As spring turns to summer in the United States, warming conditions have started to summon enormous numbers of red-eyed periodical cicadas out of their holes in the soil across the east of the country. This year sees an exceptionally rare joint emergence of two cicada broods: one that surfaces every 13 years and another with a 17-year cycle. They last emerged together in 1803, when Thomas Jefferson was US president. This year, billions or even trillions of cicadas from these two broods — each including multiple species of the genus Magicicada — are expected to swarm forests, fields and urban neighbourhoods.
To answer readers’ cicada questions, Nature sought help from three researchers. Katie Dana is an entomologist affiliated with the Illinois Natural History Survey at the University of Illinois at Urbana-Champaign. John Lill is an insect ecologist at George Washington University in Washington DC. Fatima Husain is a cognitive neuroscientist at the University of Illinois at Urbana-Champaign. Their answers have been edited for length and clarity.
JL: We’re not really sure. We do know that cicadas’ eyes turn red in the winter before [the insects] come out. The whole coloration pattern in periodical cicadas is very bright: red eyes, black and orange wings. They’re quite different from the annual cicadas, which are green and black, and more camouflaged. It’s a bit of an enigma why the periodical ones are so brightly coloured, given that it just makes them more obvious to predators. There are no associated defences with being brightly coloured — it kind of flies in the face of what we know about bright coloration in a lot of other animals, where usually it’s some kind of signal for toxicity. There also exist mutants with brown, orange, golden or even blue eyes. People hunt for blue-eyed ones; it’s like trying to find a four-leaf clover.
Can periodical cicadas see in colour?
JL: They do see colour. But their eyes are basically non-functional when they’re underground. They’re not investing a lot of energy in making the sort of proteins associated with vision when they’re not needed. And so there’s some dramatic, abrupt developmental switch that happens, that probably coincides with the eye colour changing to red. They now need to be able to use their eyes in a new habitat, which is above ground.
KD: We know that they can interbreed when introduced to each other in the lab, but it remains to be seen if it actually happens in a wild setting.
Do cicadas compete to be heard?
JL: Cicadas get together in all-male groups called choruses, and usually in a given tree. Cicadas of a particular species congregate together, put on a big show, and the females are hanging out around the periphery, judging the quality of potential mates. So that’s the reason it’s so loud, but I don’t know the degree to which they’re competing to be heard. They’re obviously trying to distinguish themselves among an already loud group, for the females. And the females are judging something about the quality of the call. But I think the loudness is probably correlated with how vigorous that male is, and might indicate [for a female] good genes to pass on to her offspring, so that she can, in turn, have loud-calling sons that would pass on those genes.
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Can the incessant din of cicadas cause people to develop conditions such as temporary psychosis?
FH: I highly doubt that the loud noise of the cicadas causes temporary psychosis. At least, I have not heard of any such cases. People do have hypersensitivity to loud sounds and may find the cicada noises bothersome. Some may find that the noise exacerbates their tinnitus. But for some others, the cicada noise can actually mask their tinnitus.
If cicada males buzz to attract females, is it possible that females of one species will be attracted to males of the other species?
KD: Noise absolutely brings female cicadas. If you run a lawnmower these days, all the cicadas will flock to you. But once they get closer to each other, there’s a call-and-response that’s more species-specific. The other thing is that in insects, we often talk about lock and key: the male [reproductive organ] is the key and the female [reproductive organ] is the lock, and they have to fit together perfectly. That’s how a lot of insect species make sure they’re mating with the right species.
Do any insects thrive on periodical feasts of cicadas?
JL: The cicada killer [Sphecius speciosus] is one of the largest native, stinging wasps that we have in this area [the eastern United States]. But the wasps don’t really start foraging until after the periodical cicadas are mostly gone. They mostly feed on the larger, green annual cicadas [family Cicadidae] that come out later in the year. The wasps capture cicadas and paralyse them with their venom and then bring them back to a pre-dug nest in the ground, where they lay an egg upon them. And the cicada serves as live meat for the developing wasp larva that will feed underground on the hapless cicada that gets eaten alive by the wasp larva.
