Migratory locust
Overview
 
The migratory locust is the most widespread locust species, and the only species in the genus Locusta. It occurs throughout Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 and New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

. It used to be common in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 but has now become rare there. Because of the vast geographic area it occupies, which comprises many different ecological zones, numerous subspecies have been described. However, not all experts agree on the validity of some of these subspecies.

Many other species of Orthoptera with gregarious and migratory behavior are indicated with the name of 'locusts'.
The migratory locust is polyphenic
Polyphenism
A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions.-Definition:A polyphenism is a biological mechanism that causes a trait to be polyphenic...

.
Encyclopedia
The migratory locust is the most widespread locust species, and the only species in the genus Locusta. It occurs throughout Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 and New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

. It used to be common in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 but has now become rare there. Because of the vast geographic area it occupies, which comprises many different ecological zones, numerous subspecies have been described. However, not all experts agree on the validity of some of these subspecies.

Many other species of Orthoptera with gregarious and migratory behavior are indicated with the name of 'locusts'.

Polyphenism

The migratory locust is polyphenic
Polyphenism
A polyphenic trait is a trait for which multiple, discrete phenotypes can arise from a single genotype as a result of differing environmental conditions.-Definition:A polyphenism is a biological mechanism that causes a trait to be polyphenic...

. It transitions between two main phenotypes in response to population density; the solitary phase and the gregarious phase. As the density of the population increases the locust transforms progressively from the solitary phase towards the gregarious phase with intermediate phases:

Solitaire = solitary phase → transiens congregans (intermediate form) → gregarious phase → transiens dissocians (intermediate form) → solitaire = solitary phase.

Pigmentation and size of the migratory locust vary according to its phase (gregarious or solitary form) and its age. Gregarious larvae have a yellow to orange covering with black spots. Solitary larvae are green or brown. The gregarious adult is brownish with yellow, the latter colour becoming more intense and extensive on maturation. The solitary adult is brown with varying extent of green colour depending on the colour of the vegetation. Gregarious adults vary in size between 40 and 60 mm according to the sex. They are smaller than the solitary adults.

Economic Impact

Locusts are highly mobile, and usually fly with the wind at a speed of about 15-20 km/h. Swarms can travel 5-130 km or more in a day. Locust swarms can vary from less than one square kilometre to several hundred square kilometres with 40 to 80 million individuals per square kilometre. An adult locust can consume its own weight (about 2 grams) in fresh food per day. For every million locusts, one ton of food is eaten.

In Africa, the last serious widespread plague of Locusta m. migratorioides occurred from 1928 to 1942. Since then, environmental transformations have made the development of swarms from the migratory locust unlikely. However, the desert locust
Desert locust
Plagues of the desert locust have threatened agricultural production in Africa, the Middle East, and Asia for centuries. The livelihood of at least one-tenth of the world’s human population can be affected by this voracious insect...

 which is very similar to the African migratory locust remains a major threat. Nevertheless potential outbreaks are constantly monitored as plagues can be devastating.

Locust survey and control are primarily the responsibility of the Ministry of Agriculture in locust-affected countries and are operations undertaken by national locust units. The Food and Agriculture Organization
Food and Agriculture Organization
The Food and Agriculture Organization of the United Nations is a specialised agency of the United Nations that leads international efforts to defeat hunger. Serving both developed and developing countries, FAO acts as a neutral forum where all nations meet as equals to negotiate agreements and...

 (FAO) of the United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

 provides information on the general locust situation to all interested countries and gives warnings and forecasts to those countries in danger of invasion.

List of 'locusts'

  • American desert locust Schistocerca americana
  • Australian plague locust
    Australian plague locust
    The Australian plague locust is a native Australian insect in the family Acrididae and a significant agricultural pest....

     Chortoicetes terminifera
  • Bombay locust Nomadacris succincta
  • Brown locust
    Brown locust
    The brown locust, Locustana pardalina, is a medium-sized small locust species found in Southern Africa and shows classic gregarious behaviour with phase polymorphism) on crowding.-Biology:...

     Locustana pardalina
  • Desert locust
    Desert locust
    Plagues of the desert locust have threatened agricultural production in Africa, the Middle East, and Asia for centuries. The livelihood of at least one-tenth of the world’s human population can be affected by this voracious insect...

     Schistocerca gregaria
  • Italian locust Calliptamus italicus
  • Migratory locust
    Migratory locust
    The migratory locust is the most widespread locust species, and the only species in the genus Locusta. It occurs throughout Africa, Asia, Australia and New Zealand. It used to be common in Europe but has now become rare there...

     Locusta migratoria
  • Moroccan locust Dociostaurus maroccanus
  • Red locust
    Red locust
    The Red Locust is a large grasshopper species found south of the Sahara in Africa. Its name refers to the colour of its hindwings. It is sometimes called the Criquet nomade in French, due to its nomadic movements in the dry season.-Adults:...

     Nomadacris septemfasciata
  • Rocky Mountain locust
    Rocky Mountain locust
    The Rocky Mountain locust was the locust species that ranged through almost the entire western half of the United States until the end of the 19th century...

     Melanoplus spretus – extinct
  • Spur-throated locust
    Spur-throated locust
    The Spur-throated locust is a native Australian insect in the family Acrididae and a significant agricultural pest.Adult females of A. guttulosa are typically long, and adult males are typically long.-See also:...

    , Australis procera - Australia
  • Three locusts Anacridium spp.
    • Anacridium aegyptium
      Anacridium aegyptium
      Anacridium aegyptium, the 'Egyptian Locust', is a species belonging to the family Acrididae subfamily Cyrtacanthacridinae.It is present in most of Europe, in the 'Afro-tropical ecozone', in eastern Palearctic ecozone, in the Near East and in North Africa.It is one of the largest European...

    • Anacridium melanorhodon
    • Anacridium wernerellum

Borderline species

  • Senegalese grasshopper
    Senegalese grasshopper
    Oedaleus senegalensis is a medium-sized grasshopper species found in the Sahel region of Africa, the Canary Islands, Cape Verde Islands and West Asia. Although not called a locust in English, this species shows gregarious behaviour and some morphological change on crowding...

     Oedaleus senegalensis - often displays locust-like behaviour in the Sahel region
  • Sudan plague locust Aiolopus simulatrix - occasionally behaves like a locust in eastern Sudan

Subspecies of Locusta migratoria

  • Locusta migratoria var. burmana Ramme, 1951
  • Locusta migratoria var. capito Saussure, 1884 (Madagascar)
  • Locusta migratoria var. cinerascens Fabricius, 1781 (Italy, Spain)
  • Locusta migratoria var. manilensis (Meyen, 1835) 1 (eastern Asia)
  • Locusta migratoria var. migratoria (Linnaeus, 1758) (West and Central Asia, eastern Europe)
  • Locusta migratoria var. migratorioides (Fairmaire & L.J. Reiche, 1849) (mainland Africa and Atlantic islands)
  • Locusta migratoria var. tibetensis Chen, Yonglin, 1963
  • Locusta migratoria var. danica (Linnaeus, 1767) - Locusta migratoria var. migratoria (Linnaeus, 1758)
  • Locusta migratoria var. gallica Remaudičre, 1947 - Locusta migratoria var. migratoria (Linnaeus, 1758)
  • Locusta migratoria var. solitaria Carthy, 1955 - Locusta migratoria var. migratoria (Linnaeus, 1758)

External links

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