Month: May 2021

In a previous episode, we described the bizarre strategy called predator satiation used by periodical cicadas to overwhelm hordes of hungry predators intent on filling their bellies with these nutritious insects. The cicada’s long life span may also enable periodical cicadas to elude short-lived predators such as birds and small mammals that simply track cicadas through time. Who can wait 13 or 17 years for their next meal? But one patient nemesis of periodical cicadas has evolved a diabolical plan for making the most of the cicada bounty. In the soil beneath trees where cicada nymphs spend their youth sipping sap, resting spores of the fungal pathogen Massospora cicadina lay in wait for 13 or 17 years. During April and May as cicada nymphs escape from the earth, spores of Massospora adhere to the exoskeletons of nymphs. Compounds on the surface of the cicada send a signal to the spores that dinner is served and it is time to germinate. Like an invading army, the fungus penetrates the skin of the cicada and multiplies, turning the cicada into a fungus garden. In a short suspense, the infection turns the abdomen of the cicada into a buff-colored mass of fungus. At this stage of their life cycle, tens of thousands of newly molted adult cicadas populate the landscape to begin the courtship rituals. The infection sterilizes both male and female cicadas, but does nothing to quell the libido of the sex-crazed male cicada. Infected males continue to seek and attempt to mate with females despite their contagious infection. In a game of tit for tat, female cicadas infected with Massospora remain attractive to healthy males that soon become infected as they attempt to mate with females. At this point in time Massospora becomes a cicada STD and is transmitted from one cicada to another, thereby increasing its numbers each day. While the STD is strange enough, Massospora has one more trick to ensure maximum transmission of its spores. Recall from last week’s episode, that in the cicada mating game, after the male cicada puts on his best performance, the female signals her willingness to mate with an audible series of wing flicks. By a still not fully understood physiological mechanism, Massospora exerts mind control over an infected male cicada, causing him to mimic the female’s wing flick behavior. This results in horny male cicadas attempting to mate with Massospora infected males, further spreading the fungus through the cicadas’ populations.

Early in the Massospora infection cycle males and females with distended, distorted abdomens appear. Soon, fungal spore masses replace terminal abdominal segments. Sterile infected cicadas walk around and fly about, attempting to mate with uninfected cicadas and spewing spores into the environment while infecting their brood mates. Nearby, a healthy male cicada becomes entangled with an infected cicada in a bizarre pas de deux. In a strange twist of mind control, Massospora causes male cicadas to mimic the female’s wing-flick behavior, her coy signal of willingness to mate. Watch as a male uses his courtship call and attempts to woo a fungus-infected cicada that had just flicked its wings. His overactive libido will likely end in a lethal infection,n further spreading Massospora through cicada land. Videos by Michael Raupp and Paula Shrewsbury

A recent discovery of psychoactive compounds produced by Massospora suggests that these neuromodulators may play a role in altering the male’s behavior, contributing to the active transmission of the fungus by the cicada. Infected cicadas are flight capable and their peregrinations carry the fungus to new habitats as cicadas fly about. In low density populations of cicadas, mortality rates caused by Massospora range < 5% to ~ 25%. A second, more sinister wave of infection follows the first. In this stage, fungus-laden abdomens of infected cicadas and dying infected cicadas inoculate the soil with the resting spores of Massospora. While the loss of an abdomen spells instant death for a human, this is not the case for a cicada. Sensory and integrative neurological functions in the head and locomotory functions of flight and walking directed by the thorax remain intact despite the loss of the abdomen.  As the season of the cicada progresses throughout cicada land, keep an eye out for male and female Massospora victims as they walk about missing their abdomen, macabre reminders of a very clever fungus.

