Is There a Difference Between a Cicada and a Locust?

Updated on September 14, 2018
Source

In spring and summer, when insects become active once again, two bugs that we sometimes hear about are cicadas and locusts—especially when there's a significant "swarm" expected. Sometimes, people use the two names interchangeably for what they think is the same insect. Is this acceptable, or is there a difference between a cicada and a locust?

Yes, Cicadas and Locusts Are Different

Cicadas and locusts are in fact different insects. They aren't even from the same order. They are often confused with each other due to their behavioral similarities. Locusts swarm, and cicadas—in particular, periodical cicadas—are often thought to swarm. However, cicadas don't actually swarm—they just happen to be above the ground in large numbers at the same time.

The association between cicadas and locusts goes back to colonial times. When periodical cicadas showed up in large numbers, the colonists assumed they were experiencing a "locust plague"—similar to the eighth plague of Egypt described in the Bible.

Cicada vs. Locust

Description
Cicada
Locust
Order
Hemiptera (True Bug)
Orthoptera
Family
Acrididae
Cicadoidea
Size
0.75–2.25 in (1.9–5.7 cm)
0.5–3 in (1.3–7.6 cm)
Diet
Tree sap
Leaves and other soft plant tissue
Life Span
Up to 17 years
Up to one year
Collective Name
Cloud or plague
Swarm
Distinguishing Features
Short body, large eyes, clear wings, larger front wings
Long body, larger rear wings, long hind legs
At a glance, cicadas and locusts can appear similar, but there are many differences between the two herbivorous insects.
A desert locust, the most widely known locust species.
A desert locust, the most widely known locust species. | Source

Locust or Grasshopper?

All locusts are grasshoppers, but not all grasshoppers are locusts.

What Is a Locust?

A locust is a grasshopper from the family Acrididae that has reached adulthood. Although they are sometimes referred to as different species, there is no taxonomical distinction between locust and grasshopper species. The only distinction is the swarming behavior.

Why Do Locusts Swarm?

Locusts are usually solitary, however, periods of wet weather can change things. The wet weather causes an increase in numbers, and then dry weather forces the insects closer together on the remaining vegetation.

A study published in Proceedings of the National Academy of Sciences in 2001 states that the frequent touching of the locusts' hind legs due to this forced crowding causes the swarming behavior.

In 2009, a study published in Science showed that serotonin levels significantly increased during the switch from solitary to gregarious behavior, while blocking serotonin activity prevented the formation of locust groups.

These findings suggest that the physical contact brought on by overcrowding causes the release of serotonin, which, in turn, promotes the swarming behavior.

Are Locust Swarms Dangerous?

Locusts won't bite you, they aren't poisonous or toxic, and there is no evidence that they carry any diseases. However, they can significantly damage crops—even as nymphs.

A swarm contains tens of millions of locusts that can eat their weight in food in just one day. This can severely cripple local farming economies and starve small populations.

When they run out of food in their area, they'll all fly together in a swarm to find something else to eat. They can travel up to 100 miles each day.

What Does a Locust Sound Like?

Locusts rub their wings together or against their body to create a soft buzzing sound. This sound can be amplified when millions are flying past, but locusts are not nearly as loud as cicadas.

Cicada
Cicada | Source

What Is a Cicada?

A cicada is an insect from the order Hemiptera (true bugs) and superfamily Cicadoidea. There are around 3,000 known species of cicadas, and they live throughout much of the world.

Are Cicadas Harmful?

Even though they generally are not harmful, they can be annoying to many people, mainly due to the noises they make. They don't sting, and they generally don't bite. However, they have been known to mistake a human for a tree, and it hurts if they poke you with their proboscis while looking for food.

Due to the huge numbers of cicadas that are active at once, the sound of a cicada invasion can be deafening. Those who live in an area with an emerging brood may wish to consider using earplugs or noise-canceling headphones during the weeks the insects are active.

Unlike locusts, cicadas don't destroy crops. They only feed on woody trees, so most farmers and gardeners have nothing to worry about. They lack the mouthparts needed to feed on fruits and flowers.

Why Do Cicadas Make So Much Noise?

The loud buzzing and clicking sounds you might have heard before are made by rapidly flexing and relaxing muscles to shake structures called tymbals. Males use these sounds as mating calls. Each cicada species has its own mating call. In some cicada species, the males will all sing together, and the sound can reach 120 decibels. The noise has an added benefit - it keeps away predators such as birds.

What Is the Life Cycle of a Cicada?

After the mating period, females will carve into twigs and branches to lay their eggs. When the eggs hatch, the nymphs fall to the ground, where they use their powerful front legs to burrow deep into the ground and look for roots from which to drink sap.

When Do Cicadas Emerge From the Ground?

Depending on the species, adult cicadas will emerge from the ground within 2–17 years. Annual cicadas have adults that emerge ever year. They are also known as "dog day" cicadas, since they are most common during the dog days of late summer. These cicadas are greenish in color and are heard more often than seen.

Periodical cicadas are the ones most often mistaken for locusts. The adults emerge all at once after several years underground. They show up earlier in the year than annual cicadas—in spring when the temperature of the soil eight inches below the ground reaches 63 oF (17 oC). When millions of cicadas are active at the same time, it can certainly seem like a swarm.

Why Do Some Cicadas Take 17 Years to Emerge?

Only cicadas from the genus Magicada have life cycles of either 13 or 17 years. Currently, scientists believe these prime-numbered cycles evolved to avoid predation and harsh living conditions. By waiting 13 or 17 years to come out, they never synch up with the life cycle of any one predator species (e.g. cicada killer wasps).

Cicadas in a particular region that have their life cycles synced up are grouped into a brood. In 2019, Brood VIII will emerge in eastern Ohio, western Pennsylvania, and northern West Virginia.

Cicada
Cicada | Source

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    • jenb0128 profile imageAUTHOR

      Jennifer Bridges 

      5 years ago from Michigan

      Thanks for reading and commenting, everyone!

      As far as the "17-year locusts" - yep, that term just came from the confusion between cicadas and locusts. Locusts live normal grasshopper lifespans (the lifespan varies from species to species, but it's usually around 5 - 6 months).

      @pstraubie48: Yes, those would be cicada "skins." I remember having a small collection of them when I was a kid. They were definitely so much fun to find! :)

    • SidKemp profile image

      Sid Kemp 

      5 years ago from Boca Raton, Florida (near Miami and Palm Beach)

      Thanks - this clarifies something I've been wondering about for a long-time. And I want to follow up on the question from AvianNotice - is it only cicadas who have the long periods (13 and 17 years). Or are there also things like 7-year and 17-year locusts?

    • aviannovice profile image

      Deb Hirt 

      5 years ago from Stillwater, OK

      This is a fabulous piece, Jen. It was very well done, and answers many questions? Now, where did the mention of the 17-year locust come from?

    • pstraubie48 profile image

      Patricia Scott 

      5 years ago from sunny Florida

      This is very interesting, well organized, and filled in some details that I need to know. If I am not mistaken, the fascinating outer covering of the cicada was what we would delight in finding around our property in the late summer. Would that be correct?

      I looked on google images and it seemed to be the same one.

      Thanks for sharing with us.

      Sending Angels to you this afternoon. :) ps

    • kashmir56 profile image

      Thomas Silvia 

      5 years ago from Massachusetts

      Hi Jen this is a very interesting and informative article, some of this information i did not know before, thanks for helping learn more about these little critters .

      Vote up and more !!!

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