You'll have to thank the male cicadas for all that screeching. Male cicadas synchronize their calls and produce congregational songs, according to Britannica, which establish territory and attract females. There is also a courting call that they make before mating.
But why is it so noisy in the first place? As you may have guessed, it's all about reproduction. Male cicadas create the classic chirp-click to attract a mate. If the female likes what they hear, well then, all of that cacophony ensures that the species will return in good time.
The summer of 2024 is especially full of periodical cicadas because two different broods are emerging together. Between Brood XIX, a group of 13-year cicadas, and Brood XIII, ironically a group of 17-year cicadas, approximately one trillion cicadas will arrive, across 16 states.
If a cicada lands on you, it's by accident. Cicadas fly around looking for hardwood trees or woody shrubs to land on, where they hope to attract a mate and lay their eggs. In places like cities, there are often more people than trees and the cicadas might have to spend some time flying around to find the right spot.
Cicadas do not bite or sting, and they are not poisonous. However, if your pet consumes many cicadas, this could lead to digestive issues. Additionally, cicadas are biologically similar to crustaceans such as shrimp.
However, the periodical cicadas, which emerge every 13 or 17 years, can create noise for 4 to 6 weeks after they emerge in May or early June. Once mating is complete, and eggs are laid, adult cicadas die, and the noise subsides until the next generation emerges years later.
That means many of this year's periodical cicadas are set to die in June, though some could die off in late May or July, depending on when they emerged. The nymphs of annual cicadas remain underground for two to five years, according to the Missouri Department of Conservation.
What makes cicadas stop singing? Most, if not all cicadas sing during the day, but what time of day they sing depends on the species and the weather. There are over 3,000 species of cicadas, and each has its own unique behavior. Typically, cicadas do not sing at night, but there are exceptions.
Here's what experts want you to know. "Insects that utilize trees are strongly attracted to upright dark silhouettes and a human standing on an open area is close enough," added Day. "So cicadas and wood-boring beetles will go right towards any dark upright object."
Cicadas are commonly eaten by birds and mammals, as well as bats, wasps, mantises, spiders, and robber flies. In times of mass emergence of cicadas, various amphibians, fish, reptiles, mammals, and birds change their foraging habits so as to benefit from the glut.
Cicadas are not dangerous and can provide some environmental benefits including: Cicadas are a valuable food source for birds and other predators. Cicadas can aerate lawns and improve water filtration into the ground. Cicadas add nutrients to the soil as they decompose.
The hotter the day, the louder the male cicadas make their sounds. 3. Male cicadas make several types of sounds including a mating call, a distress call, an encounter call (or celebration call) which is made after the female agrees to mate and a call to signal they want to be alone.
For extra protection, while mowing your lawn, you can even wear something like this pop-up mesh pod to protect your face and upper body from contact with those persistent cicadas. This personal bug net keeps out cicadas, mosquitoes, or black flies.
Most individual cicadas live only a few weeks, but since they emerge over a period of two weeks or so the whole event lasts longer. The serious noise will get going about a week and half after you first notice them and will last about two weeks more. After that things get a lot quieter.
Male cicadas have sound boxes in their abdomens. They make their sound by expanding and contracting a membrane called a tymbal. They use their sound to attract females, which make clicking noises when they are ready to mate. The hotter the day, the louder the male cicadas make their sounds.
That loud insect noise at night comes from the cicadas unique type of abdomen, called a tymbal, which acts like a drum—when the cicada vibrates this tymbal (similar to the motion created by pressing on the top of a metal bottle cap), it creates a loud buzzing noise.
When a cicada detects a predator nearby, it sings more quietly or stops altogether in the hope the hunter is attracted to a neighbouring cicada. The cicada belongs to a division of insects called the Neoptera, which includes most of the winged insects.
Introduction: My name is Dr. Pierre Goyette, I am a enchanting, powerful, jolly, rich, graceful, colorful, zany person who loves writing and wants to share my knowledge and understanding with you.
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