# Locust — Facts, Threats & Conservation

*Grasshoppers (Acrididae) in the gregarious phase — e.g. Schistocerca gregaria (Forskål, 1775), the desert locust*

> A locust is a grasshopper (family Acrididae) in its gregarious phase — triggered by crowding, it changes colour, shape and behaviour and forms swarms; the desert locust (Schistocerca gregaria) can devastate crops across Africa, the Middle East and southern Asia.

**IUCN status:** Not Evaluated — pest swarms are a phase, not a separate species; desert locust has no global Red List entry  ·  **WARN range:** Africa, the Middle East and southern Asia for desert locust, Other locust species on every inhabited continent

## Quick facts
| Fact | Value |
| --- | --- |
| Adult length | Roughly 6–9 cm in desert locust |
| Diet | Green vegetation and crops |
| Habitat | Arid breeding belts; swarms travel widely |
| Phase trigger | Crowding and tactile stimulation |
| Plague species | Schistocerca gregaria — desert locust |
| Human risk | Crop damage, not venom or bite |

## Scientific classification
- **Kingdom:** Animalia
- **Phylum:** Arthropoda
- **Class:** Insecta
- **Order:** Orthoptera
- **Family:** Acrididae
- **Species:** Schistocerca gregaria — desert locust (best-known plague species)
- **Phase:** Solitary versus gregarious — same species, different phenotype

## Conservation status
- **Status:** Not Evaluated
- **Population:** Swarm populations can reach billions during outbreaks
- **Trend:** Cyclic — plague years versus recession years
- **Assessed:** Desert locust not globally Red-Listed
- **CITES:** Not listed
- Locust management is about agricultural impact, not species rarity. Outbreaks reflect phase dynamics and weather, not population collapse.

## Key facts: Locust
- Locusts are grasshoppers in a gregarious phase — not a separate taxonomic group.
- Crowding — especially tactile stimulation from other locusts — triggers the phase change.
- Gregarious locusts differ in colour, body proportions, activity and tendency to swarm.
- The desert locust (Schistocerca gregaria) is the species behind most transcontinental plague events.
- Swarms can travel with wind and cross borders; control requires international coordination.
- Solitary-phase locusts look and behave like ordinary grasshoppers and are easily overlooked.

## One species, two bodies — phenotypic plasticity
Solitary-phase Schistocerca gregaria is green or brown, avoids other locusts, and moves relatively little. Raise density in a laboratory or field cage until individuals touch repeatedly, and within hours to days the offspring and sometimes the adults shift toward gregarious traits: stronger yellow and black colouration, longer wings relative to body, higher activity and attraction to others of the same species.

The switch involves serotonin signalling in the central nervous system — a neurochemical cascade linking touch stimulus to behavioural and developmental change. Reverse the crowding and successive moults can move the population back toward solitary form. One genome produces two ecologically different animals depending on population density.

## Swarms, migration and crop damage
Gregarious desert locusts form bands on the ground that march in the same direction, then take wing as adults in swarms that follow wind and vegetation flushes. A single swarm can contain billions of insects and consume its own weight in green vegetation daily — a figure often quoted in plague reporting and one that scales terrifyingly with swarm mass even when the per-insect rate is ordinary for a large herbivorous insect.

Breeding areas span roughly 16 million square kilometres across more than 60 countries from West Africa to India. Drought followed by rainfall can trigger simultaneous hatching and crowding, initiating a plague cycle that may persist for years if control and weather align against it. Crop loss hits subsistence farmers first; international monitoring through the Food and Agriculture Organization coordinates survey and treatment.

## Why ordinary grasshopper control is not locust control
Spraying a garden grasshopper does not address a transcontinental plague species. Locust management relies on early detection of gregarious bands in remote breeding areas, targeted application of approved pesticides or biological agents such as Metarhizium fungus, and cross-border reporting obligations under international agreements.

Confusing a solitary locust-capable grasshopper with a non-swarming species is harmless; confusing a forming band with ordinary hopper density is not. The phase change is the diagnostic: gregarious nymphs march together in coordinated bands rather than dispersing. That behaviour is visible from the ground and in satellite-assisted survey programmes.

## Climate, conflict and the next outbreak
Locust plagues correlate with weather patterns that produce green vegetation in normally dry breeding belts — often after drought breaks. War and inaccessible territory complicate survey: undetected bands in Yemen or the Sahel can seed swarms that reach other countries before control begins.

Schistocerca gregaria is not Red-Listed as a species because it is abundant by definition during outbreaks. The human problem is agricultural and economic, not extinction risk. Other locust species — Australian plague locust, migratory locust in Asia — follow similar phase logic on regional scales.

## What WARN does
WARN publishes free insect education that explains mechanisms, not just headlines. Locust plagues are a phase-change story — understanding crowding and phenotypic plasticity is what separates informed reporting from plague panic.

If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.

## Frequently asked questions: Locust
### What do locusts eat?
Locusts eat green vegetation — leaves, stems, shoots and crops. Gregarious desert locust swarms consume enormous quantities of plant biomass daily; a swarm's total intake scales with its mass and can devastate fields and pasture.

### Where do locusts live?
Locust-capable grasshopper species occur on every inhabited continent. The desert locust breeds in arid and semi-arid belts from West Africa through the Middle East to India, with swarms travelling far beyond breeding areas on wind.

### Are locusts dangerous to humans?
Locusts do not bite or sting people in any serious way. The danger is agricultural — crop and pasture loss — and the economic harm that follows, particularly where subsistence farming has no buffer.

### How long do locusts live?
Individual desert locusts live a few months from egg to adult death, with timing driven by temperature and food. Plague cycles persist across years through successive generations, not through long-lived individuals.

### How big are locusts?
Desert locust adults are roughly 6–9 cm long with wings folded. Gregarious-phase individuals may differ in proportions from solitary-phase ones — longer wings and different colouration are part of the phase change.

### What is the difference between a locust and a grasshopper?
A locust is a grasshopper species capable of switching into a gregarious phase when crowded. Not all grasshoppers are locusts — only those with the genetic capacity for phase change. In solitary phase they resemble ordinary grasshoppers.

## Sources
- [FAO — Desert Locust Information Service](https://www.fao.org/ag/locusts/en/info/info/index.html)
- [IUCN Red List](https://www.iucnredlist.org/)

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Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/locust