A locust is a type of short-horned grasshopper known for its ability to change its behavior and physical form. These insects shift from a solitary existence to a gregarious, swarming phase under specific environmental conditions, often related to population density.
Adult Locust: A Detailed Look
An adult locust possesses a body divided into three primary sections: the head, thorax, and abdomen. The entire body is covered by a tough exoskeleton made of chitin, providing protection and structural support. Adult locusts typically range from 2 to 6 centimeters (about 0.8 to 2.4 inches) in length, though dimensions vary by species and phase. For instance, the Desert Locust (Schistocerca gregaria) can measure between 5 to 8 cm (1.97 to 3.15 inches) long.
The head features large compound eyes, providing a wide field of vision, and short antennae for sensing odors and environmental cues. Strong mandibles are present for chewing plant material. The robust thorax is segmented and serves as the attachment point for three pairs of legs and two pairs of wings. The hind legs are larger and muscular, enabling powerful jumps, while the forewings are narrow and leathery, and the hindwings are broader and membranous. The abdomen is segmented, containing spiracles for breathing, and in females, it includes an ovipositor for laying eggs.
The coloration of adult locusts varies by phase. In their solitary phase, locusts often appear green or brown for camouflage. When transitioning to the gregarious (swarming) phase, their appearance changes. Gregarious adults may develop a more striking coloration, such as yellowish bodies with black stripes, or even bright yellow in mature males. This color change responds to increased population density.
Locust vs. Grasshopper: Key Differences
While all locusts are a type of short-horned grasshopper, not all grasshoppers exhibit the characteristics that define a locust. Both belong to the family Acrididae and share a similar basic body plan, including powerful hind legs for jumping. The primary distinction lies in the locust’s capacity for phase transformation, an ability to alter its morphology and behavior in response to population density.
This phase change leads to physical differences. In their gregarious phase, locusts develop stronger wings, suited for sustained, long-distance flight, unlike most localized grasshoppers. Their coloration also undergoes a shift; solitary grasshoppers and locusts typically have green or brown camouflage, while gregarious locusts display contrasting, vibrant colors like black, yellow, or orange. Gregarious locusts may develop more robust bodies, broader shoulders, and longer wings than their solitary counterparts, and their sexual dimorphism may become less pronounced.
Appearance Through Life Stages
A locust undergoes incomplete metamorphosis, with a life cycle of three main stages: egg, nymph (also called hopper), and adult. There is no pupal stage. The female locust lays her eggs in clusters, called egg pods, in moist soil, 2 to 10 centimeters deep. Buried and covered with a frothy liquid for protection, these eggs are not externally visible.
After hatching, wingless nymphs emerge, resembling smaller adults. These hoppers grow through a series of molts, shedding their exoskeleton multiple times in stages called instars. Each molt increases nymph size, and wing pads develop. Nymphs also change color by phase; solitary nymphs are green or brown, while gregarious nymphs display striking black, yellow, or orange markings. The final molt marks the transition to the adult stage, where the locust develops fully formed wings and reaches reproductive maturity.