Temporal range: Late Permian–Recent
Grasshoppers are Orthopteran insects of the suborder Caelifera. They are sometimes referred to as short-horned grasshoppers to distinguish them from the katydids (bush crickets). Grasshopper species which change colour and behaviour at high population densities are called locusts.
- 1 Characteristics
- 2 Diversity and range
- 3 Biology
- 4 Reproduction
- 5 Predators, parasites and pathogens
- 6 Relationship with humans
- 7 See also
- 8 References
- 9 Sources
- 10 External links
Grasshoppers have antennae that are generally shorter than their body and short ovipositors. They also have pinchers or mandibles that cut and tear off food. Those species that make easily heard noises usually do so by rubbing the hind femurs against the forewings or abdomen (stridulation), or by snapping the wings in flight. Tympana, if present, are on the sides of the first abdominal segment. The hind femora are typically long and strong, fitted for leaping. Generally they are winged: the hind wings are membranous while the front wings (tegmina) are thickened and not fit for flight. Females are normally larger than males, with short ovipositors. Males have a single unpaired plate at the end of the abdomen. Females have two pairs of valves (triangles) at the end of the abdomen used to dig in sand during egg laying.
Grasshoppers are easily confused with the other sub-order of Orthoptera, Ensifera (crickets), but differ in many aspects, such as the number of segments in their antennae and structure of the ovipositor, as well as the location of the tympana and modes of sound production. Ensiferans have antennae with at least 20–24 segments, and caeliferans have fewer. In evolutionary terms, the split between the Caelifera and the Ensifera is no more recent than the Permo-Triassic boundary (Zeuner 1939).
Diversity and range
Some 2,400 valid Caeliferan genera and about 11,000 valid species have been described to date. Many undescribed species exist, especially in tropical wet forests. The Caelifera are predominantly tropical with fewer species in temperate zones.
Diet and digestion
Grasshoppers prefer to eat grasses, leaves and cereal crops, but many species are omnivorous. Most grasshoppers are polyphagous, eating from multiple host plants. The mandibles chew food very slightly and start mechanical digestion. Salivary glands in the buccal cavity chemically digest the carbohydrates in the grasses and similar foods they eat. The gizzard has tooth-like features which grind the food further. From there, food enters the stomach, wheredigestive enzymes mix with the food to break it down. Waste products consist mainly of uric acid, urea and amino acids, and are expelled as dry pellets.
The salivary glands and midgut secrete digestive enzymes. The midgut secretes protease, lipase, amylase, and invertase, among other enzymes. The particular ones secreted vary with the different diets of grasshoppers.
Grasshoppers have a typical insect nervous system. There is a central nervous system that consists of a ventral nerve cord containing a chain of ganglia, connected together longitudinally by bilaterally-paired bundles of axons. In general there is one ganglion per segment. The ganglion at the front of the body forms the brain, with enhanced neural machinery for processing sensory information from the eyes and antennae. There is also a series of small ganglia known as the visceral nervous system; these control a functions of the gut, respiratory and hormonal systems.
Grasshoppers have an extensive set of external sense organs. On the head there are a pair of large compound eyes and three simple eyes (ocelli), a pair of antennae containing olfactory (smell) and touch receptors, and mouthparts containing gustatory (taste) receptors. At the front end of the abdomen there is a pair of tympanal organs for sound reception. There are numerous fine hairs covering the whole body that act as mechanoreceptors (touch and wind sensors), and these are most dense on the antennae, palps (part of the mouth), and cerci (near the posterior). There are special receptors (campaniform sensillae) embedded in the cuticle that sense pressure and cuticle distortion. There are internal "chordotonal" sense organs specialized to detect position and movement about the joints of the exoskeleton. The receptors convey information to the CNS through sensory neurons, and most of these have their cell bodies located in the periphery near the receptor site itself.
Circulation and respiration
Like other insects, grasshoppers have open circulatory systems with their body cavities filled with hemolymph. The dorsal vessel is the exception to the grasshopper's open circulation; it is a tube which extends from the head through the thorax to the abdomen. The part in the abdomen is the heart; the aorta extends from the heart to the head through the thorax. Haemolymph is pumped forward from the hind end and the sides of the body through a series of valved chambers, each of which contains a pair of lateral openings (ostia), and is discharged in the head. Accessory pumps carry haemolymph through the wing veins and along the legs and antennae before it flows back to the abdomen. The haemolymph circulates nutrients through the body and carries metabolic wastes to the malphighian tubes to be excreted.
