The
migratory locust (
Locusta migratoria) is the most widespread locust species. It occurs throughout
AfricaAfrica 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. With a billion people in 61 territories, it accounts for about 14.8% of the...
,
AsiaAsia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...
,
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
and
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous smaller islands, most notably Stewart Island/Rakiura and the Chatham Islands. The indigenous Māori named New Zealand Aotearoa, commonly translated as The Land of the Long White Cloud...
. It used to be common in
EuropeEurope 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 water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
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.
The
migratory locust (
Locusta migratoria) is the most widespread locust species. It occurs throughout
AfricaAfrica 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. With a billion people in 61 territories, it accounts for about 14.8% of the...
,
AsiaAsia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...
,
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
and
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous smaller islands, most notably Stewart Island/Rakiura and the Chatham Islands. The indigenous Māori named New Zealand Aotearoa, commonly translated as The Land of the Long White Cloud...
. It used to be common in
EuropeEurope 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 water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
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. The main ones are:
- Locusta migratoria migratoria (West and Central Asia, eastern Europe)
- Locusta migratoria migratorioides (mainland Africa and Atlantic islands)
- Locusta migratoria capito (Madagascar)
- Locusta migratoria manilensis (eastern Asia)
A polyphenic insect
They transform enormously behaviourally and physically under the effect of population density and are thus called polyphenic insects, or
locustLocust is the swarming phase of short-horned grasshoppers of the family Acrididae. The origin and apparent extinction of certain species of locust—some of which reached 6 inches in length—are unclear....
.
There are two main phases:
- The solitary phase
- 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.
Other common locust are
Schistocerca gregaria and
Nomadacris septemfasciata
Pigmentation and size of the migratory locust
Pigmentation and size of the migratory locust vary according to its state (gregarious or solitary or intermediate form) and its age (larva, mature or immature adult).
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.
Often confused with the desert locust, there are some major differences between the migratory and desert locust.
A Devastating Insect
Locusts are highly mobile, and usually fly with the wind at a speed of about 15-20 km/h. Swarms can travel about 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 locust 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.
Still a major threat?
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 locustPlagues 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 OrganizationThe 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 debate policy...
(FAO) of the
United NationsThe United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and the achieving 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.