Unique Cicada Cycles

The tall trees on the stately lawn of my grandparents’ farmstead supplied unmatched opportunities for children to collect spent “dog day” cicada shells. This common cicada variety is familiar to virtually everyone. We hear them every summer during August. There are many species of dog day cicadas which are barely distinguishable from each other except for their subtle singing variations and slight differences in appearance. The crisp, empty cicada shells supplied young people with childhood joy and plentiful “treasure.” Even more exciting was discovery of an emerging adult before it ascended to the tree tops to serenade the neighborhood for a few weeks.

Of nearly 3000 cicada species worldwide, only three species comprise the 17-year periodical cicada variety now receiving publicity as they emerge from the ground solely in the eastern United States. The unique timing ability of this creature is a rarity among cicadas worldwide. These three cicada species are included among the estimated six to ten million insect species on our planet. These millions of diverse species represent approximately 90% of all animal life. The extraordinary notoriety surrounding the 17-year periodical cicada is entirely warranted.

After remaining underground for 17 years, billions and billions of cicadas emerge when the temperature reaches 64˚F in their 17^th summer. It is the longest-lived insect in North America, having tunneled underground out of sight while feeding on sap from tree roots. I have personally experienced three Brood II east coast emergences of the 17-year cicadas—1962, 1979, and 1996. In 2007 I also observed the singing of thousands of the same 17-year variety at our home in Illinois. It was Brood XIII, one of twelve broods in the US which overlap other 17-year broods. Most years the 17-year species emerges somewhere in the eastern United States. There are three or four “major” broods. The largest brood, dubbed Brood X, emerged in 2004 in 15 eastern states.

As if the 17-year cicada scenario were not interesting enough, there are several other cicada species which form three broods of 13-year cicadas. This variety’s counting ability stops at 13. The largest of the three broods, Brood XIX, last emerged in 2011 in 16 states including Illinois. The remaining two broods will not reappear until 2014 and 2015. In 2011, I believe I heard the faint songs of a few 13-year cicadas for a few days.

How do periodical cicadas keep track of their years underground? Some experimenters have attempted to fool a few laboratory specimens transplanted from the wild by forcing rooted indoor fruit trees to blossom twice per year. Apparently a few laboratory cicadas were tricked into emerging early. The insects, however, were still able to count fruiting cycles. Their mathematical talent for counting 17 cycles was still present in the insects. Beyond this, their ability to apply a difficult mathematical skill is still a mystery to scientists, but the ability is unquestionably programmed into the cicada’s genetic DNA blueprint.

Genetically programmed traits are ubiquitous in living things. Discussion of innate genetic markers and their relationship to the manifestation of physical traits is the subject of abundant research among scientists. Genetic traits also provide the organism with ability to acquire a multitude of learned behaviors. Base pair arrangement of molecules in DNA is responsible. This explanation is accurate and simple, but still inadequate: We translate the physical arrangement of molecular elements such as base pairs to time intervals of 17 or 13 years in periodical cicadas. But how could this be? Scientists do not know. The answer is in the omniscient mind of the Creator.

Lost Timekeepers

Recently my treasured wristwatch disappeared. It belonged to my father who passed to eternal life in 1999. I had claimed this watch as my own and wore it frequently. My thorough searches around the house proved fruitless. The clasp had failed, I reasoned, perhaps as I was mowing grass or visiting local stores. A week later my wife approached me and asked, “Guess what I found?” She had located the watch in a pair of shorts I had not checked!

Over the last two weeks many object lessons concerning the watch occurred to me. For example, the timepiece was out of sight but keeping perfect time in an unknown place. Its time keeping ability was undiminished. The watch batteries could have functioned perfectly for several years based on its inner mechanisms. It had been programmed to function silently and with precision waiting for the time when it would “make its reappearance.”