Acknowledgements

The wonderful articles “A specialized fungal parasite (Massospora cicadina) hijacks the sexual signals of periodical cicadas (Hemiptera: Cicadidae: Magicicada) by John R. Cooley, David C. Marshall, and Kathy B. R. Hill, “The ecology, behavior, and evolution of periodical cicadas” by K. S. Williams and C. Simon, and “Behavioral betrayal: How select fungal parasites enlist living insects to do their bidding” by Brian Lovett, Angie Macias, Jason E. Stajich, John Cooley, Jørgen Eilenberg, Henrik H. de Fine Licht, and Matt T. Kasson where used to prepare this episode.

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In last week’s episode, we watched periodical cicadas emerge from the ground after seventeen years, make a mad dash for a tree or other vertical structure, latch on, and shed their juvenile exoskeleton. Many fell to predators or simply failed to escape from their youthful skin and perished without enjoying a moment in the sun. But for the lucky ones surviving the first night of terror, the ghost-like newly molted cicada soon morphed into the spectacular, fully formed cicada bedecked with dazzling vermillion eyes, jet black body, and striking orange wing veins. With haste, survivors made their way to the relative safety of the treetops to complete their transformation into adults. Newly molted cicadas, termed teneral adults, spend the next several days waiting for their exoskeleton to harden before appendages used to insert eggs into branches, or other structures used in flight, sound production, and mating, become fully functional. As this maturation proceeds, cicadas move by foot or wing to treetops and underlying shrubs, vegetation or human-made structures to begin the mating game.

Acoustic signaling, the production of various sounds, is a key element in cicada reproduction. Just behind the thorax on either side on the male cicada’s body, hidden by the wings, is a drumhead-like structure called the tymbal organ. Powerful underlying muscles vibrate the tymbals, creating sound which is further amplified by hollow reverberation chambers within the abdomen of the cicada. While only the male sings, both males and females listen with an ear-like tympanum on the undersurface of their abdomen. Male cicadas have a profound repertoire of sounds. When under attack by a predator, a screechy alarm call issues forth from the cicada’s abdomen. An encounter with the alarm call likely disorients naïve would-be predators or bug geeks handling a cicada for the first time. Creating sound to escape predators is one thing, but the primary function of tymbals and their songs is to ensure the fidelity and perpetuation of the three species of periodical cicadas emerging as Brood X. To successfully reproduce, members of the same species must be in the same place at the same time to find a mate. Using unique and distinctive choruses, male cicadas sing loud and long to attract females and other males of their species to specific locations for the purpose of mate selection. The loudness of the big boy band of hundreds of cicadas singing in concert can range from 80 to more than 100 decibels. These choruses are often in fairly well defined locations such as a single large tree or group of trees. Near my home in Columbia, Maryland, a veteran ash tree has served as the party site for a raucous band of M. cassini for more than a week. Another nearby silver maple trees hosts a mellow chorus of M. septendecim.

A periodical cicada ascends to the treetop to join his brood-mates. Males create sound by vibrating tymbal organs on both sides of their abdomen just beneath their wings. Hundreds of males form load choruses to attract others of their own species. Watch as a pharaoh cicada cruises the chorus using his courtship song to locate an interested female. Nearby, another hopeful male gets the attention of a coy female who flicks her wings several times. Wing flicks accompanied by clicking sounds usually signify a willingness to mate. However, as the suitor closes in to seal the deal, his hopes are dashed when the lady changes her mind and flies away. On a nearby branch another male finds a mate and fulfills his biological imperative.

Once the gals show up to the chorus, it’s all about romance. When cicadas get eyeball to eyeball, the male cicada uses a variety of courtship songs to convince that special someone that she should be the mother of his nymphs. If his performance is good, she will communicate her willingness to mate with choreographed flicks of her wings accompanied by an audible click. Amidst the cacophonous rock concert in the treetops, these teen lovers consummate their interlude with a prolonged bout of mating. Males and females often remain joined for hours during these encounters. Do periodical cicadas really mime Woodstock 1969 every seventeen years? My busy suburban neighborhood lies in the flight path of a major international airport and on warm sunny days lawn mowers and other machines with small engines create a noisome serenade. It has been observed by several folks that cicadas will amp up the volume of their choruses as airplanes soar overhead or lawn mowers create their rackets nearby. A distinguished colleague recently offered that female cicadas likely choose a worthy mate by the loudness of his performance. Apparently, in a strategic competition to find a mate, boisterous, chorusing males are not to be outdone by the noisy contrivances of humans.

