Red locust
Encyclopedia
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.
Males are 60-70 mm (2.4-2.8 inches) long; females are 60-85 mm (2.4-3.3 inches) long.
s. Grain
s are their primary food source, so grassy lowlands are prime habitat. They also like spending time in trees and thus prefer some tree cover.
Red locusts are sedentary when ample shelter, perches and food is available. In dry years, when the amount of suitable habitat is
reduced population densities increase. If the population density increases past a threshold, the locusts will transform into their gregarious phase, changing their behaviour and anatomy. When gregarious, red locusts keep together in large swarms and fly with the wind in daylight hours, looking for more food. The higher temperatures during daylight enable gregarious locusts to travel longer distances by flying longer and higher, aided by thermal lift
. A swarm will rarely move more than 20-30km in a day.
In contrast, solitary locusts prefer to fly in the dark and do so alone
.
Compared to their solitary phase, gregarious red locusts also have:
Swarming females often lay eggs at night. Their youngsters immediately behave gregariously and are capable of "hopping" hundreds of metres every day.
, Tanzania
, Malawi
and also Madagascar
and Réunion
. In the Sahel
, the species is observed on a more incidental basis in Cape Verde
, the central Niger River
delta in Mali
and around Lake Chad
. The last widespread plague occurred from 1930-1944, when almost all of southern Africa was invaded.
After unsuccessful efforts to control the locusts through environmental modifications, chemical agents are currently being used. A biological product based on a pathogenic fungus
(Metarhizium anisopliae
var. acridum) is now available (see desert locust
). It has been successfully tested on both nymphs and adults of the red locust.
Grasshopper
The grasshopper is an insect of the suborder Caelifera in the order Orthoptera. To distinguish it from bush crickets or katydids, it is sometimes referred to as the short-horned grasshopper...
species found south of the Sahara
Sahara
The Sahara is the world's second largest desert, after Antarctica. At over , it covers most of Northern Africa, making it almost as large as Europe or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean...
in 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...
. Its name refers to the colour of its hindwings. It is sometimes called the Criquet nomade in French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
, due to its nomadic movements in the dry season.
Adults
The overall colour of adult insects is a mixture of light beige and brown. They have seven brown transversal bands on the elytra, justifying the species name septemfasciata. The pronotum has two brown lateral bands.Males are 60-70 mm (2.4-2.8 inches) long; females are 60-85 mm (2.4-3.3 inches) long.
Hoppers
Unlike adults, the colour of immature insects varies depending on their phase. When solitary they can be green or brown; when in large numbers (gregarious), they are bright yellow and red-brown with black markings.Ecology
Red locusts actively seek out moist environments such as seasonal floodplainFloodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
s. Grain
GRAIN
GRAIN is a small international non-profit organisation that works to support small farmers and social movements in their struggles for community-controlled and biodiversity-based food systems. Our support takes the form of independent research and analysis, networking at local, regional and...
s are their primary food source, so grassy lowlands are prime habitat. They also like spending time in trees and thus prefer some tree cover.
Red locusts are sedentary when ample shelter, perches and food is available. In dry years, when the amount of suitable habitat is
reduced population densities increase. If the population density increases past a threshold, the locusts will transform into their gregarious phase, changing their behaviour and anatomy. When gregarious, red locusts keep together in large swarms and fly with the wind in daylight hours, looking for more food. The higher temperatures during daylight enable gregarious locusts to travel longer distances by flying longer and higher, aided by thermal lift
Thermal
A thermal column is a column of rising air in the lower altitudes of the Earth's atmosphere. Thermals are created by the uneven heating of the Earth's surface from solar radiation, and are an example of convection. The sun warms the ground, which in turn warms the air directly above it...
. A swarm will rarely move more than 20-30km in a day.
In contrast, solitary locusts prefer to fly in the dark and do so alone
.
Compared to their solitary phase, gregarious red locusts also have:
- reduced lifespan
- more markings
- 6 instar stagesInstarAn instar is a developmental stage of arthropods, such as insects, between each molt , until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in altered body proportions, colors, patterns, or...
rather than 7 - longer sexual maturation
- larger and heavier young, although they lay fewer eggs
Swarming females often lay eggs at night. Their youngsters immediately behave gregariously and are capable of "hopping" hundreds of metres every day.
Outbreaks
Outbreak areas have been identified in ZambiaZambia
Zambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....
, Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
, Malawi
Malawi
The Republic of Malawi is a landlocked country in southeast Africa that was formerly known as Nyasaland. It is bordered by Zambia to the northwest, Tanzania to the northeast, and Mozambique on the east, south and west. The country is separated from Tanzania and Mozambique by Lake Malawi. Its size...
and also Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
and Réunion
Réunion
Réunion is a French island with a population of about 800,000 located in the Indian Ocean, east of Madagascar, about south west of Mauritius, the nearest island.Administratively, Réunion is one of the overseas departments of France...
. In the Sahel
Sahel
The Sahel is the ecoclimatic and biogeographic zone of transition between the Sahara desert in the North and the Sudanian Savannas in the south.It stretches across the North African continent between the Atlantic Ocean and the Red Sea....
, the species is observed on a more incidental basis in Cape Verde
Cape Verde
The Republic of Cape Verde is an island country, spanning an archipelago of 10 islands located in the central Atlantic Ocean, 570 kilometres off the coast of Western Africa...
, the central Niger River
Niger River
The Niger River is the principal river of western Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in southeastern Guinea...
delta in Mali
Mali
Mali , officially the Republic of Mali , is a landlocked country in Western Africa. Mali borders Algeria on the north, Niger on the east, Burkina Faso and the Côte d'Ivoire on the south, Guinea on the south-west, and Senegal and Mauritania on the west. Its size is just over 1,240,000 km² with...
and around Lake Chad
Lake Chad
Lake Chad is a historically large, shallow, endorheic lake in Africa, whose size has varied over the centuries. According to the Global Resource Information Database of the United Nations Environment Programme, it shrank as much as 95% from about 1963 to 1998; yet it also states that "the 2007 ...
. The last widespread plague occurred from 1930-1944, when almost all of southern Africa was invaded.
After unsuccessful efforts to control the locusts through environmental modifications, chemical agents are currently being used. A biological product based on a pathogenic fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
(Metarhizium anisopliae
Metarhizium anisopliae
Metarhizium anisopliae, formerly known as Entomophthora anisopliae , is a fungus that grows naturally in soils throughout the world and causes disease in various insects by acting as a parasite. Ilya I. Mechnikov named it after the insect species it was originally isolated from: the beetle...
var. acridum) is now available (see 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...
). It has been successfully tested on both nymphs and adults of the red locust.