Month: April 2021

Before we hail the arrival of the first Brood X cicadas to emerge in Maryland, let’s answer a few frequently asked questions that have popped up repeatedly over the last few weeks. Several viewers and journalists have asked what periodical cicadas have been doing underground for the last seventeen years. Often this query is linked to a related ask about cicadas hibernating for seventeen years. Actually, periodical cicadas have been busy feeding and growing, albeit at a relatively slow pace, ever since they entered the ground in 2004. Yes, in a somewhat COVID-like existence, they have social distanced in subterranean chambers, not to halt the spread of disease, but likely to avoid competing with other cicadas feeding on tree roots. Although they are not the longest lived insect (some termite queens may live over 50 years), at 13 or 17 years as youngsters, periodical cicadas are purported to have the longest juvenile period of any insect.

Adding one more mystery to this magical creature is its strange pattern of youthful development. Immature cicadas are rightly known as nymphs rather than larvae. Larvae are the immature growth stages of insects with complete metamorphosis that have a pupal stage, like beetles, butterflies, bees and several other taxa. Cicadas have incomplete metamorphosis and skip the pupal stage, instead going through several nymphal stages. After hatching from an egg inserted into a tree branch by its mother, a tiny hatchling cicada known as the first instar nymph tumbles to earth and quickly dives underground. In the soil it locates a small root and taps into a vascular tissue, called xylem, where the nymph acquires nutrients and water by imbibing xylem fluids. Clever studies of cicada life underground by Chris Maier revealed surprising development patterns of periodical cicadas. This first nymphal stage of a 17-year cicada usually lasts only a year before it sheds its skin (a.k.a. exoskeleton) and graduates to the second instar nymph. However, after the first year, life in the remaining four stages of a nymph may vary dramatically. Dr. Maier discovered that second instar nymphs were found over a period of six years, third instar nymphs were distributed over eight years, fourth instar nymphs were found over ten years, and fifth and final instar nymphs were found over a seven-year period. Here is the amazing part, despite the apparent disparate and asynchronous rates of development, all of these youngsters managed to emerge from the earth in synchrony in year 17, right on schedule. This mystery is yet unsolved. What about 13 year cicadas? Well, they also scramble across the years at varying rates of development, only faster than the 17-year crew, and they too manage to emerge in synchrony.

In 2004, tiny cicada nymphs the size of a rice grain tumbled to earth, buried themselves, and began feeding on roots of plants. After shedding their skin a few times, they were the size of a jellybean several years later. By year fourteen they had grown to almost one inch in length.  Now cicadas are peeking out of the soil and putting the finishing touches on exit holes before they emerge. Soon the jailbreak will be underway as they dash to vertical structures to shed their skins and head to the treetops.

In a world underground, devoid of light and visual cues, how do periodical cicadas keep track of the years? One hypothesis has it that the annual fluxes of xylem fluids and compounds contained therein may allow cicadas to track the passing of years. In winter when deciduous trees have no leaves, a dramatic reduction in liquids flowing in xylem tissue takes place. In spring when leaves burst forth and transpiration draws water from the roots to leaves in the photosynthetic canopy, xylem pressure changes again. Perhaps, these fluxes are the annual cues to which cicadas “listen.” Another hypothesis not entirely independent from the aforementioned is that a yet unknown molecular clock ticks away the years somewhere within the tiny mind of the cicada in much the same way some dastardly circadian rhythm wakes me at 5:30 am irrespective of when my alarm is set. In addition to the long-term synchronization mentioned above, there is a short-term synchrony, a biological starter’s pistol that signals it is time to make a jailbreak from the earth in year 13 or 17. When soil temperatures reach a temperature of about 64 degrees Fahrenheit, it marks the time in spring when the world above ground is warm enough for cicadas to make a mad dash for a vertical structure, shed their juvenile skins, become adults, ascend trees, best fierce predators, fly to the treetops, make a wonderful, raucous chorus to woo their mates, and for the males, find that special someone willing to be the mother of his nymphs.

This week the vanguard of periodical cicadas appeared in Towson and Rockville, Maryland. The sighting of a periodical cicada in Towson on April 19, 2021 falls within a day of a similar sighting of another periodical cicada near Towson in 2020. A second sighting occurred in Rockville on April 23 of a cicada that emerged in a home from some potting soil that had been brought inside two days earlier. No doubt a couple days of cozy temps inside probably sped up its development, but these two sightings confirm that the cicadapalooza is just around the corner. Cicada-philes, before you get too excited, please look at the graph that accompanies this episode. Here in the DMV the great cicada tsunami is most likely to arrive from the middle to the end of May. With temperatures expected in the 70s and 80s this week, don’t be surprised if a few more early risers appear.  Keep your eyes open.