Several internet stories lately provided a punch line for this object lesson from the animal world. The world of insects provides us with a spectacular example of inherent time keeping ability. We speak of the amazing saga of the periodical cicada. Most people have heard of the 17-year cicada but the story of the underground timekeeper is retold to renewed enthrallment, especially whenever they make their infrequent appearance. This insect has a life cycle of exactly 17 years. It emerges from its underground haunts on cue to supply many of our country’s residents with fascination, and in some cases entomophobic dread. Uncounted millions of insects emerge to serenade residents with a cacophonous, ear-splitting symphony after rehearsing for their concert beneath the surface undetected for 17 years.

Before we highlight some of the more remarkable details of this insect in future posts, I recall some personal experiences with these creatures going back 51 years. The progression of events places the periodical cicada saga in sharp personal perspective. Memories of each “Brood II” emergence connect strongly with significant events in my life’s chronology. There are twelve broods of periodical cicadas in the eastern half of the US. Their 17-year cycles overlap with each other chronologically and geographically. Brood II is one of the three most significant emergences and is highlighted in newspaper accounts whenever it occurs. As we write, Brood II is breaking forth from their subterranean lairs in Northern New Jersey where I spent my entire teaching career.

In 1962 I was a recent hire on an early secondary school science staff. Rumors had circulated that the 17-year cicadas were emerging. On my assignment to noon-time recreation supervision, I recall the din of cicada songs originating about a quarter mile away and called it to the attention of students. That same spring I used the church bus to gather a large group of 9-11 year old boys for a church class picnic. Having been apprised that the cicadas were singing from a pocket of woods a mile away, at the conclusion of the class softball game I loaded the boys into the bus for a journey to the location of the insect concert. We all had “front row seats.”

In 1979 our son was three years old. Most little boys are fascinated with bugs, but not large, bug-eyed, winged creatures crawling up their clothing while producing intermittent buzzing noises. That adventure in the county park held high fascination for his parents, but not for our son Brad.

In 1996 20-year old Brad returned home to New Jersey from an out-of-state college for summer break. I had warned him that he was in line for a memory throwback. We journeyed over to the same park we had visited in 1979. This time we enjoyed the cicada symphony, even catching some specimens and letting them crawl on our arms and our car’s dashboard. My science classes enjoyed a brief video clip of their teacher’s cicada throwback visit to Lewis Morris County Park.

In 2013 the local newspapers in New Jersey are filled with feature articles of this spring’s cicada onslaught. I will miss my fourth consecutive first hand experience of this particular display of billions of God’s unique insects. Only three species of 17-year cicadas exist. There are, however, over 2500 cicada species worldwide. In the creativity of our Maker, He saw fit to endow only a few species with this talent for timekeeping. In humor, I wonder if the 17-year cicadas provide object lessons for wristwatches—lost and out of sight, then found and still keeping perfect time.

North American Discovery

Discovery Channel has broadcast the first of its newest nature blockbusters. North America highlights 110 different North American species with startling HD photography. Three years in preparation, its venues range from mountains to plains, from the Arctic to the Tropics, from sky to land to sea, from punishing heat to chilling cold, and from tranquil to violent weather. The wonders of nature on our home continent may hold even greater appeal than the wonders of previous productions Planet Earth, Frozen Planet, and Africa. These natural wonders have significantly retreated from our awareness owing to our incessant focus on technological gadgets feeding, among other things, our sense of materialism and social networking. The last-mentioned dimension of our modern experience is a discussion topic with a completely different focus.

The unusual beauty and behavioral habits of the many species highlighted on North America will no doubt become a spectacular media success on many fronts. The intelligence of the animals and their unique environmental adaptations contribute to enjoyment of their life’s challenges, often in pursuit of food or a mate. Some animals use their intelligence to avoid becoming another creature’s meal. The producers portray the sensitivity of the animals, imposing an anthropomorphism sometimes termed “soulishness” by commentators on animal life. This characteristic, when used in connection with the animal world by scholar Hugh Ross, is defined as “the endowment of mind, will, and emotions in order that these creatures may form relationships with members of their own species as well as with human beings.”

