FAQs
Amazing Periodical Cicada Facts:
What is a cicada?
A cicada is a large, herbivorous insect in the order Hemiptera. Cicadas have sucking mouthparts, which they use to feed on xylem sap. Cicadas (and all hemipterans) do not have larval and pupal life stages like butterflies and bees do; juvenile cicadas, called nymphs, look like small wingless adults.
What is a periodical cicada (genus Magicicada)?
Periodical cicadas emerge in the spring in massive numbers (as many as 1.5 million individuals per acre!) after spending 13 or 17 years underground across eastern North America. Periodical cicada emergences are geographically distinct; the ones that emerge in the same area and year are known as a brood. There are fifteen extant broods, and two extinct ones. Periodical cicadas are unique creatures found nowhere else on earth.
Why do periodical cicadas emerge in such large numbers at once?
When millions of individuals synchronize their massive emergence, their sheer numbers overwhelm their predators. This strange strategy is called predator satiation. Predators eat their fill and enough cicadas remain to perpetuate their species.
Why do they spend so much time underground?
There are multiple (potentially non-exclusive) hypotheses for this strategy. Long development times underground may prevent predator specialization, as most (if not all) predators will not survive until the next emergence. Longer development might also mean larger growth, allowing females to lay more eggs.
How do cicadas know it is time to emerge from the earth?
In the long-term, one hypothesis suggests that cicadas track time by sensing seasonal changes in the quality or quantity of nutrients, plant hormones, or other components of the xylem sap on which they feed. Another possibility is that they have a yet unknown internal molecular clock which enables them to track time. In the short term, when soil temperatures a foot or so underground reach 64 degrees Fahrenheit in the 13th or 17 year, cicadas emerge from the ground.
Why do broods emerge in 13 or 17 year cycles?
There are several hypotheses for this, centered around reducing their vulnerability to predators. In order to overwhelm their predators with high numbers and survive to reproduce, it is essential that periodical cicadas emerge at the same time. Mathematically, 13 and 17 year brood emergences only overlap with each other once every 221 years! This prevents hybridization between broods -- which could interfere with the timing of their emergence, reducing populations and making them much more susceptible to extirpation by predators.
Are there blue-eyed cicadas and is there a reward if you find one?
Yes, there are blue-eyed cicadas and other variants of eye color caused by mutations in the development of typical red eye pigments. No, unfortunately there is no reward for finding one other than excitement and joy.
Are there non-periodical cicadas?
Yes! There are many species of cicada worldwide. In North America, the “dog-day” or “annual” cicadas emerge in late summer and in much lower numbers. Instead of relying on predator satiation, they are masters of blending into their surroundings and evading predators with rapid flight. You have probably heard the annual cicadas, but you may have never seen a living one. Annual cicadas take only a few years to develop, but some emerge every year.
Are cicadas locusts?
No: locusts are a group of short horned grasshoppers that have a swarming phase in their lifecycle under certain environmental conditions including food shortages. The association of cicadas with locusts may have come from the massive numbers that appear during an emergence, kindling fears of locust plagues in biblical and historical records.
How do cicadas make their noise?
Male cicadas contract muscles to vibrate drumhead-like tymbal organs on their abdomen. This sound resonates and is amplified by hollow cavities inside of their bodies. Different species of cicada produce different songs.
How loud can cicadas be?
Cicadas can get as loud as 105 decibels! For reference, a lawn mower can be up to 100 decibels.
What is the cicada life cycle?
- Adult cicadas lay their eggs in young tree branches.
- After hatching, the nymphs drop from the tree branches and burrow into the soil. Underground, they feed on many types of plant roots as they develop.
- When the nymphs have matured, after 13 or 17 years they emerge from the soil and climb up vertical structures and molt into winged adults.
- The adult males sing to assemble other members of their species in one location to court females, mate, and repeat the cycle!
What do adults do when they emerge?
The adults will suck xylem sap from the branches of trees and shrubs, in order to sustain themselves above ground. They will spend time gathering in large numbers with the purpose of selecting a mate. After mating, the female will lay her eggs in the young branches of trees.
How many eggs do females lay?
Females lay between 400 and 600 eggs in batches of 20 to 30. The eggs are laid in young branches (typically the diameter of a pencil). The eggs hatch in about 6 to 8 weeks. Each periodical cicada species makes distinctive egg nests, and there can be different numbers of egg nests on a specific twig. The females may move from branch to branch, or even from tree to tree, in order to lay their eggs.
What eats cicadas?
Lots of animals eat cicadas! Many small mammals like skunks, raccoons, squirrels, and rodents eat cicadas as do amphibians, reptiles, birds, and fish -- even humans, and other insects eat cicadas!
How do periodical cicadas defend themselves?
Periodical cicadas’ defense against predation is to overwhelm predators with their sheer numbers in a given area. Predators will eat cicadas until they cannot eat anymore and the survivors then go on to reproduce. They may also drop from plants or fly away from predators.
How come they only come up in certain areas?
There are 15 broods of periodical cicadas that emerge in different geographical regions at intervals of 13 or 17 years. Almost every year there is a brood of cicadas that emerges somewhere in the eastern half of the United States. Cicada presence may be patchy based on historical changes in patterns of land use. Deforestation for agriculture or urbanization may eliminate local populations of cicadas. Patterns of glaciation in the eastern North America over millennia likely affected their distributions.
What is a brood?
