coarse and leather-like as cover wings ( Tegmina ), but there are groups with thin, membranous forewings. In many species, the space in front of the anterior marginal vein, the costa, is noticeably enlarged and forms a so-called precostal field (possible autapomorphy). In the resting position, the wings are usually carried like a roof over the abdomen, more rarely lying flat on the upper side.
During flight, both pairs of wings are moved independently of each other. The rear wings are arched on the downstroke, in contrast to other insect orders they are not rotated in the stroke and do not contribute anything to the lift on the upstroke. Due to the flight mechanism, many locusts are fast and persistent fliers, but they have little maneuverability.
Acoustic communication and sound generation
In most locusts, both Caelifera and Ensifera, the sexes are found through the singing of the male, which attracts the female. In order to be able to hear the generated sounds, they also have hearing organs, the tympanic organs , which, like vertebrate ears, can detect sound through the sound pressure, i.e. not only pick up the vibrations. Although they also use them differently, for example to recognize the location sounds of bats, this is their actual biological purpose. Both sound generation and hearing take place in both subordinates at different points and according to completely different principles, so that one has to assume convergence .
Are the Orthoptera an order?
The togetherness of the Caelifera and Ensifera has at times been strongly questioned , especially by an influential series of publications by the Canadian entomologist Keith Kevan . Some molecular studies also point in this direction. An examination of the wing joint makes it seem at least possible that the Ensifera closer to the stick insects were related (Phasmatodea) than with the Grasshopper. Today, however, the overwhelming number of researchers assume a monophyletic order Orthoptera. A togetherness has also been confirmed in numerous molecular studies (e.g.).
The grasshoppers belong to a family of morphologically relatively primitive insect orders, which is called Polyneoptera. The common feature of the orders summarized here are the rear wings, which are enlarged by a large anal fan, and the resulting similar flight style. Molecular studies (via homologous DNA sequences) also support their togetherness. The structure of the Polyneoptera is one of the most difficult problems in the systematics and phylogeny of insects, has not yet been conclusively clarified and is very controversial between various researchers. After morphological studies most often were stick insects (Phasmatodea) as a sister group called. The gladiators (Mantophasmatodea) and the cricket cockroaches (Grylloblattodea) are therefore considered to be closely related (both had historically been misinterpreted as locusts).
In molecular studies, this summary (sometimes referred to as Orthopterida, Orthopteroidea, or Orthoneoptera, to varying degrees) was not always supported. In most of the more recent studies there is evidence of an isolated position of the locusts, possibly with the other Polyneoptera as a sister group. Accordingly, the close relationship to the Phasmatodea, which has long been regarded as certain, does not exist in reality. However, these results are provisional and may change in more recent studies.
The division of the Orthoptera into the two suborders Ensifera and Caelifera and the monophyly of these two groups is almost indisputable today, if fossil forms from the Triassic or older are left out. A breakdown down to the family level could look like this (without groups known only from fossil fuels):
- Suborder long- probe horror (Ensifera) Chopard, 1920
- Superfamily Hagloidea Handlirsch, 1906
- Family Prophalangopsidae Kirby, 1906 (7 genera, 8 species)
- Superfamily Stenopelmatoidea Burmeister, 1838
- Superfamily Tettigonioidea Krauss, 1902
- Family Tettigoniidae Krauss, 1902 (1193 genera, 6827 species) ( deciduous locusts )
- Superfamily Rhaphidophoroidea Walker, 1871
- Family Rhaphidophoridae Walker, 1871 (77 genera, 497 species)
- Superfamily Schizodactyloidea Blanchard, 1845
- Family Schizodactylidae Blanchard, 1845 (2 genera, 15 species)
- Superfamily Grylloidea Laicharting, 1781
- Family Gryllidae Laicharting, 1781 (597 genera, 4664 species) ( Real crickets )
- Family Gryllotalpidae Leach, 1815 (6 genera, 100 species) ( mole crickets )
- Family Mogoplistidae Brunner von Wattenwyl, 1873 (30 genera, 365 species)
- Family Myrmecophilidae Saussure, 1874 (5 genera, 71 species) ( ant crickets )
- Superfamily Hagloidea Handlirsch, 1906
- Subordination of short-antenna terrors (Caelifera) Ander, 1936
- Superfamily Tridactyloidea Brullé, 1835
- Superfamily Tetrigoidea Serville, 1838
- Family Tetrigidae Serville, 1838 (221 genera, 1246 species) ( thorn terrors )
- Superfamily Eumastacoidea Burr, 1899
- Family Chorotypidae Stål, 1873 (43 genera, 160 species)
- Family Episactidae Burr, 1899 (18 genera, 64 species)
- Family Eumastacidae Burr, 1899 (47 genera, 230 species)
