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Cicadas and locusts are different insects. Cicadas are true bugs in the order Hemiptera; locusts are short-horned grasshoppers in the family Acrididae, within the order Orthoptera. Their sudden appearances can look similar, but a periodical cicada emergence is not a locust swarm, and the insects feed and affect plants in different ways.
The nickname “17-year locust” for an American periodical cicada is a historical common name, not a biological classification. This guide shows how to tell the two apart, explains why cicadas emerge in synchronized groups, and outlines what the distinction means for gardens, crops, and households with pets.
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| Name | Best for | Key spec | Checked |
|---|---|---|---|
| Cicada | Recognizing synchronized, above-ground adult emergences | Hemiptera; sucks plant fluids; periodical species emerge on 13- or 17-year schedules | November 2026 |
| Locust | Identifying grasshoppers capable of a swarming phase | Orthoptera, family Acrididae; chews vegetation; swarms can heavily damage crops | November 2026 |
The table is a broad comparison, not a promise that every member of either group behaves alike. “Cicada” includes many species, and the 13- and 17-year schedules apply to periodical cicadas. “Locust” refers to grasshoppers capable of a swarming phase; it does not mean every grasshopper is a locust or that every locust is always swarming.
What is the difference between a locust and a cicada?
The shortest accurate answer is taxonomy: a cicada is a true bug, while a locust is a grasshopper. The two belong to separate insect orders and have different feeding methods, life cycles, and relationships with plants.
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Cicadas belong to Hemiptera, the order that includes insects with piercing-and-sucking mouthparts. Locusts belong to Orthoptera, the grasshopper order; “locust” describes grasshopper species that can enter a swarming phase, not every grasshopper. The University of Wisconsin–La Crosse’s Cicadas 2024 explainer poses the same reader question because the common confusion is widespread.
That distinction matters more than a quick visual impression. A mass of insects can be startling whether it is made up of cicadas emerging from soil or locusts feeding across vegetation. But size of the group alone does not establish its identity. The useful clues are the insect group, how it feeds, and whether the appearance fits a periodical emergence or a locust swarming phase.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware match| Feature | Cicada | Locust |
|---|---|---|
| Insect group | True bug, order Hemiptera | Short-horned grasshopper, family Acrididae, order Orthoptera |
| Feeding | Sucks plant fluids | Chews vegetation |
| Mass appearance | Some periodical species emerge together after 13 or 17 years underground | A swarming phase can produce large, mobile groups |
| Plant effect | Usually minimal damage according to North Carolina Cooperative Extension, although circumstances vary | Swarms can heavily damage crops |
| Sound evidence in the sources | Male cicadas produce sound with tymbals | The official sources cited here do not support one general sound description for every locust |
Why are cicadas sometimes called “17-year locusts”?
“17-year locust” is an inaccurate nickname for a periodical cicada. It refers to the striking emergence of some North American cicadas after 17 years underground, but the insects are not locusts and are not grasshoppers.
Some periodical cicadas follow a 13-year schedule and others a 17-year schedule, as the Smithsonian National Museum of Natural History’s Periodical Cicadas resource explains. The number describes the interval between synchronized adult emergences for those periodical species; it does not describe all cicadas. Many cicada species do not use either of those schedules.
The nickname persists because a large emergence can blanket trees and the ground with insects, much as a locust swarm creates a memorable spectacle. Biologically, however, the events have different causes and consequences: cicadas are completing a long underground development, while locusts are grasshoppers expressing a swarming phase.
When using the name, make the distinction explicit. “Periodical cicada” identifies the insect accurately; “17-year locust” is a colloquial label that can mislead readers into picturing a grasshopper outbreak. The nickname is useful to recognize when someone uses it, but it should not be treated as a scientific classification or as evidence that cicadas and locusts are closely interchangeable.
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Periodical cicadas spend most of their lives underground as nymphs, feeding on sap from tree roots. When the scheduled emergence arrives, they come out together, mature into winged adults, mate, and reproduce. The Smithsonian reports that periodical cicada adults live about three to four weeks.
After mating, female cicadas lay eggs in branches. The young nymphs hatch and return to the soil, where they begin the long underground stage again. This synchronized cycle explains why a quiet area can suddenly produce thousands of adult cicadas within a short period.
The cycle has a clear sequence: underground nymphs feed on root sap; adults emerge; adults mate; females lay eggs in branches; and the next young nymphs return to the soil. The adult phase is brief compared with the long period spent underground, so a conspicuous emergence is a concentrated reproductive stage rather than a permanent change in the local insect population.
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Locusts are grasshoppers, so their development is not the same periodical underground cycle. The official descriptions from the Indiana Department of Natural Resources and Ohio State University Extension support identifying locusts as grasshoppers capable of a swarming phase, but they do not establish one universal timetable for all locust species. A locust outbreak and a cicada emergence therefore should not be treated as interchangeable events.
What “synchronized” means for cicadas
Synchronization means that many individuals of the same periodical brood emerge during the same general window. The insects did not arrive from somewhere else as a moving swarm; they developed locally in soil and surfaced when their cycle reached its endpoint. Their numbers make the emergence conspicuous, but the biological process is still a cicada life cycle.
