Fleas

Nearly a century and a half before Lewis and Clark’s encounter with fleas en masse on the lower Columbia River, and almost another century before the species acquired its reputation as an accomplice in some of nature’s most dreadful plagues, the little insect acquired for its kind an almost admirable, if not respectable, reputation, thanks to one man and his own remarkable instrument. The man was a 17th-century British polymath named Robert Hooke; the instrument was his own personal one-of-a-kind microscope. The principles and purposes of the microscope have been traced back more than four thousand years, but its name—from the Greek micron, meaning “small,” and skopein, meaning “to view”—was coined in 1624 by the German botanist and curator of the Vatican’s botanical garden, Giovanni Faber (1574-1629). In that same year Galileo Galilei (1564–1642), who is credited with having basically improved the instrument, wrote to the pioneer Italian naturalist Federico Cesi (1585–1630) that he had “contemplated very many small little animals with infinite admiration,” including a mosquito and a moth—which struck him as beautiful—and a flea, which was “most horrid.” In short, he declared, through that instrument “the greatness of nature can be infinitely contemplated, and [we may now see] how subtly and with what unspeakable care she works.”^[5]Quoted in David Freedberg, The Eye of the Lynx: Galileo, his Friends, and the Beginnings of Modern Natural History (Chicago: University of Chicago Press, 2002), p. 151. Translated, letter from … Continue reading

The long list of other subjects in Hooke’s majestic volume included the point of “a sharp small needle,” the edge of a razor, sparks struck from a flint or steel, figures seen in bits of sand, gravel in urine, blue mold, an extreme closeup of moss, a poppy seed, a fly’s eye, and a fly’s feet, an ant, a mite and a louse.

The Beauty of Hooke’s Image

And that enormous image of a flea that everyone was talking about! Sure enough, there it was, in Scheme XXXIV (Plate 34). We can imagine the hubbub it provoked. Little children giggled over it. Proper ladies slammed the book shut with shudders and squeals of revulsion. Well-bred gentlemen frowned and leaned closer in morbid curiosity. Hooke himself was awestruck. “The strength and beauty of this small creature,” he began, “had it no other relation at all to man, would deserve a description.” And so he drew, and then engraved with his own hand, all that he could see through his magical lenses. Finally, he transcribed his insights—a few of them far in advance of his time—into words: “As for the beauty of it,” he wrote, it was “all over adorn’d with a curiously polish’d suit of sable Armour neatly jointed,” which would help it to resist the claws, paws, or fingers (but not the opposed thumbnails) of any host that might try to brush it off or squeeze it to death. Today that hard external shell is termed, with scientific clarity and precision, an exoskeleton.

Moreover, its “armour” was beset with “multitudes of sharp pinns, shap’d almost like Porcupine’s Quills, or bright conical Steel-bodkins [stilettoes].” The head, he continued,

is on either side beautify’d with a quick and round black eye, K behind each of which also appears a small cavity, L, in which he^[6]Hooke was unable to determine the gender of his specimen, so he was using “he” in the gender-neutral sense. seems to move to and fro a certain thin film beset with many small transparent hairs, which probably may be his ears; in the forepart of his head, between the two foreleggs, he has two small long jointed feelers, or rather smellers, MM, which have four joints, and are hairy, like those of several other creatures; between these, it has a small proboscis, or probe, NNO, that seems to consist of a tube NN, and a tongue or sucker^[7]Hence the name of the suctorial Order to which all 3,000 species of this insect belong: Siphonaptera. The first half of the name, “siphon,” is Latin name of a tube used for drawing … Continue reading O, which I have perceiv’d him to slip in and out. Besides these, it has also two chaps or biters [jawbones] PP, which are somewhat like those of an Ant, but I could not perceive them tooth’d; these were shap’d very like the blades of a pair of round top’d Scizers, and were opened and shut just after the same manner; with these Instruments does this little busie Creature bite and pierce the skin, and suck out the blood of an Animal, leaving the skin inflamed with a small round red spot.^[8]Micrographia, “Observation LIII. Of a Flea.”