A brood is a group of periodical cicadas that synchronously emerges in a geographical area in the same year. There are twelve 17-year broods, and three 13-year broods. Each brood is assigned a roman numeral to distinguish them from each other. For example, Brood X last appeared in 2004 and reappears in 2021 in the same locations.
Why have I never seen them before? I’ve lived here more than 17 years.
Not all areas will see cicadas. There distributions are patchy. The counties in Maryland in which Brood X cicadas have been reported include Allegany, Anne Arundel, Baltimore, Carroll, Cecil, Frederick, Garrett, Harford, Howard, Montgomery, Prince Georges, Washington. The District of Columbia will have cicadas as will parts of Virginia. Interestingly, cicadas will not emerge on the Eastern Shore. Perhaps, during changing periods of glaciation, these regions were inaccessible to cicadas.
Cicadas and People:
Are cicadas dangerous to humans?
Cicadas are not dangerous to people and do not sting or bite. They do have sucking mouthparts and may poke your hand if you were to hold one.
Can people eat cicadas?
They can! People do eat cicadas and there are many tasty recipes out there. You may need to use caution if you are allergic to seafood with an exoskeleton like shrimp or prawns and, if eating adults rather than nymphs, it is always best to remove the wings and legs first.
Can dogs and cats eat cicadas?
It is o.k. if your cat or dog eats a few cicadas, but too many may upset your pet’s stomach and cause vomiting, constipation and lethargy. It is best to limit the number of cicadas that your pet ingests.
I’m afraid of cicadas. Where can I go to avoid them and how long do I have to stay away?
Periodical cicadas will begin to emerge in mid-May and all cicada activity should be complete by mid to late June. Cicadas will emerge in Maryland, Washington D.C., Virginia and Delaware (along with 12 other states), but certain areas, like the eastern shore of Maryland, will not experience a cicada emergence.
If I hold a cicada, will it pee on me?
It might! If you stand beneath a tree full of cicadas or you hold a cicada in your hand, you may feel or see a clear liquid. Cicadas feed on xylem sap from woody plants and excrete a clear harmless liquid.
Will cicadas attract copperheads?
Many people are asking if Brood X will attract copperheads. To learn the answer see the article "Copperheads and Cicadas" written by Ray Bosmans, from the University of Maryland Extension and an expert on herpetology.
Damage to Plants:
Will cicadas damage flowers or vegetables in my garden?
Cicadas are harmless to most plants. They don’t chew plant leaves, instead they get their nutrients by sucking on xylem sap from woody plants.
Do cicadas cause damage to trees and how do we prevent it?
If many female cicadas lay their eggs in the branches of trees, it may cause tips of branches to wilt and die. Larger, healthier trees will recover with no lasting impact. However young or newly planted trees are at risk of long-term damage or death. You can protect smaller trees by wrapping the tree with mesh. Openings in the netting should be less than 1 cm or about ⅜ inch in width. This will exclude cicadas and keep them away from branches.
Some have expressed concern that netting may entrap birds or other animals. Inspect your trees before applying netting to ensure no birds or other animals become trapped. Secure the netting around the trunk to prevent animals from entering. If you are concerned about netting trees due to potential harm to other animals, you may opt not to net them.
Some have expressed concern that netting may entrap birds or other animals. Inspect your trees before applying netting to ensure no birds or other animals become trapped. Secure the netting around the trunk to prevent animals from entering. If you are concerned about netting trees due to potential harm to other animals, you may opt not to net them.
When should I plant trees this year in my yard?
Many landowners plant trees in spring or fall. Given that the Brood X will be active this year (2021) in May and June, if you live in an area where cicadas appeared in 2004, consider waiting to plant small trees until the fall.
Can I use insecticides to get rid of cicadas?
Using insecticides isn’t recommended for cicadas. Studies show that insecticide applications provide far less protection than netting that excludes cicadas. Moreover, insecticides may harm other beneficial insects or animals in the landscape. Newly planted trees can be protected by wrapping trees in netting with a mesh size of 1 cm or ⅜ of and inch or less.
Do cicadas benefit plants in any way?
After periodical cicadas emerge and adults die off, their bodies decompose and return nutrients into the ground, allowing plants to use those nutrients. Cicada exit holes may also aerate the soil beneath trees which enhances rain water filtration into the soil.
Can I add cicadas to my compost heap?
Yes! Following emergence and mating of periodical cicadas, adults will die and their bodies will decompose, making them a perfect addition to your compost pile.
Do periodical cicadas provide any benefits to us or to the environment?
Due to their numbers, cicadas provide significant nutrient contributions to predators (as prey) and plants (as fertilizer). Researchers have determined that some avian populations can increase following periodical cicada emergence. Other animals may benefit from the cicada bounty.
Human beings also benefit from cicadas! Not only are they amazing for adults and children to learn elements of biology and ecology, they have long been featured in music (Bob Dylan’s “Day of the Locusts”) and have served as inspiration to artists (Van Gogh sketched cicadas!).
Human beings also benefit from cicadas! Not only are they amazing for adults and children to learn elements of biology and ecology, they have long been featured in music (Bob Dylan’s “Day of the Locusts”) and have served as inspiration to artists (Van Gogh sketched cicadas!).
How are cicadas affected by human land development and urbanization?
Since cicadas rely on wooded areas for growth and reproduction, habitat loss due to development and urbanization is a substantial threat.
How can I help periodical cicadas?
You can plant trees, trees and more trees! Also – advocate for and participate in preserving and increasing natural habitats and increasing urban green spaces. Please do not use pesticides to kill cicadas.