CICADA LIFE CYCLE
What triggers cicada nymphs to emerge from the ground is still unknown. With Magicicadas, it's been well plotted over the past 200 years where and when they'll exactly emerge. 13 year Magicicadas emerging in the Southern states will start their emergence in late April to early May while the Northern 17 year species will begin to emerge in late May and early June. Okanagana will also begin to emerge in June while their larger cousins the "Dog Days" won't begin until late June to mid-July. Neotibicen emergence sometimes will last until early September.
Whatever the reason, weeks before emergence, the mature nymph will begin to tunnel toward the surface of the ground. The nymphs will make a chamber just below the surface that will be water proof with tunnel walls will be completely compacted and smooth. With Magicicadas, they may even construct a hut or "chimney" that can extend one to two inches above the surface. The Magicicada nymphs will construct these chimneys in order to elude ground moisture. At this stage in life, one can see the evidence of an adult cicada ready to be born. With Magicicadas, you can see the bright red eyes and well developed wing flaps on the sides of their bodies. Neotibicen nymphs have dark eyes with greenish wing flaps.
EMERGENCE and ECDYSIS:
With Magicicadas, when the soil temperature reaches approximately 64 degrees Fahrenheit at a depth of about 8 inches, they begin to emerge in a mass exodus. Thousands will emerge all at once, usually beginning during the late evening hours that will last until late morning the following day. Very few will emerge during the height of the day since they are more likely to be eaten. Magicicadas can number as many as 20,000 to 40,000 to a tree and up to 1.5 million an acre. Nymphs will leave behind emergence holes on the soil surface thus making it resemble Swiss cheese. During these large emergences, nymphs crawling through the leaf litter of the forest canopy will resemble the sounds of a rain shower. Neotibicens emerge in far fewer numbers and it is rare to find a tree with over a hundred. Neotibicens usually are two or three per tree. Sometimes, trees can number up to 50 or 60.
Once issued from the ground, the nymphs will slowly walk around in search of a sturdy support which will assist them in "molting" or casting off their final skin. Tree trunks, branches, flower stems, leaves, tall blades of grass, fence posts, and roadway signs are often used. Nymphs will even climb animals and a person's leg if they'll hold still long enough.
Once a support is selected, the nymphs will climb anywhere from an inch to over thirty feet off of the ground until they fasten themselves in a secure position. The skin will slowly split down the back and an imago or "adult" cicada will eventually remove its head first through muscle contractions. This process is called "ecdysis." Cicadas have soft white frail bodies or a "teneral" stage that will take several hours to harden and darken. Neotibicens will be ready to actually fly within a few hours. Magicicadas won't be strong flyers for a few days. Many cicadas have false "eye spots" on their backs just behind their head that can deter predators. The cicada slowly removes itself and may dangle upside down by leaning backyard. Their wings slowly unfold and expand until they extend past their abdomens. These insects look very beautiful at this stage. The cicada will eventually sit up and clutch their old shell or "exuvia" and right themselves. These exuviae which are sometimes referred to as "ghosts," can remain on the tree trunks for many months after the adult has died off. I recall a Neotibicen exuvia hanging on a branch as late as early July the following year.
Cicadas emerging in large numbers will often overcrowd themselves and compete for available space. The nymphs will tumble and climb over one another and can knock their brothers and sisters off the side of the tree. Cicadas that have freshly emerged and are knocked down from a considerable height will often parish from the fall. Some will be become crippled or their wings will no longer fully expand. Cicadas will molt or "eclose" on top of other cicadas who are also trying to remove themselves from their nymphal skins. These cicadas may become trapped in their skins and parish. Either from temperature fluctuation or inadequate moisture levels, some cicadas do not successfully eclose and become trapped and/or only partially emerged from their shells. These cicadas will eventually die, either baked by the sun or eaten by scavengers. During a dense Magicicada emergence, it is not uncommon to find piles of exuviae or dead adults lying at the base of a tree. Adult cicadas with deformed or shriveled wings are also found near the bottom or bases of these trees and are more susceptible to predation. Some of these adults, now in their final "imago," stage, still manage to lead successful lives.
