Locusts have been agricultural pests for almost as long as humans have grown plants for food. They cause millions of dollars in crop damage every year. They can even create food shortages and destroy entire livelihoods in certain regions of the world.
There are many different species of locusts around the world, and they all can form massive swarms of thousands to millions of insects.
What Are Locusts?
Locusts are a type of grasshopper in the Orthoptera order, which also includes crickets, katydids, and other straight-winged insects. Most locusts are part of the Acrididae family.
Scientists are still trying to find out the exact number of locust species in the world today. This is tricky because there are so many different varieties of these insects. For example, there are over 700 species of locusts and other grasshoppers living in Australia alone.
All species of locusts are short-horned grasshoppers that sometimes form large, hungry swarms. The swarms migrate together and destroy most of the plant life in their path.
Most locust species only form swarms when a lot of them are present in one spot. The high population density causes them to go through both physical and behavioral changes that are more suitable for life in a swarm. This biological phenomenon is called polyphenism.
What do locusts look like?
Members of each species of locust have their own average sizes and coloration patterns. Individuals within a species develop differently when they’re in a swarm than they do when surviving on their own. Their swarm forms are also known as their gregarious forms.
For the most part, they resemble chunky grasshoppers with very strong wings. The wings typically don’t form until they reach the adult stage of their life cycle.
Examples of colors that you could see on a locust’s adult body include:
- Brown
- Green
- Straw
- Gray
Some adults also have distinct patterns on their bodies, such as white stripes. Within a species, an individual's exact color can depend on whether it’s living by itself or in a swarm.
Body sizes can range from 1.25 inches to over 2 inches long. In many species, males are smaller than females.
What’s the locust’s life cycle?
Throughout their lifetime, locusts go through incomplete metamorphosis. This means that they never form maggot-like pupae. Instead, young locusts — called nymphs — are mostly just smaller versions of their adult forms.
All locust species hatch from eggs and then grow through a series of nymph stages, called instars. The exact number of instars depends on the locust species. Many have five separate instar stages. To grow larger, they molt between each stage.
Many species only survive for a single season, but others can last a year or two.
What do locusts eat?
Locusts are herbivores. This means they survive off of plants. While the specific plants vary by species, most prefer to feed on human crops, including:
Most species prefer plant leaves, but they can also eat flowers and other plant parts.
Locusts vs. grasshoppers
Locusts are a type of grasshopper but behave differently when they swarm. Other grasshoppers behave as individuals. Locusts may behave as individuals when their population density is low.
When it is high, locusts act in groups, and each locust may go through physiological and behavioral changes as a result. The physical changes may include changes in body shape, color, fertility, physiology, and survival. Behaviorally, they may migrate long distances.
Types of Locusts
These are the most common locusts.
Locusta migratoria
Members of this species are commonly called migratory locusts. These are large, blocky locusts. Solitary adults take on green and brown tones. Their bodies are more straw-colored in their swarm form. This species mainly consumes grasses — such as sorghum, wheat, and corn. They thrive in a wide variety of agricultural areas around the globe.
Austracris guttulosa
The spur-throated locust is named after a distinct protrusion that you can find between its front legs. Adults are pale brown with white stripes. They feed on a wide variety of crops, but most people don’t consider them as problematic a pest as other species.
Schistocerca gregaria
This species is also known as the desert locust. It’s one of the most devastating agricultural pests alive today. It’s threatened the livelihoods of millions of people throughout Africa, Asia, and the Middle East. Desert locusts have yellowish bodies with distinct black stripes.
Melanoplus spretus
This is the Rocky Mountain locust. A living example hasn’t been seen since 1902, so experts believe that they’re extinct. The species formed a final swarm in 1874 that was composed of over 12.4 trillion insects. Any crops that were growing in this swarm’s path were destroyed.
Locust Swarms
A swarm is a large cluster of adult locusts that may contain tens of millions of insects. A swarm can spread over several square miles of farm fields.
A swarm forms when a locust population increases to the point that individuals crowd each other. When that happens, a locust population may grow as much as 20 times its size in three months and reach a density of more than 200 million insects per square mile.
Such a swarm may consume as much grain in a day as would be eaten by 87,500 people.