Acknowledgements

Bug of the Week thanks Jennifer and Tano Arrogancia, Gene Kritsky, and the Cicada Safari for sharing images of Brood X cicadas and providing the inspiration for this episode. The following references where used to prepare this story: “The ecology, behavior, and evolution of periodical cicadas” by K. S. Williams and C. Simon, “Thermal synchronization of emergence in periodical “17-year” cicadas (Homoptera, Cicadidae, Magicicada)” by J. E. Heath, “Combining Data from Citizen Scientists and Weather Stations to Define Emergence of Periodical Cicadas, Magicicada Davis spp. (Hemiptera: Cicadidae)” by M. J. Raupp, C. Sargent, N. Harding, and G. Kritsky. Gene Kritsky and Cicada Safari provided data used for the graphic of cicada emergence in 2020. We also thank Chris Simon for sharing her lecture notes of cicada development underground, Chris Maier for his studies of cicada biology, and John Cooley for enlightening discussions.

To learn more about periodical cicadas, please visit the Cicada Crew website at the University of Maryland.

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In the past month, we peeked underground to see what periodical cicada nymphs were up to, untangled the misconception that cicadas are locusts, and learned to recognize signs of cicada activity by observing exit holes and excavations in landscapes created by foxes, raccoons, dogs, and other mammals. Recently, the most frequently asked question about periodical cicadas is “when will cicadas appear.” Bug of the Week has been tracking the life history of periodical cicadas for almost two decades so let’s look at some historical data and see what it reveals.

At the last emergence of Brood X way back in 2004, in University Park, MD, the first cicadas were up and out of the ground on May 6. University Park is a suburb just a few miles from a major urban heat island called Washington, DC. About 20 miles further north in less urbanized and cooler Columbia, MD, the big jail break happened a full nine days later on May 15, 2004 beneath an ancient crabapple tree in my front yard. It is well known that emergence dates of periodical cicadas can vary over relatively short geographic distances due to variation in exposure to the warmth of sunlight on the ground and local temperature regimes. In different locations, soil temperatures hit the magic 64 degrees Fahrenheit on different days. A soil temperature of roughly 64ᵒF is the proximate cue that the world above ground is now warm enough for cicadas to emerge, shed their skin, best hungry predators, climb to the treetops, and begin the awesome task of finding a mate and fulfilling the biological imperative to reproduce.

How can we tell when the big jailbreak is close at hand? The images and video accompanying this episode provide some clues. For the last several weeks, we witnessed almost-ready-to-go periodical cicadas peeking out from their galleries. In these images, notice that just behind its brilliant vermillion eyes, the dorsal surface of the cicada’s exoskeleton is uniformly tan in color. On the evening or day of emergence, notice how the exoskeleton of the cicada bears two jet-black patches just behind its eyes.  In more than a dozen emergences of periodical cicadas attended by the Bug Guy, this seems to be the clue that cicada emergence is very close at hand or underway. When you see these dark patches, the big show is about to begin.  

For seventeen years, nymphs of Brood X cicadas have been developing underground. While digging a hole in my yard in 2018, I discovered a quartet of periodical cicadas about 14 inches underground. Notice their white eyes and uniformly tan bodies. Last week, a periodical cicada not quite ready to emerge rested at the top of its exit gallery beneath a cinder block. Just behind its red eyes, the dorsal surface of the cicada is uniformly tan. On the evening of its emergence, notice how the dorsal exoskeleton of the fully developed cicada nymph bears two distinct black patches just behind its eyes.