Magicicada emergences will occur over a couple of weeks. With each night, new nymphs will emerge from the ground and begin their ascent into the trees. These newer nymphs will often knock off the older exuviae or trapped adults to make room for the latest round of eclosure. The heaviest of the emergence usually occurs over just a few nights and is a fascinating sight to see!
SINGING and COPULATION:
Several days after emergence, male cicadas will begin to sing in order to attract a mate. Male cicadas produce their loud song with the assistance of vibrating membranes called "tymbals." These organs are located on the underside of their hollow abdomens just behind their hind legs. If you carefully open a male's wings, you'll see that these membranes resemble an ear drum. Only male cicadas have these membranes and produce sound (in most species). Female cicadas remain quiet throughout their lives.
The sound the male cicada produces is the loudest in the insect world and can sometimes be heard up to a 1/4 mile away. Singing usually commences during the early morning hours and will continue throughout the day until dusk. Different species prefer to sing at different times of the day. Listen carefully and you'll be able to tell the difference in their songs. The song of M. (tre) septendecim gives off a loud "Pharaoh" or "Phar-aoh" type call. M. (tre) cassini's song is a series of clicks followed by a loud "zip" sound; while M. (tre) decula sounds like a lawn sprinkler. The common Neotibicen vary between a continuous buzzing, rattling, or sounds similar to a circular saw (N. canicularis). Cicadas stop singing once it becomes dark and it is believed light is what triggers the cicadas to begin singing again. Only once did I ever hear a Neotibicen singing around 5 am (0500 hours) in complete darkness prior to sunrise. The male gave off a few calls and became silent again.
Male cicadas, especially Magicicadas, can gather and produce mass singing aggregations called "chorusing centers." During a large emergence, Magicicadas gather and produce a sound so loud that it's nearly impossible to carry on a conversation, let alone think. The chorus makes it hard for an animal, such as a bird, to pinpoint an exact location since the sound carries. The loudness of the chorus may also deter predators that are simply unfamiliar to the sound since Magicicadas remain unseen for many years. Neotibicens are more solitary than their smaller Magicicada cousins. A Neotibicen is actually louder than a Magicicada if measured by individual insect. But due to a Magicicada's abundance, it's their combined chorus that makes their calls deafening.
Large aggregations of singing males actually assist the Magicicada in mate selection. A female Magicicada is drawn to the sound and will actually select the larger dominate male of the group. This is also common among most species in nature. Females will flick their wings in response to his calls indicating their interest. Once a male is selected, the male will produce a different mating sound which reminds me of someone getting excited! The two of them will conjoin at the abdomen and remain connected for several hours. When the female is so-called "sexually satisfied," she will begin a tug of war with the male in order to free herself. I've observed the male get the worst end of this (no pun intended) and are often dragged about and around until they are separated again. This tug of war often causes the mating pair to drop from the trees where they are easily stepped on or eaten by predators. It is believed female Magicicadas will mate only once and receive a vaginal"plug" from her suitor that will prevent her from mating again. The male is considered a "play boy" and will mate several more times.
MORTALITY & PREDATOR SATIATION:
Each species has their own way of dealing with predators. Neotibicens are very alert and will fly off quickly when approached with danger. Magicicadas have a different approach. Due to their extreme abundance, Magicicadas suffer from what zoologists call "predator foolhardiness." This means Magicicadas will look danger in the face and will make little or no attempt to avert it. Hence, many will be eaten and/or destroyed.
When Magicicadas begin their emergence, predators such as flocks of birds, will gorge themselves and simply become too full to eat any more. During emergence years, predators actually flourish better than on off years. As the Magicicadas continue to emerge in larger numbers, the predator attacks decrease. Hence by the second or third week when Magicicadas begin to procreate, they can do so without being disturbed. This is called "predator satiation." But as the Magicicada numbers begin to decline in late June and early July, predators once again become a factor in eliminating the remaining few.
