Grasshoppers are common jumping insects, part of the order Orthoptera, often seen hopping through fields and gardens. Locusts are known for devastating crops in swarms. This difference often causes confusion about their relationship. This article clarifies the connection, explaining the biological transformation involved.
Understanding the Connection
Locusts are a specific type of grasshopper, but not all grasshoppers can transform into the swarming, gregarious phase characteristic of locusts. Both belong to the Acrididae family, known as short-horned grasshoppers. The distinction between a typical grasshopper and a locust is their behavioral plasticity and capacity for a dramatic “phase change” under specific environmental conditions.
How Locusts Are Different
When certain grasshopper species become locusts, they undergo significant physical and behavioral transformations, a phenomenon known as “phase polyphenism.” In their solitary phase, these insects resemble typical grasshoppers, blending into their environment with green or brown coloration and exhibiting shy, independent behavior. In the gregarious, or locust, phase, their appearance changes dramatically; they become darker, developing more robust bodies, larger and stronger wings suited for long-distance migration, and sometimes an orange head with dark spots.
Behaviorally, the shift is even more profound. Solitary grasshoppers avoid contact, while gregarious locusts become highly social, forming dense groups called bands (as nymphs) and swarms (as adults). They exhibit increased activity and a strong migratory drive, moving in unison across landscapes. This collective movement allows them to travel vast distances, a stark contrast to their sedentary solitary counterparts.
The Triggers of Swarming
The transformation from a solitary grasshopper to a gregarious locust is initiated by environmental and biological triggers. Prolonged drought followed by heavy rains creates ideal conditions for rapid vegetation growth, leading to a sudden increase in grasshopper populations. This increased density causes individuals to come into frequent physical contact.
Physical contact, particularly jostling of their hind legs, along with the sight and smell of other grasshoppers, stimulates serotonin production in their brains. This serotonin increase triggers the physiological and behavioral changes associated with the gregarious phase. Serotonin makes locusts mutually attracted, prompting them to aggregate and form cohesive groups. As more individuals join, small bands of nymphs merge into larger swarms of winged adults, capable of moving great distances and consuming large amounts of vegetation. The behavioral change can occur rapidly, within hours of crowding.
Why the Distinction Matters
Understanding the difference between common grasshoppers and swarming locusts is important due to the agricultural and economic consequences of locust outbreaks. While solitary grasshoppers are generally harmless and play a role in ecosystems, locust swarms cause widespread damage to crops and pastures. A single swarm, potentially containing billions of insects, can consume the same amount of food as tens of thousands of people in a single day, leading to severe food insecurity and economic losses.
Historical records, dating back to ancient Egypt, document the severe impact of locust plagues on civilizations. Modern outbreaks continue to threaten global food security, particularly in vulnerable regions. Recognizing the specific conditions and biological mechanisms that trigger swarming allows for better monitoring, prediction, and management strategies to reduce the destructive potential of these insects.