A locust is not a separate species of insect but a particular phase that certain short-horned grasshoppers can enter. This transformation, known as phase polymorphism, turns a solitary insect into a highly mobile, gregarious creature capable of forming massive swarms. Therefore, the appearance of a locust is highly variable, reflecting its current life stage and social environment.
Fundamental Physical Characteristics of an Adult Locust
The adult locust is structured into three regions: the head, thorax, and abdomen. The head features large compound eyes, providing a wide field of vision important for swarm coordination. Locusts possess relatively short antennae, a characteristic placing them within the suborder Caelifera, the short-horned grasshoppers.
The thorax is the attachment point for the six legs and two pairs of wings. The hind legs are noticeably larger and more muscular, adapted specifically for powerful jumping. Most fully developed adults measure between 1.5 to 3 inches (4 to 8 centimeters) in length, though size varies significantly between species and phases. Fully developed wings typically extend beyond the abdomen, providing the necessary lift for sustained, long-distance flight.
Distinguishing Locusts from Common Grasshoppers
While all locusts are technically grasshoppers, their appearance in the swarming phase develops specific visual features. The most apparent difference is the development of longer and stronger wings in locusts, necessary to support migratory behavior. A locust’s wing structure is built for covering hundreds of miles, unlike grasshoppers which fly short distances.
When the insect enters the gregarious phase, the overall body shape becomes more standardized and robust. This includes a shift in the shape of the pronotum, the saddle-like shield covering the thorax. In the gregarious form, this shield becomes more uniform and saddle-shaped, contrasting with the variable pronotum of solitary grasshoppers. Furthermore, swarming locusts adopt a conspicuous, uniform coloration, unlike grasshoppers that blend into their environment with green or brown coloring.
Appearance Changes Based on Life Stage and Phase
The most dramatic visual differences are tied to the locust’s developmental stage and population density phase. Nymphs, or “hoppers,” are the young, wingless stage and look very different from adults. Solitary-phase nymphs are typically cryptic, displaying colors like green or straw-brown to camouflage against vegetation.
When population density increases, the insect enters the gregarious phase. The coloration of gregarious nymphs is a striking contrast, often featuring a bold pattern of black and bright yellow or orange. This aposematic, or warning, coloration signals to predators that the insect may be unpalatable. These hoppers also become highly synchronized, moving together in dense, visible bands.
Adult locusts continue this phenotypic plasticity. Gregarious adults develop a larger head capsule and a body optimized for flight, often displaying a bright, uniform yellow or reddish-brown color. This transformation is driven by hormonal changes accompanying crowding. Solitary adults maintain camouflage, remaining a dull green or brown to match their habitat. This shift from cryptic to conspicuous aids in group cohesion and provides a visual marker of the highly mobile swarms.