It seemed impossible to observe how fleas could propagate more fleas simply through a mindless, biologically compulsive act of copulation, so Hooke said nothing of that. Besides, in the second half of the 17th century CE almost everyone still held fast to Aristotle’s 4th century BCE thesis that fleas were spontaneously generated out of dust and dirt.^[9]The abbreviation CE stands for “Common Era,” while BCE stands for “Before Common Era.” They serve to replace AD (anno Domini, Latin for “in the year of the Lord”) … Continue reading

Powerful Legs

Above all, what was so unusual about the flea was that it could leap so far—13 inches (33 cm)—and so high—7 inches (18 cm)—without wings. Hooke was bold enough to assume that the solution to that conundrum could be found through a thoughtful examination of a flea’s external anatomy. On that premise, he continued:

the Microscope is able to make no greater discoveries of it then the naked eye, but onely [sic] the curious contrivance of its leggs [DD EE GG HH & I] and joints . . . is very plainly manifested, such as no other creature, I have yet observ’d, has any thing like it; for the joints of it are so adapted, that he can as ’twere, fold them short one within another, and suddenly stretch, or spring them out to their whole length.^[10]Ibid., “Observation LIII, Of a Flea.”

Yes, he was mistaken, but his argument seemed credible enough that it remained unchallenged for another 300 years. Then, in 1967, the truth began to emerge: The energy a flea needs in order to leap high and far is stored in a pad of highly resilient protein called resilin; the pad is located where the legs are attached to the body. But another 44 years elapsed before it was discovered through high-speed imaging, mathematical modeling, and scanning electron microscopy, that the flea applies resilin’s force to the ground through its shins (tibiæ; TIB-ee-eye) and toes (See figure above).^[11]Gregory P. Sutton and Malcolm Burrows, “Biomechanics of jumping in the flea,” Journal of Experimental Biology, 16 November 2010. Sutton and Burrows are zoologists at the University of … Continue reading

Pulex irritans

Eventually, Hooke’s flea was recognized as a reasonably accurate depiction of a female of the species that specifically prefers human blood, even though nobody in the 1660s had any reason to suppose there were more species in existence. Indeed, almost a hundred years later, Carl Linnæus (1707–1778) knew of only two, the 1-millimeter-long flea native to beaches in Latin America and the Caribbean, now called Tunga penetrans (“sand flea” or “chigger”) and one that resembled Hooke’s, to which Linnæus assigned the binomial Pulex irritans (“irritating flea”) in the Tenth Edition (1758) of his Systema Naturæ. His P. irritans was universally regarded in those days as a bothersome but benign species that vexed every living animal, human or otherwise, and the worst was that it clearly thrived on filth of any sort. 

The taxonomy—scientific naming, formal description and orderly classification—of insects in general grew very slowly during the 18th and 19th centuries. Despite the notoriety of Hooke’s microscopial exposé, and the fact that there was hardly a warm-blooded bare skinned, furred or feathered creature on earth that was not intimately acquainted with that notorious one-trick bug, the flea drew little if any serious attention from early entomologists. It was cast aside in favor of the study of more attractive insects such as moths and butterflies, or of agriculturally harmful species such as beetles, locusts, fruit flies and the tiny but devastating Hessian wheat fly. It is small wonder that Lewis and Clark saw no real significance in any of their encounters with mere pests. By 1850 only 15 different species of fleas had been identified—including the ones hosted by dogs and cats—and by 1900 the roster still listed fewer than one hundred. During the last two decades of the 19th century, however, it was discovered that fleas had actually been the carriers, or vectors, of the bubonic plagues which for centuries had decimated human populations worldwide (except in the U.S. up to that time). That was more than sufficient to turn the flea into a worthwhile object of research and discovery, and by 1950 about 1,500 different species had been identified. By the beginning of the bicentennial observance of the Lewis and Clark expedition in 2003, nearly 2,500 varieties had acquired binomial identities, with some 325 of those (classified under 66 genera in seven families) found in the U.S. and Canada alone.^[12]“Historical Notes,” in Govnor Brinck-Lindroth and Frans G. A. M. Smit, The Fleas (Siphonaptera) of Fennoscandia and Denmark (Boston: Brill, 2007), p. 3. Ross H. Arnett, Jr., American … Continue reading

But his book quickly became a bestseller, so it is safe to assume that most readers back then merely smiled and nodded their agreement with the author’s own intense wonder and delight in every secret that his microscope had revealed.