In a previous episode of Bug of the Week in 2017, we reported sightings of impressive numbers of Brood X cicadas that appeared four years early. These cicadas are known as “stragglers.” Stragglers are periodical cicadas that emerge years prior to or after the major portion of their brood mates. Often, 17-year cicada stragglers emerge four years prior to the emergence date of rest of the brood. In 2017, Maryland Brood X stragglers appeared on May 14 in Columbia and Gaithersburg. In addition to emerging four years early, sometimes stragglers emerge one year early and this is exactly what happened in 2020.  Using data collected in 2020 from the brilliant Cicada Safari App, the very first cicada out of the ground was seen on April 19, just south of Towson, Maryland. This one was an extreme outlier. Cicada emergence really picked up in the DMV on May 14, and by May 24, 25% of emerging cicadas were out of the ground. By May 28, 50% of cicadas had emerged, and just few days later on May 31, 75% of all cicadas had emerged in DC, Maryland, and Northern Virginia. So, if 2021 is anything like 2020 or previous years for that matter, cicadas will be regularly seen as a trickle in our region in the first two weeks of May with a tsunami hitting in the last two weeks as these teenagers are up and out for the cicadapalooza. Here in the DMV in 2020, the last cicada to emerge was reported on June 14. Due to a normal life span of two to four weeks, don’t be surprised to see adult cicadas alive and well into the waning weeks of June, but, sadly, by the 4th of July, their moment in the sun will be all but finished and nothing but a fading memory. Remember, the great W. C. Fields once opined “Never work with children or animals” and I will add, especially with periodical cicadas, “or when it comes to weather”. When will we see cicadas in the DMV? Perhaps, we will just have to wait and see.

Acknowledgements

Bug of the Week thanks Scott and Jordana Snider for providing the inspiration for this episode. Three cool articles, “Combining data from citizen scientists and weather stations to define emergence of periodical cicadas, Magicicada Davis spp. (Hemiptera: Cicadidae)” by M. J. Raupp, C. Sargent, N. Harding, and G. Kritsky, “The ecology, behavior, and evolution of periodical cicadas” by K. S. Williams and C. Simon”, and “Thermal synchronization of emergence in periodical “17-year” cicadas (Homoptera, Cicadidae, Magicicada)” by J. E. Heath formed the foundation for this episode.

To learn more about periodical cicadas, please visit the Cicada Crew website at the University of Maryland.

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Two weeks ago we began a series on the upcoming appearance of Brood X cicadas and visited an almost ready to emerge member of the graduating class of 2021 in a shovelful of soil. Last week we learned that cicadas are not locusts. This week we’ll talk about all of the holes and other signs of cicadas that are popping up all over the place in the DMV. But first, let’s talk about the feast that is underway for small wild and domestic mammals as periodical cicadas prepare an exit strategy from their seventeen years underground. This feasting stage began almost two months ago when a curious homeowner sent fascinating images of impressive excavations of turf beneath a fine old tree. The perpetrator of this crime was a pesky raccoon intent on digging for its dinner. The lawn was, well, just collateral damage on the way to a fine meal.  While the identity of the subterranean morsel was never confirmed, this type of behavior is characteristic of many small mammals that will find cicada nymphs and adults irresistible this spring and go to great lengths to find them.

A couple of weeks ago while emptying some coffee grinds in the compost at 6:30 AM, I surprised a very handsome and healthy red fox in the process of excavating a thirty-foot-long patch of earth beneath my stately Burford holly. A couple quick turns of the shovel revealed several Magicicada nymphs about six inches below the surface of the earth. Casual site visits to my neighbors’ gardens and further inspection of my landscape revealed several locations where fox and friends have been busy in Columbia, Maryland. Both foxes and raccoons have excellent night vision, a must for their nocturnal forays, and an extremely keen sense of smell that allows them to detect prey beneath layers of fallen leaves and soil. These wild small mammals are not the only ones whose special creature powers include super olfaction. A dog’s sense of smell is estimated to by more than 10,000 times more acute than a human’s. And yes, this week several reports arrived to the Cicada Crew posing the question: “Why is the dog digging up my yard?” Chances are good that Fido knows a good snack when he smells one. Please, just don’t let him eat too many.

Beneath a maple tree a very dusty cicada peeks out of its hole, while beneath a concrete block another nymph shapes its gallery with clever forelegs before plunging back into the tunnel, avoiding the lens of the camera. 

Now is an excellent time for a suburban safari to your backyard to spot signs of the arrival of periodical cicadas, which could happen sometime soon. Look for holes in the soil about the size of a dime within the dripline beneath trees that have been in the ground for seventeen years or more. Oak, maples, crabapples, and hollies seem to be the big winners in my landscape at the moment. In addition to holes, periodical cicadas often build domed caps known as turrets over their escape tunnels. This may be more common in wetter soils. If your landscape includes stepping stones or slate pathways over soil, lift a few and you may discover lateral tunnels as cicadas encounter the impenetrable barrier and attempt to make their way to the edge of the barricade to reach the world above ground.

