Locusts and cicadas are entirely different insects that belong to separate biological orders and share almost nothing in common beyond the fact that both can appear in enormous numbers. Locusts are a type of grasshopper in the order Orthoptera, while cicadas are true bugs in the order Hemiptera. The confusion between them is largely a naming accident: in parts of the United States, periodical cicadas have been called “locusts” for centuries, a misnomer that stuck. Once you look at how these insects are built, what they eat, how they make noise, and how they live, the gulf between them becomes hard to miss.
Why People Mix Them Up
The mix-up is almost entirely an English-language problem rooted in colonial American history. When European settlers first encountered the mass emergences of periodical cicadas, the sheer number of insects reminded them of the biblical plagues of locusts. They started calling cicadas “locusts,” and the label persisted. To this day, people refer to Brood X or other periodical cicada emergences as “locust years.” If you grew up hearing your parents call cicadas “locusts,” the two names can feel interchangeable. They are not. A locust is a grasshopper that has entered a swarming phase. A cicada is a sap-feeding bug with a long underground development period. They are about as closely related to each other as a dog is to a lizard.
Completely Different Body Plans
The easiest way to tell the two apart is to look at them. Locusts have the classic grasshopper body: large hind legs built for jumping, chewing mouthparts with visible mandibles, and relatively short antennae. They look like what they are, which is grasshoppers that happen to form swarms under certain conditions. Cicadas, on the other hand, have stout, wide-set bodies with large transparent wings, prominent compound eyes set far apart on a broad head, and no powerful jumping legs. Their most distinctive anatomical feature is their mouthpart: a needle-like stylet that pierces plant tissue so the cicada can drink xylem sap. Research on cicada mouthparts has shown that the tips of their mandibular stylets are reinforced with higher levels of hardness and stiffness compared to the rest of the structure, an adaptation for puncturing tough woody stems.1PubMed Central. Comparative Material and Mechanical Properties among Cicada Mouthparts: Cuticle Enhanced with Inorganic Elements Facilitates Piercing through Woody Stems for Feeding Locusts chew leaves, stems, and virtually any green plant material with their jaws. The feeding strategies could not be more different: one pierces, the other grinds.
How Each One Makes Noise
Both insects are associated with loud sounds, but they produce them through completely different mechanisms. Male cicadas generate their calls using specialized structures called tymbals, which are ribbed membranes on the sides of the abdomen. Muscles rapidly buckle these membranes inward and outward, and a largely hollow abdomen acts as a resonating chamber that amplifies the click into the loud, buzzing drone that defines summer in many parts of the world. Some cicada species can produce calls exceeding 100 decibels at close range, roughly as loud as a chainsaw.
Locusts and their grasshopper relatives make sound through stridulation, which essentially means rubbing two body parts together. Many species scrape a row of small pegs on the inner surface of their hind legs against a thickened vein on the forewing. The result is a quieter, raspier chirp or buzz, nothing like the sustained electrical-sounding whine of a cicada. The evolutionary lineage that includes grasshoppers, crickets, and katydids (the order Orthoptera) has been producing sound for an extraordinarily long time; phylogenomic analyses place the origin of crown Orthoptera at roughly 355 million years ago, deep in the Carboniferous period.2Nature Communications. Phylogenomic analysis sheds light on the evolutionary pathways towards acoustic communication in Orthoptera Cicadas evolved their tymbal system independently and much later in a completely separate insect lineage.
Dramatically Different Life Cycles
This is where the two insects diverge most spectacularly. Most locust species have relatively short life cycles. The desert locust, for example, can go from egg to flying adult in a few months under warm conditions. Females lay eggs in the soil, nymphs hatch and pass through several molts above ground, and within weeks the population can explode if conditions are right. Some locust species do have a dormancy strategy: parental experience of shortening day length can trigger embryonic diapause in the eggs, with diapause rates reaching as high as about 87% when parents experienced significant photoperiod decline.3Journal of Insect Physiology. Embryonic diapause in the Australian plague locust relative to parental experience of cumulative photophase decline But even with diapause, locusts do not spend years underground. Their world is the surface.