A Reason to Jump

By the early 1700s Hooke’s Micrographia was long out of print, and as the English naturalist and microscopist Henry Baker (1698–1774) observed, “since a Desire of searching into the minute Wonders of Nature [has] become almost general,” and since nearly all of Hooke’s engravings were still in existence, a reprint was overdue. A new edition, retitled Micrographia restaurata (“restored”), appeared in 1745, based on 33 of Hooke’s 38 engravings. Baker himself revised and brought “up to date” Hooke’s old-fashioned, “verbose and disfused [sic] Way of Writing,” which he considered “tedious and distasteful.” For example, he reworded Hooke’s description of how a flea jumps, and then added a new theory as to why. The flea, he explained,

lives by sucking human Blood, or the Blood of other living Animals, which cannot be obtained without inflicting Wounds and causing Pain, which must necessarily produce Resentment, and a Desire of Revenge, it was absolutely requisite the little invader should have some ready Means of Escape; since every Meal must otherwise be paid for with its Life. As therefore it has no Wings, its Safety must be entirely owing to its Legs . . . whereby they commonly deliver the little Animal from the Danger of a Pursuit.^[13]Baker, Micrographia Restaurata (1780), 61.

Furthermore, he continued fancifully, “however pretty they may be in the Microscope, or for these ingenious Purposes, they are certainly very troublesome Bedfellows, and especially to Women and Children, whose Blood they are particularly fond of.”^[14]Ibid., 63. This and the previous quotation are typical of Mr. Baker’s “many Entertaining and Instructive Discoveries and Observations in Natural History” which he promised in his own version of Hooke’s Preface. Although his rather entertaining theories were refreshingly free of religious overtones, they were still far from reflecting the rigorous discipline of the Enlightenment‘s new standards of scientific method, at least as far as the trivial flea was concerned. Nevertheless, Hooke’s inimitable, “curiously engraved” plates continued to reappear in print throughout the 19th and 20th centuries, including scaled-down versions in paperback, and facsimiles of the several editions on CD-ROM and, most recently, full-scale editions on the World Wide Web.

In his paraphrase of the captain’s journals as of 26 December 1805 concerning the flea problem, Nicholas Biddle sympathetically summarized their effect on the natives along the lower Columbia. “These animals . . . are so numerous that they are almost a calamity to the Indians of this country.”^[16]History of the Expedition under the Command of Captains Lewis and Clark, Prepared for the press by Paul Allen, Esquire [Edited by Nicholas Biddle.] 2 vols. (Philadelphia: Bradford and Inskeep, 1814), … Continue reading Later, however, he referred to the nettlesome insect in a more kindly manner—as a “sagacious” animal.

Noah Webster defined the noun sagacity in 1806 as “quick of scent or thought,” which reflects the fact that it was then most commonly used in reference to certain domestic animals, such as Lewis’s Newfoundland dogs Seaman, when their natural intelligence seemed to resonate with, or perhaps even anticipate, that of humans. Even Indians were duly impressed by Lewis’s dog, Seaman. Of course, the diminutive size and the now uncivil reputation of the flea makes that conclusion absurd. Maybe Biddle had in mind the popularity of the “flea circus” in England (but not in the Colonies!) beginning in the 16th century,^[17]Brendan Lehane, The Compleat Flea, (London, John Murray, 1969), 56–64. so we may as well overlook the subject.

