Monday, May 17, 2021

Natural Phenomena of This Spring ~ Anyone for Six Degrees of . . . Pehr Kalm?

This springtime for me has been marked by two events of nature.  The first is occurring just outside my backdoor where a cluster of Erigeron philadelphicus, commonly known as Philadelphia Fleabane or Common Fleabane, is thriving.  I first noticed the flowers in late April, and the flowers with their many subtle shades from white to light pink or pale magenta have multiplied over the past month.

This is a composite flower, with each flowerhead comprised of more than a hundred rays.  Among the distinguishing features of this flower is the way in which the leaves clasp the flower stalk.  Circled in the picture below is a leaf clasping the stem on one of the Common Fleabane plants in my yard.

These flowers are all volunteers, appearing unbidden.  (They do not have any particular power over fleas, despite their common name.)

The second event heralding this spring is one long expected, having been in the works for 17 years.  My area of the mid-Atlantic states is presently at or near one of the epicenters of the emergence of Brood X of the 17-year periodical cicadas:  Magicicada septendecim, M. cassini, and M. septendecula.  This particular appearance has been awaited with gleeful anticipation by many and with mounting dread by others.  Pictured below is, I believe, a specimen of M. septendecim I spotted recently.  (I should have turned it over to see the underside which is the key to distinguishing among these species.)

In keeping with the past practice on this blog of finding some linkage connecting apparently distinct phenomena, I played the game of "connect the natural phenomena" (à la “Six Degrees of Kevin Bacon” (see Wikipedia article)).  Somewhat to my surprise, I found a good candidate quickly and easily to tie the budding forth of E. philadelphicus to the impending onslaught of Magicicada.  The key is that the full scientific name of the Common or Philadelphia Fleabane is Erigeron philadelphicus L.  That “L.” is the hook.

The Swedish naturalist Carl Linnaeus (1707-1778), to whom we owe the use of binomial nomenclature  to identify organisms, is the authority for the scientific name of this flower (hence, the “L” after the genus and species).  Linnaeus identified and named this flower species in volume II of his 1753 Species Plantarum.  In his first stab at it he made the species name neuter, calling it philadelphicum.  To fit with the masculine genus name, the species name was later changed to the male:  philadelphicus.  

Erigeron, the genus name, is a bit whimsical, coming from two Greek roots:  eri meaning “early,” and geron meaning “old man.”  The Missouri Botanical Garden entry for the Common Fleabane states that these two Greek terms refer to the plant’s “early bloom time and downy plant appearance suggestive of the white beard of an old man.”  An early old man?  Well, for the E. philadelphicus, I would demur; there is much that is young and vigorous about these flowers as they wave happily in a spring wind.

As to the species name, it certainly refers to the city of Philadelphia.  But why?  It’s found there, but not there in particular, and wasn’t back when Linnaeus named it.  A clue lies in Linnaeus’ description of E. philadelphicus in which he noted:  “Habitat in Canada.  Kalm.”  So, the apparent location of this flower was in “Canada” and the person who collected the specimen was named Kalm.

The “Canada” to which Linnaeus referred is not synonymous with today’s Canada.  Botanist Gerry Moore, in a detailed article about scientific names that honor Philadelphia, quotes botanist William Thomas Stearn on this point:  Linnaeus considered Canada to be “a region of northeastern America, partly in [present day] Canada, mostly in the United States where Kalm did much collecting, i.e., roughly from Philadelphia and New York northward . . . .”  (An Overview of Scientific Names Honoring the City of Philadelphia, Pennsylvania, with an Emphasis on Flowering Plants,” Bartonia, Number 69, 2016, p. 93.)

Pehr Kalm (1716-1779), the collector cited by Linnaeus, was one of his early pupils who spent several years in North America collecting plants and observing natural history.  Kalm was born in Sweden to Finnish parents who had fled Finland during the Great Northern War.  He studied with Linnaeus and, under the aegis of the Royal Swedish Academy of Science, traveled to North America in 1749 with the mission of gathering plants that might be successfully planted in Scandinavia.  Kalm stayed in North America until 1751, spending much of the time in the Philadelphia area with a couple of excursions north into Canada.  Among the products resulting from his time on this side of the Atlantic was a multi-volume account of his travels.  Presumably among the plants he collected and carried back to Linnaeus was E. philadelphicus.  In his multi-part history of the ecological sciences, historian Frank N. Egerton described the work of naturalists who visited North America early in its European settlement.  Kalm, he wrote, was “[p]robably the best educated explorer naturalist who came to America in the 1700s.”  (A History of the Ecological Science.  Part 22:  Early European Naturalists in Eastern North America, Bulletin of the Ecological Society of America, Volume 87, Number 4, October 2006.)

How do cicadas connect to Kalm?  Fortunately, the year he arrived in North America, 1749, was one of those magical years when millions of Brood X members emerge and launch into an ear-splitting, cacophonous symphony.  [Later edit:  should have written "billions" of course.]  He was seeing and hearing insects whose descendants, 16 generations later, are now bursting onto the scene in 2021.  After his return to Europe, Kalm penned one of the earliest accounts of the 17-year periodical cicadas, an article with the misleading title Description of a Type of Grasshopper in North America.  It was published in a Swedish journal in 1756.  (Pehr Kalm’s Description of the Periodical Cicada, Magicicada Septendecim L., The Ohio Journal of Science, Volume 53, Number 3, May 1953.)

Despite the title of the article, it’s evident that Kalm knew that the insect he observed in 1749 was a cicada, not a grasshopper.  When he came to write this article several years later, he was quite clearly still aghast at what he had observed and heard.  To these insects as a whole, he applied the adjective “extraordinary.”  To the number of them appearing that spring in 1749, he went for vivid and emotional descriptors:  “astounding,” “dreadful,” “fantastic,” and “shocking.”

Kalm did some historical research through church records and determined that these insects followed a 17-year cycle.  As to the range of these periodical cicadas, Kalm observed

A peculiarity of these insects is that they do not emerge simultaneously in such shocking quantities in all places.  For example, the year the whole of Pennsylvania was swarming with them, not a single one was head of in New England.  This was also true of other localities.  When I left Pennsylvania in May, 1749, I was afraid my ears would be ruined by the noise and the disturbance they made in the trees.  The same hum and din reverberated in the woods in part of New Jersey, but as I travelled toward New York the noise diminished.  Beyond Albany, I head only an occasional one, and I frequently travelled a whole day with hearing any.  The inhabitation of Albany had not heard any more than usual.  It was nine years since their last heavy infestation.

I have been using the smartphone app Cicada Safari,created by entomologist Gene Kritsky and the IT department at Mount St. Joseph University, to do my bit in a citizen-science project chronicling the emergence of Brood X.  Among the pieces of background information presented in the app is the map below showing the disparate areas in which clusters of Brood X are appearing.

Yes, Kalm had it right.  There is a distinct regionality to the appearance of this particular brood of Magicicada.

So there it is:  a completed game of “connect the natural phenomena”: 

Erigeron philadelphicus to Pehr Kalm to Magicicada septendecim.

I avoided the easiest path and didn’t simply use Linnaeus himself to make the link.  There’s no challenge to that since his name is associated with every organism that has been given a scientific name, even if he wasn’t the one who first named it.  That said, Pehr Kalm appeared as a gift from heaven.  Had he travelled to North America a year earlier or a year later, the game might have not ended so quickly and neatly.

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