No holes under trees? Don’t panic, new holes are showing up in landscapes on a daily basis.  Reports of cicada nymphs above ground are also arriving. In fact, while raking up leaves and branches yesterday, I unearthed several nymphs that must have been dislodged from the soil as I removed the leafy layer above their galleries. Coloration of their exoskeleton indicated that they were not quite ready to make the jailbreak from the earth. I returned them to the soil. Recently, someone asked how cicadas moved about underground and how did they construct their exit galleries? The answer is clever adaptations. Their forelegs bear greatly expanded femurs and tibias which act like the blade of a shovel to move soil. Millions of years of evolution for a life in two worlds, one underground and one above the earth, have perfected the tools necessary for cicadas to succeed in both.        

Acknowledgements

Bug of the Week thanks L. Kenigsberg for providing the nice image of lawn pillaged by a raccoon that served as the inspiration for this episode. Kristin Jayd and Paula Shrewsbury also provided images and assisted with videography.       

Join The Bug Guy tonight for an in-depth Zoom event with the Prince Georges County Alumni Network: Return of Periodical Cicadas – Fear, Fascination and Fun in 2021. University of Maryland Professor Emeritus Mike Raupp will explore the natural history, ecology, and behavior of the seven species of periodical cicadas indigenous to North America. Preregistration required.

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Last week we visited Brood X periodical cicada nymphs preparing to exit the earth after a 17-year interment underground. This week let’s settle the score on an often-asked question about cicadas, “Are they locusts?” The notion that periodical cicadas are a type of locust dates back to some of the earliest biologists and religious leaders struggling to understand the strange and unprecedented appearance of legions of large insects emerging from the earth every 17 years. In 1666 Henry Oldenberg, a German theologian and natural historian was, perhaps, the first to note the peculiar similarity between periodical cicadas in North America and biblical plagues of locusts which occurred periodically in parts of Eurasia. Oldenberg referred to the cicadas as “flyes” rather than locusts. Some 49 years later in 1715, the Reverend Andreas Sandel of Philadelphia described cicadas as “locusts”, noting that this was the vernacular name given to these creatures in the English colonies. But his reference to locusts was not to the eighth biblical plague of Egypt; rather, his allusion was to the fact that Native Americans consumed cicadas in much the same way that John the Baptist had eaten locusts. And so, Sandel concluded his account by stating “These locusts lasted not longer than up to June 10, and disappeared into the woods.”

We met lubber locusts in a previous episode of Bug of the Week. Locusts belong to an order of insects called Orthoptera and are members of the family Acrididae. Acridids are commonly called grasshoppers and these cosmopolitan insects number more than 10,000 species worldwide. Some, like the differential grasshopper, are common residents in landscapes where they munch flowers and vegetables. Others, like the migratory locust, Locusta migratoria, likely the real culprit of the eighth plague of Egypt, are widely distributed across several continents. They can attain astounding densities, become highly mobile, and use powerful jaws to devour vast swaths of vegetation as they rage across the earth.

Watch as a grasshopper uses its jaws to chew leaves of a small plant. Locusts are a type of grasshopper. By contrast, cicadas like this Brood X periodical cicada sip fluids with sucking mouthparts inserted into the vascular tissue of plants. Notice the sucking mouthparts point downward between the front legs of the cicada. Excess fluid from their liquid meals is excreted by cicadas. Tropical cicadas produce torrents of liquid waste as they feed. Fortunately for millions of folks who will be visited by periodical cicadas this year, Brood X does not generate cicada showers of this magnitude.

Periodical cicadas belong to an order of insects called the Hemiptera (true bugs). They are members of the family known as the Cicadidae. More than 3,000 species of cicadas inhabit the earth and they are found on all continents except Antarctica. However, the magical periodical cicadas occur only in the eastern half of the United States – lucky us. Periodical cicadas lack the biting jaws of locusts; instead, their mouthparts consist of a soda straw-like affair. Both nymphs and adults insert this proboscis into vascular tissue called xylem which is found in roots and stems of plants. Cicadas suck nutrients and water into their digestive tract with these mouthparts. Excess fluid is excreted from the digestive tracts of cicadas and there have been reports of folks standing beneath a tree loaded with cicadas who felt a gentle shower emanating from the tree above. When billions of cicadas are about, like John Fogerty crooned, you could see rain “commin’ down on a sunny day, yeah.”   

So, to answer the question, “are cicadas locusts?” Nope.

Acknowledgements

Bug of the Week thanks Gene Kritsky for providing the inspiration for this episode and acknowledges his wonderful book “Periodical Cicadas: The Plague and the Puzzle”, which was used as a reference for this episode. We also thank Dr. Shrewsbury for helping wrangle cicada nymphs featured in this and last week’s episode.

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