However, although fleas obviously do not have eyes, ears, noses, or brains like dogs or humans, nor do they have skeletal bones to support their muscles and organs, they most certainly can “see,” “hear,” “smell,” and “feel.” So, fleas can indeed be “sagacious animals,” although only in a sense proportional to their size.

That is to say, the ranges of their options are extremely narrow. For example, a flea has a sensory structure on the back of the last abdominal segment called a sensillum, through which it can sense the approach of enemies or hosts from changes in air currents and vibrations that are transmitted down hair shafts.^[18]Alan Gunn and Sarah Jane Pitt, Parasitology: An Integrated Approach (Chichester, West Sussex: John Wiley & Sons, 2012), 160. Some miss the mark, but others land firmly on the moving hosts at ankle height or a little above, and swiftly scramble upward away from the glaring sunlight, expecting to plunge into the deep shadows of fur, or feathers, or else—in the case of the Corps of Discovery—the mens’ buckskin clothing.

Offspring

In a flea’s instant, the females will deftly inject their siphons into the new host’s flesh and begin at once to drink. Within 48 hours, each well-nourished mother-to-be will lay a clutch of between 3 and 8 sticky white eggs somewhere in her host’s nest, which, unless destroyed by the hands of the host, within another few hours will hatch into larvae (pronounced either LAHR-vee or LAHRV-eye). Each of the larvae will grow through six instars (Latin for “forms” or “figures,” i.e. stages or molts;) before leaving their cocoons to change into imagoes (im-AH-goz), each of which will endure an identical, eons-old, 30-to-45-day cycle of its own.

It is impossible to identify the flea species that held the attention of the Corps of Discovery for most of the six months they spent on the banks of the Lower Columbia River and adjacent seacoasts. And even if the captains had been able to call them by any other name, it would hardly have affected the expedition’s history. The captains—and no doubt all the rest of the party, including Sacagawea and Seaman—recognized them immediately and took appropriate steps to deal with them. There was no need for anyone to get down on hands and knees with a “burning glass”—magnifying glasses from the Corps’ presents for Indians—and figure out what to call those pests. And no one needed to be assured that these little animals would abandon the expeditions’ bodies as soon as they arose in the morning, and that the places to begin exterminating them were the dark folds and crevices of their bunks. The captains simply issued an order concerning the importance of keeping their own huts, beds and selves clean, and compelling each man to catch and kill his own fleas.

Fleas or Lice?

In the fair copy of his journal entry for 26 October 1805, Clark reiterated the facts concerning the onset of their new curse three days previously: “The Flees—he underlined the word for emphasis, as if someone in the company had challenged him about their true identity. “The Flees,” he insisted, “which the party got on them at the upper & great falls, are very troublesom and dificuelt to get rid of,” etc. Two hundred years later Professor Gary Moulton, editor of the University of Nebraska Press’s new edition of the journals, might have been siding with Clark’s anonymous disputant when he expressed a still common error in his behalf: “It seems more likely,” editor Moulton wrote, “that the ‘flees’ are lice, since fleas do not attach themselves to hosts for any length of time.”^[19]Journals, 5:344n. His citation refers to the 7th edition of Entomology in Human and Animal Health, by Robert F. Harwood and Maurice T. James.^[20](New York: Macmillan, 1979), pages 129-41. The twelve pages are devoted to two kinds of lice, “sucking” (pp. 129-38) and “chewing” (pp. 138-41). But neither that passage nor their discussion of fleas (pp. 319-24), contains any direct comparisons between the two species, except regarding their respective anatomies (p. 322). “No part of the external anatomy of an adult flea,” Harwood and James insist, “could possibly be mistaken for that of any other insect. The head, the mouth parts, the thorax, the legs, the abdomen, the external genitalia, all present features that are not elsewhere duplicated among the hexapods [six-legged arthropods].”^[21]This topic has been included merely to illustrate the major observable differences between lice (Pediculus humanus L.) and the flea, relying on Robert Hooke’s enlarged microscope images of … Continue reading

As Harwood and James have pointed out, consistently warm temperatures are critical for the survival of louse populations: “The optimum for the adult body louse is approximately the temperature of the normal human body. A rise of 4 to 5 degrees is fatal to them within a few hours. Temperatures below the optimum are much less critical, although prolonged exposure to 20° C [68° F] or lower may result in death.”^[22]Harwood & James, 132. Therefore, since the average winter temperature in the vicinity of nearby Astoria, Oregon, is somewhere in the 40s Fahrenheit, the likelihood of lice prevailing there at all in that season is only marginal.

