What are cicadas? Cicadas are members of the superfamily Cicadoidea and are physically distinguished by their stout bodies, broad heads, clear-membraned wings, and large compound eyes.
There are more than 3,000 species of cicadas, which fall into roughly two categories: annual cicadas, which are spotted every year, and periodical cicadas, which spend most of their lives underground and only emerge once every decade or two.
Cicadas are famous for their penchant for disappearing entirely for many years, only to reappear in force at a regular interval. Despite their name, annual cicadas generally live for two to five years—though some species may live longer—and their brood life cycles overlap, meaning that every summer, some cicadas emerge. Even periodical cicadas occur most years in different geographic regions as they are split among 15 brood cycles, each lasting 13 or 17 years.
The cicadas’ amazing lifestyle has been a source of fascination since ancient times. Several cultures regarded these insects as powerful symbols of rebirth due to their unusual life cycles. In early Chinese folklore, cicadas were also considered high-status creatures that rulers should seek to emulate in their purity, and cicada motifs even became incorporated into imperial court wardrobes in the seventh century.
Geographic range While annual cicadas can be found throughout the world, periodicals are unique to North America. Periodical broods are concentrated in the central and eastern regions of the United States, and some areas are home to multiple broods.
Life cycle The cicada life cycle has three stages: eggs, nymphs, and adults. Female cicadas can lay up to 400 eggs divided among dozens of sites—generally in twigs and branches. After six to 10 weeks, young cicada nymphs hatch from their eggs and dig themselves into the ground to suck the liquids of plant roots. They spend their entire developmental period in these underground burrows before molting their shells and surfacing as adults to mate and lay eggs.
The developmental process varies in length, but periodical broods emerge in synchrony depending on the year and soil temperature. They wait for the right conditions for breeding, which are when the ground thaws to 65°F (18°C) in a brood’s designated year. It’s not clear why these cicadas have such distinct and oddly timed cycles, though some scientists theorize it has to do with avoiding predators.
Periodical cicadas do not create destructive plagues, as some locusts do, though as many as 1.5 million cicadas may crowd into a single acre. Unlike locusts, cicadas don’t eat vegetation but rather drink the sap from tree roots, twigs, and branches. Large swarms can overwhelm and damage young trees by feeding and laying eggs in them, but older trees usually escape without serious damage as cicadas don’t stick around for long. Adults die off within about four to six weeks after emerging.
Vocalizations Cicadas are also known for their buzzing and clicking noises, which can be amplified by multitudes of insects into an overpowering hum. Males produce this species-specific noise with vibrating membranes on their abdomens. The sounds vary widely, and some species are more musical than others. Though cicada noises may sound alike to humans, the insects use different calls to express alarm or attract mates.
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The high-pitched song is actually a mating call belted out by males. Each species has its own distinctive song that only attracts females of its own kind. This allows several different species to coexist. Cicadas are the only insects capable of producing such a unique and loud sound.
“The sound organ in cicadas are tymbals, drum-like structures on the abdomen of the insect. In most species only males have these organs. They are used to “call” females or warn of nearby predators. Females can make sounds but they “flick” their wings to answer the mating calls.”
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Contracting a disease is nobody’s idea of fun, especially when the disease is of the sexually transmitted variety. As far as humans go, most sexually transmitted diseases can be cured with modern medicine, with the exception of HIV/AIDS, herpes and a few others. As it turns out, humans are far from being the only animals that can fall victim to sexually transmitted diseases, as a sizable amount of cicadas die from a brutal form of fungal disease known as Massospora cicadina.
The existence of Massospora cicadina has been known to scientists for quite some time. In fact, the first documented case of the fungal disease in cicadas was published all the way back in 1879. Now, 140 years later, experts have discovered why this fungal disease, which affects cicadas only, spread so rapidly among their populations.
Massospora cicadina is spread in two ways. The first involves infection during the larval stage. Before cicadas reach adulthood, they spend seventeen years maturing beneath the ground. Some of these larval specimens come into contact with a type of fungus that begins growing on their exoskeletons. Shortly before a compromised larva emerges from the ground’s surface, its changing body chemistry releases compounds that prompt the fungus into infecting its host. In this scenario, a cicada becomes infected shortly before emerging from the ground, which makes their seventeen year long larval stage a waste of time. However, researchers now know that the disease can spread further through sexual activity.
Infected male cicadas that emerge from the larval stage begin acting strangely due to the infection spreading to the brain. This strange behavior among males includes flicking their wings like a female. This wing flicking attracts other males that then try to mate with the infected cicada; instead they become infected too. These infected males then go on to mate with females. These females then mate with more males that are disease-free. Given the rate of sexual activity that occurs during a cicada’s short adult life, the disease spreads rapidly. Between two to five percent of the total cicada population is infected with this disease, and this estimate does not include cicadas that became infected through sexual activity.
Have you ever heard of any other types of sexually transmitted diseases that are spread among insects?
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One of the (many) cicada poems from our local paper:
Seventeen years I sheltered in place, safely masked by my own carapace. Word arrived: The restrictions were over. I emerged to the sunlight and clover.
My purpose in life was to mate me. I sang for a female to date me. My song made the neighborhood hate me, and then came a squirrel - and ate me.
The only thing needed for the triumph of evil is that good men do nothing - Edmund Burke