If there is any valid commentary on such media specials, perhaps it could come in this form: The implication that the animals must manifest highly stunning or spectacular traits is reasonable if a producer wants to maximize program viewership. The striking grandeur of animal behavior, weather events, or the beauty of our cosmos are sometimes topics of biblical authors in Job, the Psalms, and other scriptures. We may infer that there are more sources of wonder which are arguably less remarkable, but nevertheless fully worthy of our focus. In our entertainment culture, perhaps we should search for the remarkable in more ordinary, mundane events. Such a search may result in our best defense against boredom!

Just after the glorious spring arrival of tree leaf-out in May, I imagined what my personal North America special would highlight. Our cold, snowy winter is a distant memory. In my neighborhood, the annual May leaf-out of forests has arrived one month later than last year. Our regional farmers have attempted to make up time lost to a cool, rainy spring by using the headlights on their equipment to plant this year’s corn and beans in the dark.

In my residential neighborhood, I have taken note of the recent arrival of our migrant bird population. In particular, I’ve researched the most familiar recent arrivals and where those avian “snow birds” spent their winters. Starting with the scarlet tanager--one flashy male sang next door from the very top of a lofty dead oak branch. He had never before favored us with a visit to our immediate neighborhood, at least not where I could spot him. He had wintered in Mexico or Central America. Many other arrivals had made use of the same wintering spot: Baltimore orioles, rose-breasted grosbeaks, and catbirds. Barn swallows all wintered in South America. Indigo buntings and towhees have yet to return from their wintering grounds. The navigation skills of these departing and returning migrants, the monogamous behavior of many species, and their ability to return to the same neighborhood year after year ranks them high on my catalog of remarkable feats.

Our monogamous cardinal pair remained all winter, usually keeping each other company. This spring they even sang on occasion during the darkest night. Groups of bluebirds, robins, purple finches, and goldfinches are year-round or partial migrants. Woodpeckers and owls stay all year, drumming, or hooting. The last report in our personal North America neighborhood special consists of details of a spectacular spring display of wild turkeys on our street. In past years the tom turkeys have taken to displaying their impressive fans on our lawn. Last week six males displayed their fans in a lengthy ritual courtship demonstration for two females in the middle of our sparsely traveled street. Other species of birds visit all year or seasonally. They didn’t make it to this listing.

The six or seven dozen bird species I have spotted (some neighbors have identified far more) impress us with their distinctive appearance and many unique behaviors and songs. Each species makes a special contribution to my personal chronicle entitled “North America of Northern Illinois” for readers around the country. It is one of my many reasons to worship the Lord of all Creation on a daily basis. 

 

  

Heat Balances

Some people may suspect our post title, Heat Balances, suggests a discussion of heavier science than they prefer. The scientific dimension of the earth’s heat balances may not seem interesting in ordinary conversation with our friends. Instead, we may speak about how cool or warm we keep our homes, or cold or hot it has been outdoors lately.

How much effort do we devote to pursuit of personal temperature comfort? What low-end to high-end temperature range would most people claim as their personal comfort level? Without bundling up in a sweater or peeling off clothing back to bare arm conditions, what is the temperature range at which you feel comfortable? When I posed this question to my wife, we agreed that a 6˚F range provides the extreme limits. Beyond this, our indoor comfort level demands either bundling up in a sweater or baring our arms. Outdoors, the range may be greater because of breezes or sunshine. Most would agree that the human body is tolerant of only a few degrees of temperature range, depending on how long we remain in a room and what our activities are.

Our personal body systems have been created with provisions for maintaining a satisfactory heat balance. Apart from the tendency of humans to add or remove clothing, our bodies have the ability to sweat when we become overheated. Animals use a variety of other strategies to maintain a comfortable heat balance. None are known to wear exterior clothing, and perspiring is practically unknown in the world of animals. Humans, in contrast, after removing outer clothing or ramping down their activity level, have only one other natural defense against overheating, apart from retreating to the comfort of human-engineered air conditioning systems. It is called perspiring. Of course, health warnings about drinking fluids and other precautions should be observed.