Fleas, however, are hit-and-run parasites. As soon as the host leaves its bed, most fleas will leap off their hosts’ bodies and hide for the day in the seams and creases of the bedding. The captains must have recognized that conduct from ample experiences, for as Clark informs us, as soon as they settled into their huts at Fort Clatsop, it became necessary to assign an enlisted man daily to clear the captains’ beds of fleas. Body lice, however, take up permanent residence in or on the host’s clothing, leaving only for blood meals on adjacent flesh that may last from a few hours to several days. Meanwhile, the host may be unaware of a louse’s presence until its engorged abdomen comes to his attention during a casual scratching of a mild itch.

Flea Odyssey in Eight Vignettes

Vignette 1: Long Time Ago

Some paleontologists believe that the earliest ancestors of today’s flea may have appeared—little by little, no doubt—in the Devonian period of the Paleozoic Era, between roughly 419 and 359 million years ago (Mya). Fossilized specimens from the Devonian would happily confirm their hypotheses, but the oldest known fossil remains of the species date from the post-dinosaurian period known as the Paleogene, which lasted from 66 to 23 Mya. To the benefit of the flea—as if it were part of a master plan—the Paleogene witnessed the evolution of many species of small fur-bearing mammals, including numerous rodents that could serve as hosts to the little ectoparasites, and whose nests and bedding sites would have provided their offspring convenient cover to protect them from predators.^[23]E. D. Lukashevich and M. B. Mostovski, “Hematophagous [blood-sucking] Insects in the Fossil Record,” Paleontological of Journal, vol. 37, no. 2 (2003), 153-161. Translated from the … Continue reading Diaphanous images of a few fleas have been found in amber stone, which is the fossilized resin of certain now-extinct tree species that are native to the rim of the Baltic Sea (44 Mya), the eastern Mediterranean Levant, and the mountains of the Dominican Republic (25 Mya), but there are not enough to provide answers to some of the flea’s evolutionary history.^[24]Robert F. Harwood and Maurice T. James, Entomology in Human and Animal Health, 7th ed. (New York: Macmillan, 1979), 319. For example, it is highly unlikely that the morphology of the flea was static for all those millions of years since it’s principal hosts must have changed theirs, but how and when, and especially why, remain securely hidden—at least for the present.

Regarding the ancient biography of the flea from another angle, the order survived on rodents, a few birds, and perhaps a few reptiles for almost all of that hypothetical 359 Mya sojourn before the first tribes of Homo sapiens evolved, bringing with them languages in which to complain about them. Next, it may have been a mere 200,000 years ago when Homo neandethalensis, among others, began to wear clothes,^[25]Bent Sørensen, “Energy use by Eem Neanderthals,” Journal of Archaeological Science, Vol. 36, Issue 10 (October 2009), 2203. which was a real boon to insects that preferred human blood, because the encasement created protection from daytime heat for traveling fleas, a platform from which to enjoy nighttime bloodsucking, and dry beds to protect them from rain as well as predators during the day.

Somehow they sensed what they had to do: find a host from which a female flea could sip enough protein-rich blood to enable her to produce 3 to 8 eggs, which within 48 hours would yield an equal number of larvae (worms), which in turn would prevail for 9 to 15 days, then segue into pupae for an indeterminate period, and finally emerge into adulthood. On average, a majority of fleas require from 30 to 75 days for a complete life cycle, although within the past hundred years entomologists have found many fleas with much longer or shorter lifespans.

On the whole, a flea’s life is a chancy venture.