Historical locust plagues
Perhaps the most well-known locust plague was mentioned in the Bible's Book of Exodus, in which Moses tells Pharaoh that locusts "will cover the face of the ground so that it cannot be seen. They will devour what little you have left after the hail, including every tree that is growing in your fields."
More recently, locust swarms have happened around the globe, including North America, Europe, the Middle East, and Africa.
In 1875, the so-called Albert’s swarm of trillions of locusts covered 198,000 square miles of four U.S. states, an area larger than the entire state of California.
In 1915, locusts devastated the fields of the Middle East, including Syria and Palestine.
And between 2019 and 2022, desert locusts attacked food crops across 23 countries, from Pakistan to Tanzania, affecting parts of East Africa, the Arabian Peninsula, and portions of India, threatening as much as 20% of the world’s land mass.
Where Do Locusts Live?
You can find different species of locusts living in most parts of the world, except in Antarctica. Many species particularly enjoy agricultural areas because these provide them with plenty of food to choose from.
Swarms only form when certain environmental conditions are met. Researchers are still trying to understand exactly what conditions are required for swarming in every locust species.
Signs You Have Locusts
When locusts swarm, they can appear and disappear very suddenly. In this case, the sign will be the large cloud of insects descending on your home or field. But by this time, it’s too late.
Unique environmental conditions, such as the amount of seasonal rainfall and the ambient temperature, can cause each species to swarm. Learn about the species that are most common in your area. Then figure out the environmental conditions that are likely to cause this species to swarm. Take more precautions in years that match these conditions than in years that don’t.
Are Locusts Dangerous?
For the most part, locusts are only a major pest in the agricultural industry. For some, the economic impact of locusts can be huge. Locust swarms can take out an entire season’s worth of crops in a single feeding session. This can translate to 100% crop loss in the span of a few hours.
A swarm won’t hesitate to destroy your backyard garden if they happen to be passing through.
Do locusts bite?
Locusts can bite, but they aren’t known for biting humans. If you feel pain after interacting with a locust, it’s probably because they stabbed you with their strong legs or the sharp spurs that are found on some species.
How to Treat a Locust Exposure
Locusts shouldn’t cause you a lot of physical harm. You shouldn’t require treatment after interacting with locusts.
But you should always keep an eye out for signs of an allergic reaction if you’re bitten or stung by any type of insect. Get immediate medical attention if you start to experience any serious symptoms, such as difficulty breathing, swelling in your throat or face, and hives.
How to Get Rid of Locusts
Managing locusts is a tricky problem that requires large-scale coordinated efforts. Multiple organizations are responsible for tracking their yearly movements and giving farmers early warnings when swarms start to form in any given area.
The main way to manage them at present is with large amounts of commercial pesticides. But this practice can damage the environment in other serious ways.
Researchers are currently exploring new ways to sustainably manage these pests. A lot of this involves understanding why swarms form in the first place, so we can keep this from happening.
On the home garden front, you can keep plants safe by moving them indoors or covering them up when you know that a swarm is on the way.
Locusts have behaved as devastating pests for thousands of years. Humanity is still trying to figure out how to manage these problematic insects. But they’re also fascinating biological models. Learn about the types of locusts that are present in your area so you know how to protect your plants when a swarm is on its way.
Locust FAQs
Why do locust swarms form?
Swarms result from high locust population density and external stresses on a locust population.
Those can include weather, such as sudden rainfall or flooding that pushes a population of locusts into a limited space.
Some species of locusts also swarm to migrate for food elsewhere.
How are locusts controlled and managed?
Farmers spray insecticides on the ground to control locusts. These can be chemical or biological, such as certain types of fungi that are lethal to locusts.
The downside to chemical insecticides is that they may leave harmful residues, particularly if they are used near livestock or on food crops.
Regulators advise a period of inactivity after spraying of chemical pesticides to allow the residues to clear.
Have locust swarms occurred recently?
The most recent massive outbreak of locust swarms occurred between 2019 and 2022.
Locust swarms are always possible in areas where locust species prevail, depending on environmental conditions.
Can locusts be beneficial?
Research has shown that locusts may be a nutritious and abundant food source with nutritional value equivalent to that of animal meat, without the environmental costs of livestock.
People in 65 countries have traditionally incorporated about 10 species of locusts as part of their regular diet for thousands of years.
Some nations have already developed regulations about which locusts are safe to eat and to protect people from eating those contaminated with insecticide residues or other contaminants.