Mating cicadas may remain joined for hours. However, when the paparazzi show up and shatter the romance, this shy couple tries to escape the probing lens of the camera.

Acknowledgements

Bug of the Week thanks Dr. Shrewsbury for helping wrangle cicadas for photography and videography.We thank many members of print and non-print media for providing the inspiration for this episode.

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Last week we talked about a trickle, but not a flood of cicadas, here in the DMV. A few days in the mid – 70s with showers here and there changed the situation rather dramatically. In many areas in northern Virginia, Maryland, and DC hordes of cicadas appeared over the past several days. As the vanguard of Brood X arrived in fifteen states ranging from Georgia to New York in the east and states bordering the Mississippi to the west, their strange strategy for survival, predatory satiation, dramatically took center stage in millions of backyards. While annual cicadas depend on stealth and speed to survive, periodical cicadas play a bizarre “safety in numbers” game. By emerging by the billions almost simultaneously, they fill the bellies of every predator that wants to eat them and yet enough survive to perpetuate the three species known as Brood X.

During the next three weeks, billions of cicadas will make a jailbreak after seventeen years underground. The lucky ones will join a tidal wave of other nymphs as they ascend trees and other vertical structures at night. This late riser successfully shed her exoskeleton in the waning hours of night. After ascending the tree at dawn and pausing to expand her wings on the shell of a brood mate, she must wait several days for her body to harden before flying to the treetops to find her mate.

While holding a record for the longest juvenile period of any insect (termite queens live a longer adult life span at more than 50 years), they escape above ground predators for 17 years. However, their interment underground while sucking on plant roots comes with its own perils.  Three ancient oaks in a nearby park spawned thousands of cicadas in 2004. Five years ago, two of these veterans were removed and the root systems subsequently died. Conspicuously absent around the stumps this spring were any signs of cicadas or their exit holes. At the base of the remaining giant, another bumper crop of cicadas has made their appearance. Development also imperils cicadas beneath the earth. Homes, parking lots, driveways, office buildings and other forms of human development supplant trees with impervious surfaces, the death knell for cicadas. On the micro-level, even patios and stepping stones in a garden can prevent these teenagers from enjoying their brief moment in the sun.

Death comes in many forms to Brood X cicadas. Impervious surfaces like garden pavers prevent the nymphs’ escape from the earth. Pathogens kill many nymphs underground prior to emergence. Fierce carpenter ants feast on helpless newly molted adults on the night of their disinterment. Woodpeckers, grackles, mockingbirds, flycatchers, sparrows, and many other birds and small mammals, including foxes and squirrels, devour cicadas by night and day.  Clumsy nymphs ready to molt latch onto their kin, dooming themselves and their brood mates. Watch as one nymph dislodges another, sending it to a certain death on the ground below, a comical yet tragic ending to seventeen years underground and an almost completed life. Images of squirrel and grackle by Dan Gruner; Jack Bush provided the nighttime image of a fox.

The biggest winners in this game of life and death are all the creatures higher up the food web that benefit from the bounty provided by periodical cicadas. For the vanguard of cicadas storming the world above ground, the carnage will be great. Foxes, raccoons, squirrels, and dogs spent the last several weeks unearthing delectable cicada nymphs. Birds and non-feathered reptiles are feasting. Periodical cicadas are a bounty for many species of birds, a banquet resulting in larger clutches of eggs, shorter inter-clutch intervals, higher nestling body mass, and higher fledgling success during this year’s emergence of periodical cicada. In my neighborhood a pair of nesting hawks spends their afternoons swooping down to lawns below to catch cicadas and return them to a nest with some very healthy looking eyas.