Magicicadas normally live only a few weeks. They appear in the middle of May (Mid-April for more Southern Broods) and will be gone by mid-July, in time for a second round of annual cicadas. Once Magicicadas begin dying off, their decaying bodies litter the ground and accumulate in dense piles that bake in the hot summer sun. These sun baked bodies will give off a foul odor that can be easily recognized several yards away. Neotibicens also live for but a few weeks with time enough to sing, mate and lay their eggs. Female cicadas die shortly upon completion of their egg laying. I've located female Magicicadas that have expired but still have their ovipositors lodged in the wood of a twig. Once they die, cicadas will drop to the earth where their bodies will be dismembered by ants and other scavengers.
Aside from eluding predators, Magicicadas also suffer from a fungal infection called "Massosporan cicadina." (Massosporan levispora for the Okanagana rimosa species) This fungus lays dormant on the surface of the ground for 13 or 17 years and will affect the emerging cicadas that come forth during their brood years. This fungus attacks the Magicicadas exclusively and will grow inside the cicada's abdomen until the abdomen breaks open and simply falls off. Once the abdomen is dismembered, the fungus spores will be released back onto the ground where it will affect the offspring of the next Magicicada generation many years down the road. This fungus renders the cicada incapable of reproducing and will eventually kill it. However, cicadas infected with the fungus will continue to attempt mating with other cicadas which causes the infection to spread throughout the cicada population. The fungus has little effect on the overall numbers of the cicada population.
Also aside from birds and fungal infections, another chief cicada predator is the female Cicada Killer Wasp (Specius speciosus). The wasp hunts cicadas primarily by sight and sound. This wasp begins to appear in July and targets Neotibicens, since by the time the wasps arrive; most Magicicadas will already be gone. Once the wasp locates a cicada, she tackles it and stings it. The sting merely paralyzes the cicada and renders it helpless. The sting also acts as a preserving agent and will keep the cicada's body from dying and drying out. Stung cicadas will live longer than un-stung cicadas. The wasp will then drag the heavy cicada up the side of a tree and take a short flight with the cicada tucked underneath the wasp's body. The weight of the cicada causes the wasp to fly only a short distance at a time and she will have to repeat this step over and over until she reaches her burrow. The burrow is often located and dug out of loose soil and will extend underground at a depth of a foot or more. This burrow will have several rounded chambers branching off of the main entrance tunnel. There the wasp will store the cicada and lay an egg near the thorax of the cicada's body. The wasp will already know the sex of the egg and will stock two cicadas to a chamber if the egg is female and one cicada if the egg is male. Once the wasp finishes stocking all of the chambers, she will seal off the entrance to the nest. Within several days, the egg will hatch and the wasp larva will begin to feed off the juices from the cicada's body. The cicada will live through much of this ordeal and will be drained by the larva until only a husk remains. The larva will then spin a thin cocoon around itself where it will remain in the larval stage and over winter. In spring, the larva will pupate and emerge from its cocoon during mid-summer. These new wasps will leave their old nests, mate, and the females will dig new burrows to begin the next generation.
Another main factor in controlling cicada populations is severe weather conditions. Heavy rains and strong winds will often dislodge the cicadas from the trees where the cicadas will drop to the ground and drown. Magicicadas will tumble and climb over one another to escape the flooding rain water. It is believed that approximately 40 percent of all cicada populations will perish from predator attacks, another 40 percent will die from thunderstorms and bad weather, while the remaining 20 percent will survive and insure the survival of the next generation.
