The Desert Locust: From Harmless Hopper to Devastating Plague

Imagine a swarm so vast it darkens the sky, consuming everything in its path. This is the reality of a desert locust plague, a phenomenon that can transform fertile lands into barren wastelands. But what triggers this dramatic shift from solitary insect to a member of a crop-devouring horde?

The Solitary Life of a Desert Locust

Most of the time, desert locusts are unassuming creatures, no more threatening than common grasshoppers. They inhabit arid regions stretching from North Africa to South Asia, where they live a solitary existence. These adolescent hoppers spend their days foraging for scarce vegetation, eventually growing wings, reproducing, and completing their short life cycle.

The Transformation: When Rain Triggers a Plague

The transformation begins with an abundance of rain. Increased moisture leads to more vegetation, allowing newly hatched hoppers to feed in close proximity. This crowding is the catalyst for a remarkable change.

• Stimulated Leg Hairs: Frequent contact stimulates their leg hairs, triggering the release of hormones that cause them to cluster even closer.
• Pheromone Release: The gluttonous crowds produce vast amounts of poop, which carries a pheromone that further intensifies their transformation.
• Dietary Shift: The hoppers' diet changes to include plants with toxic alkaloids, making them poisonous to predators.
• Warning Colors: They develop a striking pattern that warns predators of their newfound toxicity.

These changes culminate in the formation of massive bands, sometimes millions strong, that decimate plant life across vast areas. Within a month, they can grow to 50 times their hatching weight.

The Gregarious Phase: A Plague Unleashed

The final metamorphosis sees the locusts take flight as a full-fledged swarm. These brightly colored, long-winged creatures are so different from their solitary counterparts that they were once believed to be a separate species.

A typical swarm can contain more locusts than there are humans on Earth, covering hundreds of square kilometers. Their numbers overwhelm predators, and their appetite is insatiable. A large swarm can consume the same amount of food as a city of millions, traveling up to 150 kilometers a day with the wind.

These swarms can even cross large bodies of water. In 1988, one swarm crossed the Atlantic Ocean, likely forming rafts to rest and even feeding on their dead to survive the journey.

When they find moist soil, the swarming mothers lay eggs, passing on their gregarious condition to the next generation, perpetuating the plague. A single plague can last for up to a decade.

The Human Cost of Locust Plagues

The regions inhabited by desert locusts are often the poorest in the world, where many people rely on subsistence farming. By destroying crops and pastures, these insects directly threaten the food security of 10% of the global population.

Combating the Plague: A Multi-Faceted Approach

Fortunately, locust plagues don't last forever. When the wet period ends, vegetation becomes scarce, and egg-laying conditions decline. As swarms die off, new hatchlings spread out, preventing the transformation into the gregarious phase.

Human intervention also plays a crucial role:

• Satellite Imagery: Researchers use satellite imagery to identify at-risk regions and alert local governments.
• Insecticides: Many countries use chemical insecticides to combat locusts.
• Fungal Diseases: Some regions have found success with fungal diseases that are lethal to locusts but safe for humans and the environment.

However, modern practices are exacerbating the threat. Monoculture farming provides a feast for locusts, and erratic weather patterns caused by climate change make swarms harder to predict.

A Call to Action

To prevent future locust plagues, we must:

• Cut carbon emissions to mitigate climate change.
• Rethink our agricultural practices to promote biodiversity.
• Reconsider our own consumption habits.

By addressing these issues, we can help prevent lonely locusts from transforming into catastrophic crowds, safeguarding the livelihoods of millions.