What are locusts?

Locusts have been feared and revered throughout history. Related to grasshoppers, these insects form enormous swarms that spread across regions, devouring crops and leaving serious agricultural damage in their wake. Plagues of locusts have devastated societies since the Pharaohs led ancient Egypt, and they still wreak havoc today.

Behavior and life cycle

Locusts look like ordinary grasshoppers—most notably, they both have big hind legs that help them hop or jump. They sometimes share the solitary lifestyle of a grasshopper, too. However, locust behavior can be something else entirely.

During dry spells, solitary locusts are forced together in the patchy areas of land with remaining vegetation. This sudden crowding releases serotonin in their central nervous systems that makes locusts more sociable and promotes rapid movements and more varied appetite.

When rains return—producing moist soil and abundant green plants—those environmental conditions create a perfect storm: Locusts begin to produce rapidly and become even more crowded together. In these circumstances, they shift completely from their solitary lifestyle to a group lifestyle in what’s called the gregarious phase. Locusts can even change color and body shape when they move into this phase. Their endurance increases and even their brains get larger.

Locusts can become gregarious at any point in their lifecycle. On hatching, a locust emerges wingless as a nonflying nymph, which can be either solitary or gregarious. A nymph can also change between behavior phases before becoming a flying adult after 24 to 95 days.

the life of a locust

Locusts move through several phases before maturing into flying adults. At any point in that process they can turn gregarious—if conditions are right. Transformations in their behavior and physical traits can eventually be reversed, or they can persist and be passed on to offspring.

Desert locust

Schistocerca gregaria

relative size

Egg

10-65 days

Nonflying nymph

24-95 days

Solitary

Gregarious

Flying adult

2.5-5 months

Gregarious

Solitary

Taylor maggiacomo, NGM Staff. SOURCES: Stephen Rogers, University of Cambridge; STEPHEN J. SIMPSON, UNIVERSITY OF SYDNEY; Keith Cressman, FAO Desert Locust Information Service

the life of a locust

Locusts move through several phases before maturing into flying adults. At any point in that process they can turn gregarious—if conditions are right. Transformations in their behavior and physical traits can eventually be reversed, or they can persist and be passed on to offspring.

Desert locust

Schistocerca gregaria

relative size

Egg

10-65 days

Solitary

Gregarious

Nonflying nymph

(hopper)

24-95 days

Flying adult

2.5-5 months

Taylor maggiacomo, NGM Staff. SOURCES: Stephen Rogers, University of Cambridge; STEPHEN J. SIMPSON, UNIVERSITY OF SYDNEY; Keith Cressman, FAO Desert Locust Information Service

Swarming

Locust swarms are typically in motion and can cover vast distances—some species may travel 81 miles or more a day. They can stay in the air for long periods, regularly taking nonstop trips across the Red Sea. In 1954, a swarm flew from northwest Africa to Great Britain, while in 1988, another made the lengthy trek from West Africa to the Caribbean, a trip of more than 3,100 miles in just 10 days.

Locust swarms devastate crops and cause major agricultural damage, which can lead to famine and starvation. Locusts occur in many parts of the world, but today locusts are most destructive in subsistence farming regions of Africa.

where swarms occur

The species with the most economic impact, the desert locust, threatens one-fifth of Earth’s land area and one-tenth of the global population. Over 60 countries are susceptible to swarms. Locusts in the solitary phase occupy and breed in smaller regions. The last major plague, from 1986 to 1989, hit North Africa and the Middle East. Many swarms died while crossing the Atlantic; some reached the Caribbean.

Desert locust

Schistocerca gregaria

Solitary range

Swarming range

Swarm reports 1985-2019

EUROPE

ASIA

INDIAN

OCEAN

AFRICA

ATLANTIC

OCEAN

Preventing a plague

Weather patterns and historical locust records help experts predict where swarms might form. Once identified, an area is sprayed with chemicals to kill locusts before they can gather.

Riley D. Champine, NGM Staff

SOURCe: Keith Cressman, FAO Desert Locust Information Service

where swarms occur

The species with the most economic impact, the desert locust, threatens one-fifth of Earth’s land area and one-tenth of the global population. Over 60 countries are susceptible to swarms. Locusts in the solitary phase occupy and breed in smaller regions. The last major plague, from 1986 to 1989, hit North Africa and the Middle East.

EUROPE

ASIA

INDIAN

OCEAN

AFRICA

Desert locust

Schistocerca gregaria

ATLANTIC

OCEAN

Solitary range

Swarming range

Swarm reports

1985-2019

Preventing a plague

Weather patterns and historical locust records help experts predict where swarms might form. Once identified, an area is sprayed with chemicals to kill locusts before they can gather.

Riley D. Champine, NGM Staff. SOURCE: Keith Cressman, FAO Desert Locust Information Service

Desert locusts

The desert locust (Schistocerca gregaria) is a notorious species. Found in Africa, the Middle East, and Asia, this species inhabits an area of about six million square miles, or 30 countries, during a quiet period. During a plague, when large swarms descend upon a region, however, these locusts can spread out across some 60 countries and cover a fifth of Earth's land surface. Desert locust plagues threaten the economic livelihood of a tenth of humans.

A desert locust swarm can be 460 square miles in size and pack between 40 and 80 million locusts into less than half a square mile. Each locust can eat its weight in plants each day, so a swarm of such size would eat 423 million pounds of plants every day. To put it into context, a swarm the size of Paris can eat the same amount of food in one day as half the population of France.

Prevention

There are many reasons why it’s difficult to control or prevent a plague of locusts, including the remoteness and breadth of the areas across which they’re spread and limited resources in some of the affected countries. But experts can look at past weather patterns and historical records to identify the areas where swarms might occur and spray those areas with chemicals.


Some experts worry that locust plagues will worsen in a warming world. Rising sea temperatures are causing prolonged bouts of wet weather, including a surge of rare cyclones in eastern Africa and the Arabian Peninsula where desert locusts thrive.