Vignette 2: Fade to the Biblical Age

Some linguists maintain that the beginning of verbal communication between you and me was coincident with the emergence of our own early species, Homo sapiens. Wouldn’t it be interesting to learn how our very first ancestors coped with fleas verbally—along with other universal nuisances such as mosquitoes. The answer is out of our reach, of course, but . . . would it be printable?

In the Old Testament the flea was a symbol of humility and insignificance. David (c. 1040–c. 970 BCE), a young shepherd who was destined to become King of Israel, was feared and envied by his predecessor, King Saul. With assassination in mind, Saul pursued David with an army of three thousand men, intent upon celebrating his demise along with his few friends. When they met, the youth defended himself against Saul’s slow-witted display of might by pointing out that he was “poor and insignificant,” and ridiculed Saul’s audacity with the image of himself as no more powerful than a flea: What was the king of Israel after? The dog is dead! The fleas are gone! In a later confrontation he taunted Saul again: “The King of Israel has come out to seek a single flea as if he were hunting partridges in the mountains?” Saul would have known that partridges were upland Eurasian game birds which are found only in open fields and prairies.^[26]First Book of Samuel, Chapter 24, verse 15, and Chapter 26, verse 20. New American Bible, St. Joseph Edition, Revised. See also Warren Wiersbe, The Bible Exposition Commentary

Vignette 3: Moses’ and Aristotle’s ‘Dusty’ Theory

The deep and durable Biblical doctrine that God created humankind out of dust sidestepped the logical paradox that life can only proceed from life. Thus the assumption that the lowest forms of life, which we call insects—the word refers to the segmentation of the diminutive species’ bodies—can only have emerged from dust or worse, was confirmed by the earliest Greek philosophers and defined by Aristotle, on the premises that the insect has no heart, no blood, no brain, and apparently no reproductive organs. It explains the story of the Third Plague in the Captivity, recounted in Exodus 8:16-19. The Lord directs Moses to command Aaron: “Stretch out your staff and strike the dust of the earth, that it may become gnats [including fleas] through all the land of Egypt.”

For more than two thousand years the doctrines of the proto-scientist Aristotle (384-322 BCE) concerning animal life, formed the bases for an unending variety of tropes on the Greek philosopher’s Ladder of Life. “So with animals,” he had written, “some spring from parent animals according to their kind, whilst others grow spontaneously and not from kindred stock; and of these instances of spontaneous generation some come from putrefying earth or vegetable matter, as is the case with a number of insects.” Such as the flea.^[27]Aristotle, The History of Animals, (written ca. 350 BCE) translated by D’Arcy Wentworth Thompson. Book V, Part 1. The Internet Classics Archive (c. 350 BCE) … Continue reading

Vignette 4: How Narrow is the Pipe Whereby it Sucketh!

Aurelius Augustinus Hipponensis (354–430 CE), properly known as Augustine, Bishop of Hippo^[28]An ancient city on the north coast of Africa a few miles west of Tunis., but longer and more widely as St. Augustine. His works are still widely read and admired for his profoundly insightful, verse-by-verse meditations on each of the 150 Psalms, which he originally prepared and delivered orally to his catechumens. Fortunately, they were written down by teams of scribes for publication. In all of his writings, his literary style was that of the common man, embellished with thoughtful re-phrasings and topical alternatives to the original Hebrew transcriptions, that would seize the lagging attention of his pupils, and sear the truths into their memories.

For example, in Psalm 148 a reverent regard for all God’s creatures is preached, regardless of their positive or negative values to humans. Verse 10 of the 14 verses in Psalm 148, for example, lauded “Animals wild and tame, creatures that crawl and birds that fly.” No particular species were named in the original version of the Psalm, so Augustine arbitrarily chose the flea and the mosquito to represent the smallest and least imposing of the Divine Creator’s works. They were certainly among the most ubiquitous living creations of all time, each being—to paraphrase a modern pedagogical cliché—a “teachable species.”