The 13- and 17-year figures are not a forecast for every place or every cicada. They describe the schedules of periodical species. If someone sees cicadas in a different year, that alone does not contradict the schedule: the broad group includes species beyond those periodical cicadas, and the schedules should not be generalized beyond their scope.
How do cicadas and locusts feed?
Cicadas use piercing-and-sucking mouthparts to take plant fluids. Their nymphs feed on sap from roots underground, while adults feed on plant fluids above ground. They do not chew leaves in the manner of a grasshopper.
Locusts chew vegetation. When locusts enter a swarming phase, many insects may feed in the same area, increasing the amount of plant material removed. This difference in feeding explains why a mass of cicadas can look alarming without producing the same crop-loss pattern associated with a damaging locust swarm.
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“Plant fluids” and “vegetation” are broad categories, so the exact host plants and severity depend on the species and setting. It is safer to identify the insect than to infer its impact solely from the size of the group. A large number of insects is a reason to look closely, not a reason to assume that the plants are being damaged in the same way.
Do cicadas damage plants as much as locusts?
Generally, no. North Carolina Cooperative Extension’s May 18, 2021, guidance describes cicadas as causing minimal plant damage, whereas locust swarms can heavily damage crops. That is a broad comparison, not a guarantee that every cicada species or every locust species behaves identically in every garden.
Cicada damage is associated with feeding on plant fluids and with females placing eggs in branches. Young trees and vulnerable branches may deserve closer observation during a major emergence, but the extension guidance does not support portraying periodical cicadas as an agricultural equivalent of locusts.
Locust damage is potentially much more serious when a swarm feeds across cropland. The relevant risk is the amount of vegetation being chewed by a large number of grasshoppers. If plants are being stripped rapidly, document the insects and contact a local cooperative extension or agricultural authority for species-specific advice rather than assuming the insects are cicadas.
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For a household or gardener, the practical takeaway is to distinguish visible abundance from plant injury. Cicadas may be conspicuous and numerous while causing minimal damage overall; a locust group moving through and chewing vegetation raises a different concern. The broad comparison does not supply a treatment threshold or a universal remedy, so a local expert is more useful than a one-size-fits-all response when crops or valued plants are at stake.
Can you identify them by sound?
A loud, sustained chorus is a useful clue for cicadas, and the mechanism is distinctive: male cicadas make sound with tymbals, membranes on their bodies. The Ohio State University Extension’s 2025 periodical cicada fact sheet describes this cicada sound mechanism.
Do not turn that clue into an overconfident rule about locusts. The official sources cited here do not provide a complete sound comparison across all locust species, so there is no reliable, source-supported statement that every locust is quiet or that every species produces one particular call. Use sound together with the insect’s appearance, feeding behavior, and emergence pattern.
In other words, the tymbals tell you how male cicadas produce sound; they do not make sound alone a complete identification test. A chorus may help you recognize a cicada emergence, but if the distinction affects crop protection or another practical decision, confirm it with more than one clue.
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How can you identify a cicada or locust outdoors?
Use several clues rather than relying on the number of insects alone. A practical identification sequence is:
- Start with the setting. Insects emerging from soil around trees after a long, synchronized interval suggest periodical cicadas. A mobile group moving through vegetation and feeding heavily is more consistent with a locust swarming phase.
- Check the feeding evidence. Sap-feeding points toward cicadas; obvious chewing of leaves or other vegetation points toward locusts.
- Listen, but do not rely on sound alone. A loud male cicada chorus is compatible with tymbal-produced cicada calls. Lack of a familiar chorus does not, by itself, prove that an insect is a locust.
- Look for the life stage. Periodical cicada nymphs spend most of their lives underground and adults are present for only about three to four weeks. A group that appears as winged adults after a long underground interval fits this pattern.
- Confirm the group. If the identification matters for crop protection, pet exposure, or pesticide decisions, photograph the insect and ask a local extension service, natural-history museum, or qualified entomologist.
It helps to record context alongside a photograph: where you found the insect, whether it was on a tree or among vegetation, whether it was feeding, and whether many others appeared at the same time. Those observations connect the insect to the distinctions that matter here—feeding method, emergence pattern, and potential plant impact—without relying on a common name alone.
A general field guide can be an optional aid, especially when you need to compare several grasshopper and cicada species. A guide should support, not replace, local expert identification when plants or animals could be affected. No particular book or product is necessary for the basic comparison; the reliable starting point is the group and behavior, followed by expert confirmation if the decision has consequences.
How many cicada species are there?
The Indiana Department of Natural Resources gives an approximate figure of about 3,000 cicada species worldwide. Treat that as a contextual estimate rather than a permanently fixed count: species inventories and classifications can change, and the figure includes cicadas beyond the periodical species famous for 13- or 17-year emergences.
This diversity is another reason not to generalize from one dramatic emergence to every cicada. “Cicada” is a broad group, while “periodical cicada” refers to the particular species and broods with synchronized 13- or 17-year schedules. The estimate is not a count of periodical species and does not say how many cicadas occur in a particular region.