Respiration is performed using tracheae, air-filled tubes, which open at the surfaces of the thorax and abdomen through pairs of spiracles. The spiracle valves only open to allow oxygen and carbon dioxide exchange. The tracheoles, found at the end of the tracheal tubes, are insinuated between cells and carry oxygen throughout the body.
Grasshoppers jump by extending their large back legs and pushing against the substrate (the ground, a twig, a blade of grass or whatever else they are standing on); the reaction force propels them into the air. They jump for several reasons; to escape from a predator, to launch themselves for flight, or simply to move from place to place. For the escape jump in particular there is strong selective pressure to maximize take-off velocity, since this determines the range. This means that the legs must thrust against the ground with both high force and a high velocity of movement. However, a fundamental property of muscle is that it cannot contract with both high force and high velocity, which seems like a problem. Grasshoppers overcome this apparent contradiction by using a catapult mechanism to amplify the mechanical power produced by their muscles.
The jump is a three-stage process. First, the grasshopper fully flexes the lower part of the leg (tibia) against the upper part (femur) by activating the flexor tibiae muscle (the back legs of the immature grasshopper in the top photograph are in this preparatory position). Second, there is a period of co-contraction in which force builds up in the large, pennate extensor tibiae muscle, but the tibia is kept flexed by the simultaneous contraction of the flexor tibiae muscle. The extensor muscle is much stronger than the flexor muscle, but the latter is aided by specializations in the joint that give it a large effective mechanical advantage over the former when the tibia is fully flexed. Co-contraction can last for up to half a second, and during this period the extensor muscle shortens and stores elastic strain energy by distorting stiff cuticular structures in the leg. The extensor muscle contraction is quite slow (almost isometric), which allows it to develop high force (up to 14 N in the desert locust), but because it is slow only low power is needed. The third stage of the jump is the trigger relaxation of the flexor muscle, which releases the tibia from the flexed position. The subsequent rapid tibial extension is driven mainly by the relaxation of the elastic structures, rather than by further shortening of the extensor muscle. In this way the stiff cuticle acts like the elastic of a catapult, or the bow of a bow-and-arrow. Energy is put into the store at low power by slow but strong muscle contraction, and retrieved from the store at high power by rapid relaxation of the mechanical elastic structures.
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Predators, parasites and pathogens
Grasshoppers have many predators, including ants such as Crematogaster.
Spinochordodes tellinii and Paragordius tricuspidatus are parasitic worms that infect grasshoppers and alter the behaviour of their hosts. The grasshopper is persuaded to leap into a nearby body of water where it drowns, thus enabling the parasite to continue with the next stage of its life cycle which takes place in water. The grasshopper nematode (Mermis nigrescens) is a long slender worm that infests grasshoppers, living in the insect's hemocoel. Adult worms lay eggs on plants and the host gets infected when it eats the foliage.
Grasshoppers are affected by diseases caused by bacteria, viruses, fungi and protozoa. The bacteria Serratia marcescens and Pseudomonas aeruginosa have both been implicated in causing disease in grasshoppers, as has the entomopathogenic fungus Beauveria bassiana. This widespread fungus has been used to control various pest insects around the world, but although it infects grasshoppers, basking in the sun has the result of raising the insect's temperature above a threshold tolerated by the fungus, and the infection is not lethal. The fungal pathogen Entomophaga grylli is able to influence the behaviour of its grasshopper host, causing it to climb to the top of a plant and cling to the stem as it dies. This ensures wide dispersal of the fungal spores liberated from the corpse.
The fungal pathogen Metarhizium acridum is found in Africa, Australia and Brazil where it has caused epizootics in grasshoppers. It is being investigated for possible use as a microbial insecticide for locust control. The microsporidian fungus Nosema locustae, once thought to be a protozoan, can be lethal to grasshoppers. It has to be consumed by mouth and is the basis for a bait-based commercial microbial pesticide. Various other microsporidians and protozoans are found in the gut.
