It is a common misconception that locusts and cicadas are the same insect, largely due to their occasional appearance in large numbers and the prominent sounds they produce. However, these two insects are distinct, belonging to different scientific classifications and exhibiting unique biological and behavioral traits.
What is a Locust?
A locust is a type of short-horned grasshopper belonging to the family Acrididae within the order Orthoptera. They typically have a slender body, often green or brown, with large hind legs adapted for jumping. Locusts are herbivorous, feeding on a wide range of plants, including agricultural crops.
A defining characteristic of locusts is their ability to transform from a solitary phase to a gregarious, swarming phase under specific environmental conditions, such as increased population density and food scarcity. This phase change involves alterations in their behavior, physiology, and appearance, leading to the formation of destructive swarms. These swarms can travel vast distances, consuming vegetation and posing a threat to agriculture.
What is a Cicada?
Cicadas are insects classified in the order Hemiptera, distinguishing them as true bugs. They have stout bodies, prominent, widely spaced eyes, and clear, membranous wings. Cicadas feed on plant sap using piercing-sucking mouthparts.
The life cycle of a cicada is notable for its long nymphal stage, where they live underground, feeding on xylem fluids from tree roots. This subterranean period can last from two to eight years for annual cicadas, and 13 or 17 years for periodical cicadas, which emerge in synchronized, large numbers. Male cicadas produce loud sounds using specialized organs called tymbals to attract mates.
Key Distinctions
Locusts and cicadas diverge significantly in their biological classification, physical attributes, sound production mechanisms, life cycles, and overall ecological impact. These differences underscore why they are not the same insect.
Cicadas belong to the order Hemiptera, while locusts are part of the order Orthoptera. This taxonomic difference means they are not closely related. In appearance, locusts possess an elongated body with powerful hind legs for jumping and opaque wings. Cicadas have stouter bodies, larger heads with prominent eyes, and clear, membranous wings.
The way these insects produce sound is also fundamentally different. Male cicadas generate loud calls using tymbals, ribbed membranes on their abdomen that rapidly buckle inward and outward, creating a continuous buzzing or clicking sound. Locusts, in contrast, produce sounds through stridulation, rubbing body parts together, such as their hind legs against their wings, resulting in softer chirping or buzzing noises.
Their life cycles present another clear distinction. Locusts typically have a shorter life cycle, with eggs hatching into nymphs that become winged adults within a single year. Cicada nymphs spend years underground, sometimes over a decade, before emerging as adults to mate and lay eggs. Finally, their behavior and impact on the environment differ greatly. Locusts are known for their destructive swarming behavior, consuming entire crops and causing widespread agricultural damage. Cicadas, while emerging in large numbers, do not typically swarm destructively and cause minimal feeding damage to plants.
Understanding the Confusion
The confusion between locusts and cicadas stems from shared superficial characteristics and historical factors. Both insects appear in large numbers; locusts form dense, migratory swarms, while periodical cicadas emerge en masse.
Both also produce prominent sounds, contributing to the auditory landscape of summer. Historically, early European settlers in North America encountered periodical cicadas emerging in vast numbers and mistakenly referred to them as “locusts,” drawing parallels to the biblical plagues of locusts they were familiar with. This misnomer, such as calling periodical cicadas “17-year locusts,” has been passed down through generations, contributing to the enduring misunderstanding.