Unfortunately, this run of moderately warm days with unusually chilly nights seems to have taken an unusual toll on cicadas. Many nymphs emerging from the earth near dusk with temperatures in the upper 60s, hit a developmental brick wall as temperatures rapidly dropped to the low 50s and 40s during the night. Failure to complete the process of shedding their nymphal skin seems to be accounting for unusually high levels of molting failure and death in these early risers. But for Brood X in the mid-Atlantic, good news may be just around the corner with a forecast of daytime highs in the 80s and nighttime lows in the 60s. Get ready for teenagers rockin’ in the treetops by this time next week.    

Acknowledgements

Bug of the Week thanks Randy for allowing us to visit her cicada sanctuary and Dan Gruner and Jack Bush for providing images. Two great references “Reproductive responses of sparrows to a superabundant food supply” by T. R. Anderson, and “Effects of superabundant food on breeding success and behavior of the red-winged blackbird” by C. E. Strehl and J. White were used to prepare this episode.

To keep current on what’s up with the 2021 Brood X cicada emergence in the DMV, check in with the Cicada Crew at the University of Maryland.

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In last week’s episode, we heard about the arrival of Brood X periodical cicadas in the deep South, Georgia, North Carolina, and Tennessee, where cicada adults are up and out of the ground and ushering in the main event in this region. This week we also viewed some great video of emerging cicada nymphs in northern Virginia near Tysons Corner. As an alum and emeritus of the University of Maryland, I was particularly intrigued by a reported sighting of periodical cicadas made by several Terp students on April 27th near our iconic Memorial Chapel. On the eve of Tuesday May 4, following a day of near record temperatures in the 80s punctuated by rain showers, a cicada safari seemed in order. High temperatures and the high relative humidity that follows a late afternoon storm are often the perfect conditions to trigger emergence of cicadas. After searching dozens of stately oaks near the chapel, around 10 pm I was rewarded with the discovery of cicada nymphs rising from their subterranean crypts after 17 years, and ascending a nearby willow oak. Not exactly the flood I was hoping for, but the gentle trickle of cicadas provided a pleasant ending to the safari. This week has seen a deluge of journalists and cicada enthusiasts hoping to witness the upcoming cicada tsunami in the DMV but, alas, Mother Nature is teasing us. With daily high temperatures forecast to be in the 60’s and several cloudy and showery days scheduled for the upcoming week, it looks like the massive emergence here in the DMV – the cicadapalooza – will be delayed just a bit. As my meteorologist friends assure me, this could all turn around quickly with a blast of warm, humid air from the south. Let’s keep our fingers crossed.

Cicada safaris often begin at dusk and stretch into the dead of night. At the base of a veteran oak tree, shed skins of cicadas provide a clue that the big jailbreak is near. As weather warms over the next several weeks, a cicada trickle becomes a cicada tsunami.

Another curious event happened this week while visiting a few cicada nymphs beneath the earth with a film crew from the BBC. The question arose about gender identity of cicadas, and was it possible to tell the guys from the gals. As with many sexually reproducing organisms on earth, the equipment for mating is fundamentally different between males and females. After unearthing several fifth instar Magicicada nymphs and examining their rear ends, it was easy to resolve this query. The male nymph bears a singular slightly enlarged bump at the tip of his abdomen, that when fully developed in the adult stage will be his intromittent organ, called an aedeagus. The nymphs destined to be a female have two darker triangularly shaped structures at the tip of their abdomen that will house the ovipositor of the female. The ovipositor is the appendage used to slit pencil sized branches and insert eggs into egg nests.  Images of the abdomens of males and females are provided here to help clarify the difference between the sexes. For adult cicadas, it is easier to tell the guys from the gals.

When warm weather returns, be on the lookout for adult cicadas and be sure to use the appropriate gender designation for the males and females when you greet them.