Cicadas, by contrast, are defined by their underground phase. After hatching from eggs laid in tree branches, tiny cicada nymphs drop to the ground and burrow into the soil, where they attach to tree roots and feed on xylem fluid. Annual cicada species spend two to five years underground before emerging, molting into winged adults, mating, and dying within a few weeks. The periodical cicadas of eastern North America take this to an extreme: they stay underground for either 13 or 17 years, depending on the species. Those prime-numbered cycles are not random. Modeling work suggests that prime-numbered life cycles are favored because they help periodical cicada populations avoid hybridizing with broods on different schedules. Hybrids that emerge out of sync with either parent population lack the safety of mass numbers and are more vulnerable to predators.4PubMed Central. Hybridization selects for prime-numbered life cycles in Magicicada: An individual-based simulation model of a structured periodical cicada population
The adult phase of a cicada’s life is strikingly brief compared to the years spent underground. Males call, females mate and lay eggs, and within a matter of weeks the adults are dead. Locusts, by contrast, spend their entire active lives above ground eating, moving, and (in swarming species) migrating.
The Locust Phase Change
One of the most remarkable things about locusts is that a “locust” is not always a locust. Most locust species exist in a solitary form that looks and behaves like an ordinary, harmless grasshopper. Under certain environmental triggers, primarily crowding, these insects undergo a dramatic transformation into a gregarious phase in which they change color, alter their body proportions, become more active, and aggregate into swarms that can number in the billions. Desert locusts can shift between these solitarious and gregarious forms, and the transformation involves widespread changes in behavior, physiology, and body shape, triggered by the presence or absence of other locusts.5PubMed. Substantial changes in central nervous system neurotransmitters and neuromodulators accompany phase change in the locust Some behavioral changes can happen within hours, while the full morphological transformation can take generations.5PubMed. Substantial changes in central nervous system neurotransmitters and neuromodulators accompany phase change in the locust
Crowding is the central trigger. When population densities rise, typically after rains produce abundant vegetation in arid regions, solitary grasshoppers are forced into closer and closer contact. This physical proximity biases the insects toward the gregarious form.6PubMed Central. Locust dynamics: behavioral phase change and swarming Once enough individuals switch, the swarm takes on a life of its own, moving collectively across landscapes and devastating crops in its path. This phase-change ability is what separates locusts from ordinary grasshoppers, and it has no parallel in cicadas. Cicadas emerge in massive numbers, but they do not aggregate and migrate as a coordinated swarm. Their mass emergence is a one-time event tied to their life cycle, not a behavioral phase they can switch in and out of.
How Far They Travel
Locusts in their gregarious phase are exceptional long-distance fliers. Swarms routinely cover hundreds of kilometers, riding winds and actively maintaining altitude for extended periods. The most dramatic documented case occurred in 1988, when a swarm of African desert locusts crossed the Atlantic Ocean from West Africa to the Caribbean, a nonstop flight of roughly 5,000 kilometers that lasted four to six days.7Quaternary International. Migration and trans-Atlantic flight of locusts That distance pushed the boundaries of what researchers thought locusts could physically manage, and it was wind-assisted, but the locusts still had to actively fly and keep themselves airborne for days on end.
Cicadas are mediocre fliers by comparison. Adults can fly, and they buzz clumsily between trees during mating season, but they do not migrate. A cicada’s flight range is typically measured in meters or at most a few hundred meters between trees within a neighborhood. They have no reason to fly far: their entire adult purpose is to mate and lay eggs near the trees they emerged from. If you are watching an insect swarm blotting out the sky and moving with purpose across a landscape, you are looking at locusts. If you are watching clumsy, noisy insects bumping into your porch light in June, those are cicadas.
What They Do to the Environment
The ecological footprints of the two insects are almost inverted. Locust swarms are one of the most destructive natural phenomena in agriculture. A single large swarm can contain tens of billions of individuals and consume in a day what tens of thousands of people would eat. They strip fields, orchards, and pastures bare. The economic and humanitarian damage from major locust outbreaks, particularly in East Africa, the Middle East, and South Asia, runs into the billions of dollars and can trigger food crises.