What is the secret success of sweating for the human? Sweating is a markedly human trait. So is putting on articles of clothing and the desire to remove them. Design and volitional use of clothing is a distinctly intelligence-enabled human trait. Perspiring appears to be a divinely authored adaptation uniquely available to humanity from the beginning. A trait called the latent heat of vaporization is responsible. Quantitatively, 540 cal/g is the heat of vaporization. For each gram of water that vaporizes, 540 calories of heat must be absorbed. An enormous amount of heat is quickly removed from our bodies. More evaporation of perspiration results in more cooling. Our body loses heat; we feel cooler. When our bodies are overheated the inability to lose heat could be hazardous or even fatal.

Taking a giant leap from everyday human comfort to the broad topic of the continual inflow and outflow of heat on our planet, we discover earth’s mechanisms for heat balance are important physical phenomena. The global balance of incoming heat from the sun and the outflowing of heat from earth back to space is of interest to physical scientists. The earth has many systems to distribute the heat it gains in a manner beneficial to life on this planet. Apart from the effects of ocean and atmosphere, earth’s heat balance would be simpler to understand. Life on earth, of course, would be impossible without water and air. Water and air are tremendous storehouses, constantly giving up, absorbing, distributing, and balancing their store of heat.

In the past few decades climatologists have become more aware of changing ocean circulation patterns which affect the global distribution of heat in the atmosphere. These patterns of circulation are termed “oscillations.” They recur periodically, bringing with them a few degrees of change in ocean temperature over large areas of our water-covered globe. Subsequently, earth’s atmosphere is warmed or cooled to some degree. In our recent post entitled “Weather-caused Humility” we discussed the effect of evaporation of liquid water into vapor and its effect on the transfer of atmospheric heat over long distances. Of course, the more obvious transfer occurs when rainfall reaches us from water vapor originating hundreds or thousands of miles away in the ocean.

Climatologists have discovered and explained the ENSO (El Nino Southern Oscillation), the PDO (Pacific Decadal Oscillation), and the AMO (Atlantic Multi-decadal Oscillation). These variations cause significant episodic changes in ocean and air temperature. Atmospheric temperature swings are due not only to contact with warmer or colder water, but also from evaporation rates resulting in warming of the air. The changes result in significant weather variations over a few years, over a few decades, or even longer. One wonders what sort of ocean oscillations triggered the megadroughts across America during the past 1000 years. What caused desert-like conditions to spread across the Great Plains, including the formations of sand dunes still visible in some areas such as Nebraska?

Our awareness of the perspiration phenomenon from the human body may inspire inquiry into more extensive heat balance processes occurring on our earth. If I were to return to the classroom to teach a lesson on heat balance, I would consider introducing the topic with a discussion of--of all things--human perspiration! Many wonders of our daily environment operate within a diverse set of physical laws. Our Creator authored these laws and provided them for our welfare, awareness, and enjoyment.

Weather Math

Each morning brings gifts from God in many facets. Our ability to become a non-professional atmospheric scientist while expending minimal time in formal preparation is one of those gifts. Expressed another way, everyone can be an armchair weather observer. Weather statistics are often part of our observations. One of the first questions to be answered each morning is, “What is the temperature?"  Meteorology is one of several science topics for which I discovered an early fascination. Its reality is effortlessly accessible whether we are indoors or outdoors. Weather events provide a ready-made topic of conversation, supply opportunity to hone observational skills, and supply occasion for light-hearted commentary.

A few of my former class members may have become professional

meteorologists because of their early fascination with the weather. Perhaps they were captivated by the thermographs and barographs we used to automatically record temperatures and barometer readings a week at a time on revolving drums with an ink stylus. One of my former students possessed a truly unique fascination with weather. I still have a vivid memory of Kevin passing my room and poking his head into my open classroom doorway while we were watching Weather Channel radar images approaching a few miles to our west. Kevin made no secret of his love for weather topics. Another embedded memory occurred when huge, golf-ball sized snowflakes began to fall during one science class. “Quickly, put on your coats…I’ll meet you all just outside the exit door downstairs.” The flakes were easily “catchable” in the students’ mouths. It became an impromptu recess. The next day’s newspaper carried accounts of the event. One student gratefully reminded me of that incident several times before the school year ended.