Acknowledgements

Bug of the Week thanks Billy, Stephen, and Mike and the BBC for providing inspiration for this episode. Thanks also to Richard Scott Rupert and the entire crew of the Arboretum, Botanical Gardens, and Landscape Services at the University of Maryland. Thanks also to Colette, Virginia, and Trinadee who discovered the magical oak that spawned these early rising cicadas at the University of Maryland.   

To keep current on what’s up with the 2021 Brood X cicada emergence in the DMV, check in with the Cicada Crew at the University of Maryland.

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Recent episodes of Bug of the Week explored elements of cicada biology and several frequently asked questions about the soon-to-erupt volcano of Brood X periodical cicadas. We dispelled the notion that cicadas were locusts, put to rest the idea that they hibernated for 17 years underground, explained what was up with all those holes in the ground, and provided an educated guess as to when they might be seen in our region. Save for a lone outlier that showed up early just outside of Towson on April 19th and another that emerged in Rockville a few days later, adult cicadas remained scarce not only in our area, but around the nation. Last week all of this changed with scores of adult cicadas coming out of the ground in Tennessee and North Carolina. Closer to home several eagle-eyed students witnessed emerging cicadas ascending one of the stately ancient oak trees on the College Park campus of the University of Maryland as night fell on April 27th.  With air temperatures in the 70s and 80s this week, rain expected, and soil temperatures bouncing around the mid-60s, conditions seem right for the massive jailbreak to begin in some locations in our region. For several other broods Bug of the Week has visited, a warm day with an afternoon thunderstorm seems to create favorable conditions to trigger an emergence. Perhaps the higher relative humidity that follows a rain facilitates the Houdini-like escape of the cicada from its nymphal skin and reduces the chance of an early death.

On the night of April 27th, 2021, students in an ecology course recorded periodical cicadas emerging from the soil and scaling an ancient oak tree on the campus of the University of Maryland, College Park. Due to its rich tree canopy and long history of Brood X cicada appearances, tens of thousands of periodical cicadas will emerge on campus over the next several weeks. Video credit: Colette Lord

Over the past weeks, several attendees viewing virtual presentations about cicadas wanted to hear the legend of blue-eyed cicadas. Are there blue-eyed cicadas and, more importantly, is there a reward if you find one? The answers are yes and yes. Eye color in insects is a somewhat complicated phenomenon and dependent on which species of insect you are talking about. One of the most well-known examples of eye coloration comes from your old freshman biology buddy, the fruit fly. Noble Prize Winner T. H. Morgan used his discovery of a white eyed mutant of the normally red eyed fruit fly, Drosophila melanogaster, to describe patterns of inheritance and create the first genetic maps. While beneath the earth as nymphs, periodical cicadas have white eyes devoid of pigments. During the year of emergence, eye color changes to a deep vermillion, a color similar in shade to that seen in many species of flies. The red color of fly eyes is created by a group of ommochrome and pteridine pigments known as screening pigments. These pigments filter white light and enable red wavelengths to assist the normal function of rhodopsin, a photosensitive pigment found in the eye of the fly. Mutations affecting the formation of pigments alter eye color in these and other flies. Is the same true for cicadas?  While failing to find a specific reference on the physiological mechanism governing eye color in cicadas, observing variation in cicada eye color is never a problem, if you observe enough cicadas. I see variation in color within every brood. The most common color is a deep red hue, but sometimes shades of orange, white, or beautiful pale blue are seen.

And what about the reward for finding a blue eyed cicada? Well, the reward is simply that you found one. As cicadas emerge, please take the time to look many in the eye and claim your reward. Happy hunting!

Acknowledgements

Bug of the Week thanks Colette, Virginia and Trinadee for their brilliant observations of periodical cicadas on our campus this week. Special thanks to Colette and Virginia for sharing their images and videos and to Dr. Dan Gruner for putting his ecology students on cicada reconnaissance missions. The interesting article “Colour in the eyes of insects” by D.G. Stavenga was consulted for this episode. 

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