Locust

Phase change, not species

The “locust” isn’t a separate species from the grasshopper — it’s a behavioral and morphological phase that certain grasshopper species can switch into. The trigger is density:

• At low population density, the grasshopper exists in a solitary phase — typically green or brown, mild-mannered, slow-reproducing.
• At high density (triggered by repeated touch on the back legs), serotonin levels rise. Within hours, the same insect changes:
  • Color — from green/brown to black/yellow
  • Body — wings grow longer
  • Behavior — gregarious instead of solitary
  • Reproduction — more eggs per female
  • Offspring — born in the gregarious phase

The two phases were once considered separate species. The discovery that they’re the same species in different states was made in 1921 by Boris Uvarov.

Devastating swarms

A mature locust swarm can:

• Contain 40 billion individuals in a single coordinated cloud.
• Cover 1,000 square kilometers.
• Eat its own body weight in vegetation per day — collectively consuming the food of millions of people.
• Travel hundreds of kilometers per day on prevailing winds.

The 2019–2022 East African locust crisis was one of the worst in 70 years, threatening food security for millions across Kenya, Ethiopia, Somalia, and Yemen.

A biblical scourge

Locust swarms are mentioned in religious texts going back thousands of years — the Eighth Plague of Egypt in Exodus is among the earliest written descriptions. Locust outbreaks have repeatedly contributed to famines in Africa and the Middle East throughout recorded history.

Modern control

Modern locust control uses:

• Aerial pesticide spraying — coordinated by FAO and national agriculture ministries.
• Biological pesticides — fungal pathogens like Metarhizium acridum that infect only grasshoppers and locusts.
• Early warning systems — satellite monitoring for breeding-favorable rainfall.
• Manual destruction of egg pods and bands of nymphs.

Despite modern tools, swarms still escape control when monitoring lapses (often due to political instability in source regions) and become continental-scale disasters.

Edible

In several cultures, locusts are food. Africa, the Middle East, and Mexico have traditions of frying locusts with salt and chili. They’re high in protein (about 60% by dry weight), and Jewish dietary law specifically permits four species (one of the few insects permitted under kashrut).