Grasshoppers are often camouflaged to avoid detection by predators that hunt by sight. Their coloration usually resembles the background, whether green for leafy vegetation, sandy for open areas or grey for rocks. Some species can change their coloration to suit their surroundings.
Grasshoppers often have deimatic patterns on their wings, giving a sudden flash of bright colours that may startle predators long enough to give time to escape in a combination of jump and flight.
Some species may be genuinely aposematic, having both bright warning coloration and sufficient toxicity to dissuade predators. Dictyophorus productus is a "heavy, bloated, sluggish insect" that makes no attempt to hide; it has a bright red abdomen. A Cercopithecus monkey that ate other grasshoppers refused to eat the species.
Relationship with humans
In certain countries, grasshoppers are eaten as a good source of protein. In southern Mexico, chapulines are prized for their high content of protein, minerals and vitamins. They are usually collected at dusk, using lamps or electric lighting, in sweep nets. Sometimes they are placed in water for 24 hours, after which they can be boiled or eaten raw, sun-dried, fried, flavoured with spices, such as garlic, onions, chile, drenched in lime, and used in soup or as a filling for various dishes. They are abundant in Central and Southern Mexican food and street markets.
In some countries in the Middle East, grasshoppers are boiled in hot water with salt, left in the sun to dry then eaten as snacks.
Locusts are several species of short-horned grasshoppers of the family Acrididae that sometimes form very large groups (swarms); these can be highly destructive and migrate in a more or less coordinated way. Thus, these grasshoppers have solitary and gregarious (swarm) phases. Locust swarms can cause massive damage to crops. Important locust species include Schistocerca gregaria and Locusta migratoria in Africa and the Middle East, and Schistocerca piceifrons in tropical Mexico and Central America (Mesoamerica).
Other grasshoppers important as pests (which, unlike true locusts, do not change color when they form swarms) include Melanoplus species (like M. bivittatus, M. femurrubrum and M. differentialis) and Camnula pellucida in North America; the Romalea guttata (lubber grasshopper), Brachystola magna, and Sphenarium purpurascens in northern and central Mexico; species of Rhammatocerus in South America; and the Oedaleus senegalensis (Senegalese grasshopper) and the Zonocerus variegatus (variegated grasshopper) in Africa.
During drought years on the Great Plains during the first half of the 1890s, great clouds of grasshoppers became an uncontrollable pest. They destroyed gardens, crops, grass, and harness. The grasshoppers "cleaned the pastures and fields over which they passed until they were as bare as a floor. They ate harness, coats, or anything that was left outside," reported J. L. Francis of Briscoe County, Texas. N. M. Akeson of Hale County, Texas recalled that the grasshoppers once ate his mail, which he lost on the trail, only to find it in ruins when he came to retrieve it. According to Mrs. Fred Scott of Swisher County, Texas, the grasshoppers "swarmed toward the southwest and ... in such great numbers that they obscured the sun."
- Aesop (620–560 BC), a slave and story-teller who lived in Ancient Greece, told a tale called The Ant and the Grasshopper. In this tale, the ant worked hard preparing his shelter and stores of food all summer, while the grasshopper played. When winter came, the ant was prepared, but the grasshopper has no shelter or food. He begs to enter the ant's house, but the ant refuses and the grasshopper starves.
- Canadian philosopher Bernard Suits contrasts Aesop's grasshopper (the "hero of a cautionary tale") with his own account of the same story. In Suits' version, the grasshopper is "the exemplification of the life most worth living." The Suits grasshopper is focused on game-playing, and Suits' book on the grasshopper is now well known for the definition of "game" it provides: "the voluntary overcoming of unnecessary obstacles." 
- As a result of the popularity of Aesop's fable in Western culture, various other human weaknesses besides improvidence began to be identified with the grasshopper's behaviour. So an unfaithful woman (hopping from man to man) became known as 'a grasshopper'. Portrayal of such women occurs for example in Poprygunya, a short story written in 1892 by Anton Chekhov, and in Jerry Paris' 1969 film "The Grasshopper".