Cicadas actually have no real method of self-defense. They are herbivores that are often easily picked off by hungry predators. Male cicadas can give off an alarm call or loud "squawk" when attacked by a predator. This sound is very powerful and in combination of the intense vibration from the cicada's body, the predator may be startled and drop it. As stated earlier, cicada songs are carried over a great distance and when done in conjunction with other singing males, will often confuse a predator and make it near impossible for them to locate the insect. When sound levels increase to an alarming rate, as in Magicicadas, the sound can often frighten predators unfamiliar to it. Magicicadas will sometimes drop to the ground when trying to avoid the approach of many predators. On the other hand, Neotibicens are very swift to take flight but can be clumsy flyers.
Cicadas have no stingers, chemical weapons, or odors that will deter predators. In the case of Neotibicens, they are distinctively colored to match that of their surroundings such as the leaves and tree bark. Cicadas have a long beak called a "rostrum" tucked between their forelegs used for piercing twigs to draw nourishment and to retain moisture. People have reported to have been allegedly "stung" by the cicada. In all of the years I've handled cicadas, I can recall twice where a cicada tried to insert its beak into my finger after mistaking it for a twig. The beak reminded me of a pin prick and I felt no real pain. Once the cicada realized its mistake, it quickly withdrew and didn't make a second attempt. The so-called cicada "bite" left no mark or swelling.
ADULT FEEDING HABITS:
It was once believed adult cicadas didn't feed at all. From my observations during the several hot weeks of late June, I've seen many adult Magicicadas clinging in groups to the side of several small trees where they were feeding on the xylem or "sap." They resembled dogs knelt over a water dish since they had their rostrums or "beak-like" mouthparts buried deep into the wood. Occasionally, these same adults would excrete waste called "honeydew" from the pours of their abdomens that resembled small rain drops falling to the ground. When large groups of cicadas feed together in a tree canopy, they can create an "artificial rain" shower.
I've also seen ants scurrying around the feeding cicadas by trying to snatch a quick drink from the hole in the wood the cicadas had created. If an ant began to irritate a feeding cicada, the cicada would merely swat at the ant with its forelegs or flick its wings in protest. This usually deters the ants to go bother some other individual. I've also observed small wasps and flies trying to agitate feeding cicadas with enough persistence that the cicada eventually abandoned its drinking hole and flew away.
EGGS & OVIPOSITING:
Magicicadas begin ovipositing a couple of weeks after emergence, usually early June, and continue doing so into mid-July... Neotibicens also begin laying eggs a couple of weeks after emergence. They usually start near the end of July and will continue, depending on the conditions, into as late as early October. Cicadas will deposit between 300 to 600 eggs. Eggs are often laid in live branches where the eggs swell and collect nutrients from the plant's living tissue. Some cicada species lay their eggs in dead branches. The eggs are laid in pockets in the wood with as many as 30 per pocket or as few as 5.
If the ovipositing female is disturbed by another cicada, she merely swats at them by using her forelegs. This is often enough to give the intruding cicada a subtle hint. The trespassing cicada will either walk or fly away to another branch. If the female cicada isn't disturbed, she will lay a dozen or more pockets in a single branch which is carved out each time by the female cicada's ovipositor. The selected branches are about the thickness of a pencil.
The female will thrust her ovipositor into the wood, causing it to splinter and scar. This process will often kill the branch and is actually a natural pruning process which helps to eliminate the weaker limbs. During heavy Magicicada emergences, the damage done by ovipositing is very apparent and many trees will have withered leaves from top to bottom. Many saplings and younger trees and bushes are often used and sometimes die from this mass egg laying process. This drooping vegetation is commonly referred to as "flagging." For this reason, cicadas are considered serious pests to ornamental trees.
Magicicadas prefer deciduous type forest trees such as ash, oak, hickory, maple, elm, birch, apple, peach, pear, dogwood, walnut, hawthorn, sycamore and many other species of trees and/or plants. I've even seen small thorn bushes used as hosts. Magicicadas will oviposit in pine but they aren't a favorite host. The Magicicada hatch rate is significantly reduced when oviposited in pine trees due to the tree's sickly resin. However, some Neotibicens species prefer pine trees and will use many other types of trees too. Magicicadas prefer forest edges and clearings that are well maintained as opposed to the thick forest canopy.