- Family Euschmidtiidae Rehn, 1948 (61 genera, 191 species)
- Family Mastacideidae Rehn, 1948 (2 genera, 10 species)
- Family Morabidae Rehn, 1948 (42 genera, 123 species)
- Family Proscopiidae Serville, 1838 (32 genera, 214 species)
- Family Thericleidae Burr, 1899 (57 genera, 220 species)
- Superfamily Trigonopterygoidea Walker, 1870
- Superfamily Tanaoceroidea Rehn, 1948
- Family Tanaoceridae Rehn, 1948 (2 genera, 3 species)
- Superfamily Pneumoroidea Blanchard, 1845
- Family Pneumoridae Blanchard, 1845 (9 genera, 17 species)
- Superfamily Pyrgomorphoidea Brunner von Wattenwyl, 1882
- Family Pyrgomorphidae Brunner von Wattenwyl, 1882 (143 genera, 455 species) ( cone-headed terrors )
- Superfamily Acridoidea MacLeay, 1821
- Family Acrididae MacLeay, 1821 (field locusts, 1380 genera, 6016 species)
- Family Charilaidae Dirsh, 1953 (4 genera, 5 species)
- Family Dericorythidae Jacobson & Bianchi, 1902–1905 (22 genera, 179 species)
- Family Lathiceridae Dirsh, 1954 (3 genera, 4 species)
- Family Lentulidae Dirsh, 1956 (11 genera, 35 species)
- Family Lithidiidae Dirsh, 1961 (4 genera, 13 species)
- Family Ommexechidae Bolívar, 1884 (13 genera, 33 species)
- Family Pamphagidae Burmeister, 1840 (94 genera, 448 species)
- Family Pyrgacrididae Kevan, 1974 (1 genus, 2 species)
- Family Romaleidae Brunner von Wattenwyl, 1893 (111 genera, 465 species)
- Family Tristiridae Rehn, 1906 (18 genera, 25 species)
Way of life
In all grasshoppers, fertilization takes place through the transfer of a sperm packet ( spermatophore ) from the male to the female. In the case of the Caelifera such as the field locusts (Acrididae), the spermatophore is applied internally by means of a more or less complex copulation apparatus ( aedeagus ). When the partners separate, the spermatophore breaks open, the tubular part gets stuck in the female genital tract. Until it has been resorbed, this tube prevents further attempts at mating by competitors. In some groups (Acrididae: Catantopinae, Melanoplinae) the Aedeagus has a complex structure and is species-specific, but in many others it is very similar and hardly distinguishable between species. An aedeagus is missing in the Ensifera such as the grasshopper and crickets. The male applies a large spermatophore on the outside. This usually contains a large part of the appendix (spermatophylax), which is rich in nutrients but free of sperm. This large spermatophore not only competes between the males, but also provides valuable nutrients that increase the reproductive success of the female.
The Ensifera use their long ovipositor to sink eggs either in the ground or in soft plant tissue. In the Caelifera, the ovipositor is secondary, one of the three pairs of valves has receded except for rudiments. The other two form loose flaps. They usually serve as digging tools when laying eggs in the ground. In some species, the eggs are instead laid on plants, but then always on the surface.
Most grasshoppers lay their eggs individually or in loose, small clusters. The species of the superfamily Acridoidea (field locusts and relatives) wrap them in an ootheca . This consists of a foamy secretion that often later hardens. The ootheca can be glued to the ground or parts of plants and thus additionally camouflaged.
Locust nymphs are similar to adults in their body shape, and usually also in their way of life. Grasshoppers are hemimetabolic insects , they do not pupate. Usually nymphs and adults are common in the same habitat and have identical or similar food preferences. Wing systems and body appendages such as oviposers and cerci are present from the first nymph stage, so that it is not always easy to v. a. in short-winged species to differentiate nymphs from adults.
In all grasshoppers, a worm-shaped (“vermiform”) first stage (prolarve) hatches from the egg, which sheds its skin immediately (or after leaving the ootheca) to the first nymph stage. The number of nymph stages is variable between the species, it can also be variable within the same species depending on the length of the day, living conditions and sex. Most grasshoppers have 4, 5 or 6 nymph stages (maximum 10), with leafy grasshoppers and crickets it is usually 5 to 9 with Wetas 7 to 11. The maximum number measured here is 14 (for house crickets ( Acheta domesticus ) under unfavorable living conditions) .
Most locust species have one generation per year ( monovoltine ). Few species have two or more generations in the same year, or it takes a generation two years to complete the life cycle.
One in four of the more than 1000 locust species native to Europe is considered an endangered species . The most important sources of risk include the intensification of agriculture, the increasing number of fires in the Mediterranean area, as well as urbanization and the tourist development of coasts and mountains. The endangerment of many species of locusts is also a result of their occasionally extremely small distribution areas: Many species only occur on individual islands or on small mountain slopes; any change in land use on such small areas can therefore quickly lead to the extinction of species.
