Grasshoppers and locusts are often confused due to their similar appearance, yet they are not entirely interchangeable despite sharing common ancestry. Understanding their relationship reveals unique distinctions.
The Core Distinction
All locusts are a specific type of grasshopper, but not all grasshoppers are locusts. They belong to the short-horned grasshopper family, Acrididae, and are distinguished by their ability to undergo a behavioral and physical transformation. This change allows them to transition from a solitary existence to forming massive, coordinated swarms. The term “locust” refers to a particular phase of certain grasshopper species, not a distinct biological classification.
Physical and Behavioral Differences
Grasshoppers lead solitary lives, blending into their environment with colors like green, brown, or gray. They are less mobile, primarily using their hind legs for jumping to escape threats. While grasshoppers possess wings, these are suited for shorter flights, keeping them localized within their habitats.
In contrast, locusts, particularly in their gregarious phase, exhibit distinct changes in appearance and conduct. They may develop brighter colors, often shifting to yellow or brown. Their bodies become more robust, and their wings grow longer and stronger, enabling sustained, long-distance migration. Behaviorally, solitary locusts resemble other grasshoppers, but gregarious locusts become active and are attracted to other individuals, moving in cohesive groups.
The Transformation to Locusts
The process by which certain grasshopper species become locusts is known as phase polyphenism, an example of phenotypic plasticity. This means a single genetic makeup can produce different observable traits depending on environmental factors. High population density is a primary trigger for this transformation, often occurring when abundant vegetation after a dry spell leads to increased numbers of grasshoppers congregating.
During this transition, physiological and behavioral changes occur rapidly. Physical contact among individuals, particularly touching their hind femora, is a stimulus that can increase serotonin levels, a neurotransmitter linked to these behavioral shifts. The insects shift from avoiding each other to becoming mutually attracted, and their brain chemistry adapts to facilitate gregarious behavior. This internal rewiring prepares them for collective movement and the formation of marching bands of nymphs or flying swarms of adults.
Ecological Roles and Impact
Grasshopper species play a role in ecosystems as herbivores, consuming plant biomass and contributing to nutrient cycling. They also serve as a food source for animals, including birds, reptiles, small mammals, and spiders. While they can occasionally cause localized plant damage, grasshopper populations do not pose a widespread threat to agricultural systems.
However, the impact of locust swarms is different. These swarms are destructive migratory pests globally, capable of consuming large amounts of vegetation. A single swarm, comprising millions of individuals, can devour the same amount of food in a day as tens of thousands of people. Their ability to travel long distances allows them to devastate crops and pastureland across wide regions, leading to food insecurity and economic losses.