- In the 1998 film A Bug's Life, the heroes are the members of an ant colony, and the lead villain and his henchmen are grasshoppers. In an apparent homage to the Aesop fable, The Ant and the Grasshopper, the lead villain is eaten by a bird.
- Insect Design – Insect Mouth Parts. National Park Service
- Zeuner, F. E. (1939). Fossil Orthoptera Ensifera. London: British Museum Natural History.
- Kevan 1982; Günther, 1980, 1992; Otte 1994–1995
- O'Neill, Kevin M.; Woods, Stephen A.; Streett, Douglas A. (1997). "Grasshopper (Orthoptera: Acrididae) Foraging on Grasshopper Feces: Observational and Rubidium-Labeling Studies". Environmental Entomology 26 (6): 1224–1231.
- Davidowitz, Goggy. Grasshoppers. Arizona-Sonora Desert Museum
- Burrows, M. (1996) The neurobiology of an insect brain. Oxford University Press, Oxford. ISBN 0198523440
- Mechanical power is force x velocity
- Burrows, M. (1995). "Motor patterns during kicking movements in the locust". Journal of Comparative Physiology A 176 (3): 289–305. doi:10.1007/BF00219055. PMID 7707268.
- Heitler, W.J. (1977). "The locust jump III. Structural specializations of the metathoracic tibiae". Journal of Experimental Biology 67: 29–36.
- Bennet-Clark, H. C. (1975). "The energetics of the jump of the locust Schistocerca gregaria". The Journal of experimental biology 63 (1): 53–83. PMID 1159370.
- F. Thomas, A. Schmidt-Rhaesa, G. Martin, C. Manu, P. Durand & F. Renaud (May 2002). "Do hairworms (Nematomorpha) manipulate the water seeking behaviour of their terrestrial hosts?". Journal of Evolutionary Biology (Blackwell Science Ltd.) 15 (3): 356–361. doi:10.1046/j.1420-9101.2002.00410.x.
- Andreas Schmidt-Rhaesa, David G. Biron, Cécile Joly & Frédéric Thomas (2005). "Host–parasite relations and seasonal occurrence of Paragordius tricuspidatus and Spinochordodes tellinii (Nematomorpha) in Southern France". Zoologischer Anzeiger 244 (1): 51–57. doi:10.1016/j.jcz.2005.04.002.
- Capinera, John (2014). "Grasshopper nematode: Mermis nigrescens". Featured Creatures. IFAS. Retrieved 2015-03-28.
- Capinera, John L. (2008). Encyclopedia of Entomology. Springer Science & Business Media. pp. 1229–1230. ISBN 978-1-4020-6242-1.
- Valovage, W. D.; Nelson, D. R. (1990). "Host Range and Recorded Distribution of Entomophaga grylli (Zygomycetes: Entomophthorales), a Fungal Pathogen of Grasshoppers (Orthoptera: Acrididae), in North Dakota". Journal of the Kansas Entomological Society 63 (3): 454–458. JSTOR 25085205.
- Cott, 1940. Pages 25-26
- Cott, 1940. Page 378
- Cott, 1940. Page 291
- Bizarre Foods with Andrew Zimmern aired on the Travel Channel 27 April 2008.
- King, Bes Sie (December 23, 2009). "Snack on grasshoppers". Ny Food Chain (New York: Columbia University Graduate School of Journalism). Retrieved February 24, 2015.
- Sheffy, Lester Fields (1950). The Life and Times of Timothy Dwight Hobart, 1855–1935: Colonization of West Texas. Canyon, Texas: Panhandle-Plains Historical Society. pp. 131–132.
- Suits, Bernard (2005) The Grasshopper: Games, Life and Utopia. Broadview Press. ISBN 1770480110
- Cott, Hugh. Adaptive Coloration in Animals, Oxford University Press, 1940.
- O'Toole, Christopher. (2002) Firefly Encyclopedia of Insects and Spiders ISBN 1-55297-612-2
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- Tree of Life Web Project
- The Grasshopper suicide
- American grasshopper on the UF / IFAS Featured Creatures Web site
- A grasshopper plague is at hand in U.S. | Newsdesk.org (March 30, 2010)
- How Grasshoppers Jump