Cicada eggs are very vulnerable to predators such as mites and certain species of parasitic flies which lay their eggs near that of the cicadas.' The fly eggs hatch before the cicada's and the fly larvae will then make a meal of the cicada's family. Sometimes, eggs are also trapped inside their nest pockets if the tree heals over its wounds at the nest opening.
If all goes well, the eggs will hatch between six and eight weeks. After about two weeks, the red eye spots can be seen in Magicicada eggs. With Neotibicens, their eggs will sometimes over winter. The young cicadas called "nymphs" hatch out of their egg casing which has become soft like a skin membrane. Nymphs are covered in this protective covering that keeps their legs and antennae pressed against their frail bodies. The nymphs wiggle toward the opening of their egg pocket where they dangle at the entrance, held securely by their embryonic skin. The nymphs then discard this skin and scurry about the branch.
The nymphs are blind, and ant-like in appearance, with small hairs on their bodies. The "fossorial" forelegs of the nymphs are enlarged and designed for digging and grasping dirt. They are approximately one sixteenth of an inch in length and are lighter than air. Usually the first gentle breeze will dislodge them and cause them to fall gently to the ground.
Once on the ground, the nymphs again must scurry about until they come across the first crevice or other opening. They will then descend into the dark depths of the earth and remain there for the next two to twenty years, depending upon the species. The nymphs must hurry since they are very vulnerable to predation by ants, spiders, and other enemies. Also, the hot sun will eventually kill them if they fail to make haste.
Once the nymphs begin their descent into the soil, they will often feed on the root fluids of grasses for the first year. Afterward, they will dig deeper into the earth to a depth between two to eighteen inches in search of a suitable tree root to draw their nourishment. Nymphs have also been found at depths greater than two feet. Once a rootlet has been found, nymphs will construct a cell using their own excrement whose walls will be water proof and protect them from drowning during heavy rains and flooding conditions. Species as Magicicada cassini thrive in areas of flood plains. Portions of the land of which they dwell can be submerged under water for long periods of time.
The nymphs grow very slowly and will be safe from most enemies. Even underground, moles, beetle larvae, ants, and other ground dwelling predators can encounter the nymphs and will devour many of them. Nymphs also suffer mortality from failing to locate suitable host rootlets or from parasitic fungi. Very little is known about the nymph's underground life for it is very hard to study.
It is believed that nymphs go through five stages or "instars" during their underground development. Upon completion of each instar stage, the nymphs will "molt" or shed their old skin in order to grow larger. Their cells will also be enlarged to accommodate their growth and sometimes they will relocate to find a larger root. In the case of Magicicadas, the first molt is believed to occur after the first year and will reach nymphal maturity usually between nine to twelve years. From there, they will remain dormant until their 13th or 17th year when some unknown phenomenon will summon them from the earth. Not all nymphs mature at the same rate and some will take shorter or longer to reach nymphal maturity. In overcrowded conditions, nymphs may actually mature slower due to inadequate food sources from competition. This can even expand their development time beyond 17 years. Nymphs that emerge too early or too late from the rest of their Brood are known as "stragglers." Sometimes "straggling" can be 1 to 4 years early or 1 or more years late. During the long winter months, the nymphs will be dormant and survive many months without food. Nymphs will emerge from the ground even after their host tree has been long since cut down.
Thus is the life of a cicada. For most of their lives, they live below the surface in the desolate corridors they make for themselves. Alone in the darkness and in complete isolation they call their home. After the years go by, they will eventually be summoned to the light to live amongst the trees, just to take flight for a few short weeks. Their lives are full of dangers but their time will be of an essence to finish what the generation before had started... For they are destined to sing, reproduce, and finish the path nature has intended for them. Death then comes but their offspring will start the cycle anew. I regress; this is the life of a cicada....
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