The terms “locust” and “grasshopper” are often used interchangeably, causing confusion. While related, a crucial distinction separates them. Understanding this difference involves their biological classifications and unique adaptations.
The Grasshopper-Locust Connection
All locusts are a specific type of grasshopper. Both belong to the order Orthoptera, which includes grasshoppers, crickets, and katydids. Locusts are classified within the family Acrididae, known as short-horned grasshoppers. This means that while every locust is a grasshopper, not all grasshoppers possess the characteristics that define a locust.
The distinction between a “grasshopper” and a “locust” is not taxonomic, but behavioral and morphological. Certain species within Acrididae exhibit the “locust” phenomenon, having evolved a unique ability to undergo a dramatic transformation, setting them apart from their more solitary grasshopper relatives.
Defining the Locust: Beyond the Grasshopper
What defines a locust is its ability to switch between two distinct phases: solitary and gregarious (swarming). This phenomenon, known as phase polyphenism, allows individuals with the same genetic makeup to display different physical and behavioral traits based on environmental cues. When population densities are low, locusts behave like typical grasshoppers, living solitary lives and avoiding others.
However, when conditions become crowded, often triggered by abundant rainfall and population growth, these grasshoppers undergo a rapid transformation. Physical contact among individuals, particularly touching their hind legs, initiates this change, leading to increased serotonin levels in their brains. This neurochemical shift drives a behavioral change, making them attracted to other locusts rather than repelled.
The transformation involves behavioral shifts, and changes in morphology and physiology. Gregarious locusts develop larger, stronger muscles and longer wings, preparing them for sustained flight and migration. Their coloration also changes, becoming more vibrant and conspicuous, unlike the duller colors of their solitary counterparts. These combined changes enable them to form dense, cohesive groups that can travel vast distances.
The Devastating Power of Swarms
The unique ability of locusts to form massive swarms has devastating consequences, particularly for agriculture and food security. A single swarm, ranging from less than one to over 1,000 square kilometers, can contain tens of millions to hundreds of millions of individual locusts. These swarms are highly mobile, capable of flying up to 150 kilometers per day with favorable winds.
The destructive potential lies in their voracious appetite; a single locust can consume its own weight in fresh food daily. A small swarm of just one square kilometer can eat the same amount of food as 35,000 people in one day. This consumption leads to widespread devastation of crops and pastureland, threatening livelihoods and exacerbating food shortages in affected regions. For instance, a major outbreak between 2019 and 2022 severely impacted East Africa, the Arabian Peninsula, and the Indian subcontinent, with some areas experiencing 100% crop losses. Controlling these swarms is challenging due to their migratory nature and rapid reproduction, often requiring aerial and ground spraying of pesticides.