The homilist urged his young pupils to think about this:^[29]A homily is “a practical discourse with a view to the spiritual edification of the hearers, rather than for the development of a doctrine or theme.” OED. “Who has arranged the limbs of a flea and a gnat [mosquito] that they should have their proper order, life, motion? . . . If you consider . . . that animation of life whereby it moves; how does it shun death, love life, seek pleasures, avoid pain, exert various senses, vigorously use movements suitable to itself!”

Then, abruptly, came his own tagline: See, he said, “how narrow is the pipe whereby it sucketh!” Here was knowledge, truth of Divine Creation, forever hidden from unassisted sight. Surely that would have jerked the drowsiest of his pupils to attention. Few if any of them could ever have imagined, much less distinguished, those “sucking parts,” yet no one could ignore the fact that they were what produced that persistently irritating, swollen little red spot on one’s skin, with a darker hole at its center—not a bite at all, but a puncture. It sounds as if their homilist had seen those parts himself.

But how? The microscope was still more than a thousand years in the future. But if the prelate had thoroughly examined the flea’s anatomy, it could have been with a simple magnifying glass of the type often used by craftsmen such as engravers, A sample hand lens was found in a shop at Pompeii that was buried deeply beneath volcanic ash and pumice by the eruption of Mount Vesuvius in the year 79 CE. Also, it was sometimes used to light fires. (Meriwether Lewis took along eight dozen “burning glasses” to bestow as gifts upon natives the Corps of Discovery met along the expedition’s route.)

Simple magnifying glasses were sometimes used to locate fleas on one’s own body before they began feeding. Indeed, early in the 17th century they were commercially sold as vitres pulicaria—”flea glasses.” The only other way Augustine could have learned of the smallest organ on the smallest insect would have been to rely on a myopic or extremely near-sighted acquaintance to make a visual examination in his behalf.

During the Renaissance (1450–1600), Baroque (1600–1750), and Romantic (1750–1900) Eras, fleas were often treated as literary or artistic pets by painters, poets and essayists, who used the predictably energetic insects to highlight social, moral, or erotic themes—none of which are present in this depiction.

A painterly style known as chiaroscuro (KEE-ah-ro SKOO-ro; Italian for “light–dark”) used a single light source to subtly create deep shadows to subtly frame the subject’s space on the canvas. George de La Tour of Lorraine, France, was the acknowledged master of the technique. In the above painting it tells us that this young woman, with her hair still neatly tucked beneath a linen coif or nightcap, has been aroused from sleep by at least one flea that sought to sip a drop of her blood. It is a distraction that she, like everyone else on earth, simply has to put up with.

Her fists—unbecoming a pretty woman—are poised in flea-crushing curls with thumb-nails opposed, ready to squeeze the unwelcome intruder between them. She has doused one nail with a deep drop of spittle to impede the flea’s escape—a flea can’t swim in anything. Her impassive expression betrays no anger, no fear, no moral repugnance. The otherwise voiceless Siphonaptera will die with a whispered “click.”

With its muscular torso and legs, faintly tattooed shoulders and arms, a slightly oversized head with small sharp horns and a tongue shaped like a siphon, the ghost, poised for a cosmic leap, looks out upon nearby stars at the fringe of the galaxy that hosts our solar system. The American art historian Hope Werness has suggested that Blake’s inner vision of his subject may have been inspired by Robert Hooke’s enlargement of his microscopic image (See figure in A Closer Look).^[30]Hope D. Werness, The Continuum Encyclopedia of Animal Symbolism in World Art (London: Continuum International Publishing Group Ltd., 2006), 180.

The artist was said to have exclaimed to an acquaintance at the moment he began work on his vision: “There he comes! his eager tongue whisking out of his mouth, a cup in his hand to hold blood, and covered with a scaly skin of gold and green.” Thus does Blake’s image become a visual metaphor for Hooke’s monstrous depiction of the tiny but well-built parasite. As Blake once explained to a young artist, “you have only to work up imagination to the state of vision and the thing is done.”