Rarely some of my students would complain that they found a certain activity “boring.” Sometimes this related to the mathematics necessary to quantify their science discoveries. I developed an appropriate comeback for this common lament. I asked them “Are you boring?” The effect of my question was somewhat curative. In the long run, young people need to learn the fascination inherent in more ordinary things and events surrounding them. With thoughtful engagement, perhaps our children could learn that even mundane events deserve a share of their attention. Mathematical skills may hold some degree of fascination even for students and adults who avow dislike for math. Teachers and parents should work in tandem to help young people discover interest-inspiring activities in everyday situations. This idealized goal is achievable, but young and old must work at their objective.

Most adults may not fully understand certain regularly used weather terms. We refer to humidity--the water vapor present in the air. The air surrounding us includes water in vapor form. “Absolute humidity” relates to the ratio of mass of water vapor/m³ of air. At maximum, air holds just a few grams of water vapor/m³ of air. One m³ of air has a mass of approximately 1.3 kg. The percentage of water vapor in air varies between 0% and 4%, generally on the lower end of this range. Usually, the 1.3 kg of air/m³ (1300 g, or 2.86 lb) contains only a few grams of water vapor, perhaps 30g at maximum. These terms and statistics, however, are never part of our friendly television weather journalist’s forecast for laypersons.

Another term and related statistic is commonly used by media forecasters--relative humidity. To understand this common weather forecaster’s term, we must dig somewhat deeper. To illustrate the meaning of relative humidity, let’s pretend we take an exam with one hundred questions. Classroom test scores are usually converted to percentage, meaning per hundred. If we answer 75 correctly, our score is 75%.  Likewise, on a 20 question test, our score for 15 correct would also be converted to a percentage score of 75%.

When the local forecaster reports the relative humidity as 75%, he means that at the present temperature, the air contains 75% of the amount of water vapor necessary to saturate the air. The percentage is calculated by dividing the numerator (actual quantity) by the denominator (possible quantity). The key is understanding the meaning of “at the present temperature,” because when the temperature becomes warmer or cooler, the carrying capacity of air in terms of how much water vapor could be present also changes. Warm air is able to “hold” more water vapor than cold air; cold air is able to hold less. (Some writers object to the term “hold” in this context. Older books use the term as a conceptual aid.) A useful analogy is possible using a porous sponge. When it contains 75% of the water necessary to saturate it, we see that it could hold a little more. In the case of this sponge, if we fill it to 100% of capacity and try to add more, some liquid water will not be able to enter the sponge. It is 100% full. Another way to expel water is to reduce the carrying capacity of the sponge by squeezing it into a smaller volume. Squeezing the sponge reduces its carrying capacity, but it may still be regarded as 100% full.

In connection with the previous paragraph, we cite one more intriguing fact about relative humidity. A graphic representation of relative humidity over 24 hours almost always shows the relative humidity in the warmest part of the day is lowest. It is highest in the coolest hours around dawn. This phenomenon relates most closely to the carrying capacity of warm air (highest) and cool air (lowest). The actual amount of water vapor remains the same, but the temperature changes. Over a few days, additional water vapor could be added or subtracted to the air by arrival of distant air masses. The relative humidity could rise or fall, but for a different reason. Relative humidity would rise if the fraction’s numerator increases; it would fall if the denominator increases.

Perhaps readers have discovered more about weather math than they wanted to know. Mathematics is a divine gift which helps God’s children make sense of the world. We recognize greater or lesser mathematical gifts in every human. The world is more comprehensible through application of mathematics. Our ability to rationally quantify our world’s phenomena helps us understand the world as an orderly place because of our inherent mathematical aptitude. God created an orderly cosmos which reflects his character. Our earliest morning thoughts should include recognition of God as Creator of an ordered cosmos.