Grasshoppers have powerful mandibles, which are essential for food production in all species. The mandibles of almost all types are asymmetrical (left and right mandibles are different) and slightly overlap in the rest position. As with many insects, the mandible consists of a front, mostly toothed incisive edge (incisive) and a widened cheek (molar region, mola) behind it for grinding the food. Depending on the type of diet and preferred food, the structure of the mandibles (subordinate to the other mouthparts ) is modified. A distinction is made between a graminivorous type (grasses), a herbivorous or forbivorous type (herbs), a graminivorous-herbivorous or ambivorous type (both), an omnivorous type (herbivores and predators) and a carnivorous type (predators). Some investigators differentiate between further types and subtypes.
Many species are actually not very specialized in the type of food they eat ( omnivorous ), both in food choice experiments in the laboratory and after field observations and analysis of food residues in the crop or in the faeces, they accept both animal and vegetable food in varying proportions. Among the herbivorous (phytophagous) insects, the locusts are an exception: They are the only group in which the majority of the species are polyphagous, i.e. that is, that they accept food plants from more than one family. In the other groups it is usually less than a quarter of the species. On closer examination, however, clear preferences can be seen in various species and groups of species, even if the animals, e.g. B. in times of need with a lack of food, accept other things as an exception. The actual " grasshoppers " (Acrididae: Gomphocerinae) actually feed almost exclusively on sweet grasses . Species of the subfamily Melanoplinae, on the other hand, prefer herbaceous plants, as do numerous leaf locusts and crickets. Species with preferred habitats with little vegetation, such as many thorn terrors (Tetrigidae) and wasteland terrors (Acrididae: Oedipodinae) living in rocky heaths or sandy corridors, feed to a large extent on algae, lichens and mosses. Although many species live in tree canopies, relatively few specialize in leaves from deciduous trees. However, outside of Europe and North America, the biology of most species (with the exception of some agricultural pests) is largely unknown.
Locusts for food
Grasshoppers are traditionally eaten in parts of Africa , Asia and South America as a protein-rich food. Usually they are fried or grilled for preparation. In Judaism , locusts are kosher , with restrictions depending on their religion . The Arabic cuisine (for example in Yemen ) knows grasshoppers as a starter. In Cambodia , larger specimens are filled with peanuts and briefly fried in a wok over high heat . Locusts were also eaten in the ancient Orient.
In Switzerland , a species of locust, the European migratory locust ( Locusta migratoria ), has been approved as a food since May 1, 2017 . These locusts can, under certain conditions, be given to consumers as whole animals, shredded or ground.
Many keepers of terrarium animals (especially reptiles ) breed their animals' live food themselves. Migratory locusts and desert locusts are the main food of carnivorous house reptiles alongside crickets , cockroaches and mealworms . Migratory locusts are preferred, as desert locusts can climb up the glass walls of the terrariums.
Migratory locusts are kept in a well-ventilated terrarium from which the animals cannot escape. They are fed with wheat seedlings, soy seedlings, hay, salads or grass. The green fodder must be insecticide-free and must not be contaminated with fungi and roundworms ; both can harm locusts. A diet rich in protein helps keep animals healthy. The locusts are fed daily.
Migratory locusts are well suited as food animals, as locusts of all ages (from a few millimeters to six centimeters in size) are available for feeding, but the size of the live food must be adapted to the reptiles. The attitude is noiseless and odorless and the workload is small. The propagation can be stopped by cooling the cultivation container below 30 ° C. Locusts that are released in the terrarium and not eaten by the reptiles can cause damage to the vegetation.
A total of 12 species of grasshopper are known as migratory locusts . Even in prehistoric times, human settlements were haunted by voracious swarms of migratory locusts. In Europe around 400 incursions are estimated for the Middle Ages , for example 1338 and 1408. One of the earliest representations, an Egyptian tomb painting from the 15th century BC. BC, shows a grasshopper on a papyrus flower. Starting with the Egyptian plague , which is described in the 2nd book of Moses (Exodus), locusts are mentioned 30 times in the Bible alone. The Aztecs were also familiar with the insects long before the Europeans arrived.
One of the largest ever documented flocks of locusts settled in South Africa in 1784. At that time, over 300 billion insects covered an estimated 3,000 km² of land. Around 600,000 tons of plants per day fell victim to their greed. The wind drove the school out to sea. The dead insects were washed ashore with the tide. They piled up on the beach for a length of 80 kilometers over a meter high.
The rock hideaway ( Melanoplus spretus ), which infested the American Midwest in the 19th century with the largest ever documented swarms, died out around the turn of the 20th century, because no living specimen has been seen since 1902. But other species of locusts are still regularly destroying crops in Africa, Asia, South America and Australia and destroying the livelihood of people. Today swarms of locusts are usually fought with the help of insecticides .
The largest locusts in southern Germany lived in the Jura around 150 million years ago in the Eichstätt area in Bavaria. This is the genus Pycnophlebia with wings up to 15 centimeters long. The weta with a body length of up to 9 cm are among the largest still living locusts .
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