William Blake was a seminal force in the rise of English era of Romanticism, which overlapped in the young U.S. with the Federalist and Post-Federalist eras. He was the senior by about fifteen years of the Lake Country poets, William Wordsworth, Samuel Taylor Coleridge, and Robert Southey. Coincidentally, Meriwether Lewis (1774–1809) and William Clark (1770-1838) and all their expeditionary men were contemporaries of all those famous British Romanticists, although their world-views and their literary styles were in no way like those of Blake and his friends.

Vignette 7: Some say ‘not my problem’

Dateline Waterbury, Connecticut, 11 August 2011

Four fighters were dispatched to an abandoned frame house that was often occupied by transients, and that appeared to be a fire hazard. They were to map a response strategy in the event it should catch fire in the future. It wasn’t long before each of the firefighters began to itch, and scratch, and they were driven out of the house by the myriad fleas that had quickly covered their bodies—thousands of them, they declared. Think of it. Their turnout gear could protect them from the heat of a fire up to 500° Fahrenheit, but it was not designed to keep out fleas. On the contrary. . . .

As quickly as they could, they raced to the nearest hospital where, after they stripped down and brushed off all the fleas they could, they were vigorously scrubbed down, and treated for their numerous flea punctures. Meanwhile, their gear was being washed inside and out at a high temperature, and the fire truck was duly fumigated before being returned to service. The four firefighters had to go back to the hospital the next day to be tested for flea-borne infections such as bubonic plague.

Now, whatever became of that flea-infested house?

Twenty million years ago. That is when—give or take a few millennia—this particular flea succumbed to the consequences of its own misstep. It somehow fell into a puddle of malleable resin which was exuded from a now extinct tropical tree bearing the generic name Hymenæ (him-men-EYE-uh), and the species epithet protera, “a poker”—a flea—by Carl Linnæus in 1753.^[31]The generic name is a poetic evocation of the Greek god of marriage ceremonies, Hymenaios, whom nature appears to have deliberately symbolized by paired, mirrored leaves connected by short petioles … Continue reading Subject to the aging processes of oxidation and polymerization over a period of 3–4 million years, the resin became a semi-fossilized substance called copal, and eventually was hardened into the gemstone we call amber.^[32]George O. Poiner, Life in Amber (Stanford, California: Stanford University Press, 1992), 6.

This image is especially remarkable for several reasons: First, very few fleas and ticks have been found in amber because they generally cling to their fur-bearing or feathered hosts, which are too large for the average capacity of the medium.^[33]The average weight of raw amber droplets is 1.76–3.5 oz (50–100 grams). The largest natural amber on record was found in 2014 in west Sumatra, a province of Indonesia. It weighs 105 lb (47.6 kg), … Continue reading Second, the biological inclusion is complete enough for an experienced paleo entomologist to identify its species, which in this case is one that went extinct millions of years ago. It was discovered in 1995 by the renowned paleo entomologist George O. Poinar, of Oregon State University, who gave it its one and only formal name, Atoposyllus cionus.^[34]Both parts were derived from Greek words. The generic name is a combination of atopos, “strange,” and posyllo, “flea,” (AT-oh-poh-SIL-loh). The specific epithet, expanded from … Continue reading Third and finally, this is the first specimen of amber found to contain a flea which in turn bears—at the distal end of its mouth parts—droplets of dried bacteria believed to be related to the hideous Black Death microbe, Yersinia pestis.^[35]“Bacteria in ancient flea may be ancestor of the Black Death,” News and Research Communications, Oregon State University, Corvallis, Oregon, 28 September 2015.

The drop of amber that encased this biological inclusion was found in a shallow mine in rocky soil atop a mountain of the Greater Antilles archipelago in the Dominican Republic, which occupies the eastern two-thirds of the island of Hispaniola, between the Gulf of Mexico and the Atlantic Ocean.^[36]The western third of Hispaniola is occupied by the nation of Haiti.

Bear in mind that this flea, dead or alive, was only about 3 mm in length.