Weather-caused Humility

Personal preparation for this post included searching for written quotations concerning weather. One eye-catcher affirmed my belief that light conversational banter about weather often exceeds actual understanding of the topic: “Don’t knock the weather; nine-tenths of the people couldn’t start a conversation if it didn’t change once in a while,” humorist Kin Hubbard (1868-1930) observed.

Weather was a staple of earth science courses in my classroom. My challenge was to shift the topic from mere observation to an exercise in comprehension. I hoped to instill a sense of wonder along with an understanding of weather’s dynamic processes. Weather supplies us with a great deal of knowledge about the physical events surrounding us. For instance, in order for precipitation to occur, liquid water must first evaporate into water vapor before it supplies rainfall at a distant location.

Students wondered, “What more is there to know?” When our science students first became aware of the phenomenon of water evaporating from liquid to gas, then back to liquid at a different location, that was only part of the story. I reminded them of a common swimming pool event: Climbing out of a swimming pool with wet skin into the warm sun can be a surprisingly chilly experience. The cold shivers belie the comfort of swimming in the heated pool water. Understanding the cooling phenomenon helped them grasp some hidden wonders of our earth’s weather machine.

The process of evaporating water consumes a tremendous amount of heat. When water evaporates from our moist skin, it uses up body heat. Then we feel cold. Heat from the evaporation process is removed with the water vapor. In this case, the body’s heat energy is necessary to break the hydrogen bonds holding the water molecules close together in the liquid state. When the water molecules break free from each other, the distance between them is increased by thousands of times. In my classroom I explained that to scatter any sort of matter, such as a pile of marbles, into a larger space, energy must be used up. In the swimming pool example heat energy is used up from our skin. Scientists call the heat energy needed for this process latent heat of vaporization.

As evaporation takes place from large water bodies and travels long distances, large quantities of heat travel along with it. Eventually warm moist air rises to cooler levels of the atmosphere. Cooling the air causes the warm, moist air to condense back into drops of water. Heat is given back into the air once more as water drops form. This heat is called latent heat of condensation, the opposite process of latent heat of vaporization. This causes the heated air to expand, become lighter again and rise to even cooler elevations. The condensation process repeats several times, giving heat back into the atmosphere each time. Ultimately the process is finished, but not before some seasonal thunderstorms bring lightning, thunder, wind, and heavy rain to the area. Living in the Midwest sometimes brings with it the “right of passage” of severe weather experiences.

Our weather systems are ultimately driven by heat energy from the sun falling unequally on some latitudes more directly than others. In turn, the earth’s heat balance is tuned by the wonderful processes of heat distribution we have described. Life-sustaining precipitation depends on the atmosphere’s ability to distribute water vapor and heat energy widely. We depend on “normal” rainfall for our geographic areas to supply moisture for normal regional crops. Many weather experts preach that there is hardly a normal or average for any given day. Normal or average weather is a mélange of above and below average conditions blended with the truly beautiful, the unusual, the inconvenient, and sometimes the disastrous.

After reading the inspiring chapters of Job 36-38, one may experience a feeling of genuine humility in response to our life-sustaining planetary weather system. Some descriptions of weather events in Job are inspiring for their beauty. Others are genuinely frightening. The account of weather in Psalm 29 strikes terror as we are exhorted to “Ascribe to the Lord the glory due his name…” The author of Job 42 recounts the worshipful humility of Job after contemplating the wonder of God in nature, especially in weather events: “I know that you can do all things; no plan of yours can be thwarted. You asked, ‘Who is this that obscures my counsel without knowledge?’ Surely I spoke of things I did not understand, things too wonderful for me to know. You said, ‘Listen now, and I will speak; I will question you, and you shall answer me.’ My ears had heard of you but now my eyes have seen you. Therefore I despise myself and repent in dust and ashes.” (Job 42:2-6 NIV)