Cicadas, by contrast, are largely benign and even beneficial to their ecosystems. When billions of cicadas emerge, mate, and die within weeks, their carcasses create a massive pulse of nutrients. The decaying bodies deliver carbon and nitrogen into the soil, fueling microbial activity and enriching the ground around the trees the cicadas fed on for years.8Applied Soil Ecology. Cicada necrobiome mediates greenhouse and trace gas pulses following periodic mass emergence The most significant plant damage cicadas cause is not from feeding but from egg-laying: females slit small branches with their ovipositors to deposit eggs, which can cause twig dieback on young or ornamental trees. For established trees, this “flagging” of branch tips amounts to a natural pruning that rarely threatens the tree’s health. Compared to a locust swarm, cicada damage is trivial.
Locusts as Food
Locusts have been eaten by humans for thousands of years, and they remain an important food source in parts of Africa, the Middle East, and Asia. They are nutritionally dense, rich in protein, minerals, fiber, and fats. Research on desert locusts has found that their nutritional content varies depending on diet, with protein, fat, and energy levels shifting based on whether the locusts feed on legumes, cereals, or grasses. Locusts reared on a legume-based diet, for instance, showed higher protein and fat content, while those on a cereal diet had more carbohydrates.9African Journal of Tropical Entomology Research. Effects of diet on the nutritional composition of the desert locust Schistocerca gregaria (Orthoptera: Acrididae) The mineral profile tends to be high in magnesium and calcium across diets.9African Journal of Tropical Entomology Research. Effects of diet on the nutritional composition of the desert locust Schistocerca gregaria (Orthoptera: Acrididae) Interest in locusts as a sustainable protein source has grown in recent years, with researchers exploring the possibility of farming them on locally available feedstocks.
Cicadas are also edible and have been eaten in various cultures, particularly in China and parts of the southeastern United States, where periodical cicada emergences create a brief window of abundance. Freshly molted cicadas, still soft and pale before their exoskeleton hardens, are considered the best stage for eating. They are sometimes compared in flavor and texture to shrimp, which makes sense given that insects and crustaceans are both arthropods. People with shellfish allergies are generally advised to avoid eating cicadas for the same reason. The practice is more novelty than staple, though, because cicada emergences are infrequent and unpredictable in most regions.
A Quick Visual Field Guide
If you encounter a large insect and want to know which one you are looking at, a few features settle the question fast:
- Hind legs: Large, muscular, and obviously built for jumping means grasshopper or locust. Short and unremarkable means cicada.
- Wings at rest: Cicadas hold their wings tent-like over their body, and the wings are broad and often clear with visible veins. Locusts fold narrow wings along the body, with the forewings forming a leathery cover.
- Eyes: Cicadas have wide-set, bulging compound eyes on the sides of a broad head, plus three small simple eyes arranged in a triangle on top. Locusts have smaller, more forward-facing compound eyes on a narrower head.
- Sound: A sustained, pulsing electrical buzz or whine from the trees is almost certainly a cicada. A drier, scratchier chirp from grass or low vegetation is a grasshopper or locust.
- Season and setting: If you are in North America hearing a deafening chorus from the treetops in late spring or summer, you are hearing cicadas. Locust swarms are uncommon in North America; they are primarily a phenomenon of Africa, the Middle East, and parts of Asia and Australia.
Why the Confusion Persists
Beyond the old colonial misnaming, several other factors keep the confusion alive. Nature documentaries and news coverage sometimes use dramatic footage of locust swarms alongside stories about cicada emergences without clearly distinguishing the two events. Both involve huge numbers of insects appearing seemingly overnight, which is the kind of visual that tends to get lumped under a single “plague of bugs” mental category. Social media amplifies the problem: during a Brood XIX or Brood XIII cicada emergence, posts warning about “the locusts” spread quickly among people who have never seen either insect up close.
The word “locust” also appears in unrelated plant names, like the black locust tree and the honey locust tree. These trees got their names because early colonists associated them with the carob tree, sometimes called the “locust tree” in reference to the biblical food that sustained John the Baptist in the wilderness. The tangled etymology just adds another layer of confusion. Knowing that locusts are swarming grasshoppers and cicadas are underground-dwelling sap feeders in a completely different insect order is the single cleanest way to cut through all of it.