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What should pet owners know about cicadas and locusts?
For a pet owner, the first practical step is accurate identification. A mass of insects near a yard, kennel, or walking route may be a periodical cicada emergence rather than a locust outbreak, and the appropriate plant-management response can differ substantially.
The official sources discussed here address cicada identification, life cycle, sound, and plant impact; they do not establish a universal toxicity rule for pets. Do not infer that an insect is safe or unsafe for a particular animal simply from its name or from the size of the emergence. If a pet has eaten an unknown insect and seems unwell, contact a veterinarian and share a photograph or specimen only if it can be collected safely.
Do not apply an insecticide around pets simply because many insects are present. Read the product label and follow local veterinary or extension guidance before using any chemical near animals, food bowls, bedding, or outdoor enclosures. Keep pets away from treated vegetation and from any area where a pest-control product is being applied. These precautions do not depend on confusing cicadas with locusts; the identification itself does not settle an animal’s individual health risk.
Is a large cicada emergence the same as a locust swarm?
No. Both can involve conspicuous numbers, but the underlying biology is different. Periodical cicadas emerge from underground on a brood schedule, while locusts are grasshoppers that can enter a swarming phase.
A cicada emergence is therefore best understood as a synchronized appearance of adults from a local underground population. A locust swarm is a mass phase of a grasshopper capable of moving and feeding as a group. Similar visual drama does not make the two events taxonomically or ecologically equivalent.
The distinction also helps explain why the right response can differ. If cicadas emerge around trees, the event fits the insects’ development and reproduction cycle. If a group is moving through vegetation and causing substantial chewing damage, it is more important to obtain local identification and crop advice. Neither the shared abundance nor the nickname “17-year locust” is enough to classify what you are seeing.
What common mistakes should you avoid?
- Calling every mass of insects a swarm. A large cicada emergence is not automatically a locust swarm.
- Using “17-year locust” as a scientific name. The term is a colloquial label for certain periodical cicadas.
- Assuming every cicada follows a 13- or 17-year cycle. Those intervals apply specifically to periodical cicadas.
- Expecting identical plant damage. Cicadas suck plant fluids and are generally associated with minimal damage; locust swarms chew vegetation and can heavily damage crops.
- Identifying by noise alone. Tymbals explain male cicada sound, but official sources do not establish one universal locust sound profile.
- Assuming one species represents the whole group. Both names cover multiple species, and local conditions matter.
- Treating a common name as a diagnosis. “Locust” in “17-year locust” does not mean the insect is a grasshopper.
What is the simplest way to explain the difference?
Use this sentence: “A cicada is a sap-feeding true bug that may emerge on a long underground schedule; a locust is a vegetation-chewing grasshopper that can enter a swarming phase.” It captures the taxonomic, feeding, and behavioral distinctions without implying that every cicada is periodical or every grasshopper is a locust.
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How should you respond when you find one?
For a single insect, observe it without handling it unnecessarily and note where it was found, what it was feeding on, and whether it was underground, on a tree, or moving through vegetation. For a large group, photograph representative individuals and the plant damage, then seek local identification before taking control measures.
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Most importantly, match the response to the insect. A periodical cicada emergence is a temporary, synchronized life-stage event; a locust problem may require crop-protection advice because feeding by a swarm can be substantially more damaging. Local extension services are the appropriate source for decisions that depend on species, crop, and geography.
The comparison is not a substitute for a local outbreak forecast or a species-by-species assessment. It does provide a useful first screen: identify whether the insect is a true bug or a grasshopper, note whether it is sucking fluids or chewing vegetation, and then seek local help if the plants are being damaged or a control decision is needed.
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Frequently Asked Questions
Are cicadas dangerous to dogs and cats?
The official sources cited here establish cicada classification and feeding biology, not a universal toxicity rule for pets. If a dog or cat eats an unknown insect and then appears unwell, contact a veterinarian and identify the insect with a photo if possible.
Do all locusts form swarms?
“Locust” refers to grasshoppers capable of a swarming phase, but the term does not mean that every individual is always in a swarm. Swarming behavior is a phase, so local species and conditions determine what you observe.
Why do cicadas appear every 13 or 17 years?
Those intervals are the schedules documented for periodical cicadas, whose nymphs spend most of their development underground. They emerge together, reproduce, and begin the next generation; the schedules should not be applied to every cicada species.
How long do adult periodical cicadas live?
The Smithsonian National Museum of Natural History says periodical cicada adults live about three to four weeks. That short adult stage follows the much longer underground nymph stage.
Are cicadas and locusts both grasshoppers?
No. Cicadas are true bugs in the order Hemiptera. Locusts are short-horned grasshoppers in the family Acrididae, within Orthoptera.
The Bottom Line
Bottom line: Cicadas are sap-feeding true bugs; locusts are vegetation-chewing grasshoppers that can swarm. Periodical cicadas may emerge together after 13 or 17 years underground, but that synchronized appearance is not a locust swarm. The “17-year locust” is only a nickname.
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