Butterflies are the general favorites among the order Lepidoptera, and perhaps none are more iconic than the great birdwings, such as the Magellan birdwing of the Philippines (Troides magellanus). From Robert H. F. Rippon, Icones Ornithopterorum (1898–[1907]).
Dwarfing the caddisflies in number of species are the moths and butterflies; with approximately 157,000 species, they are by far the most diverse group of plant-feeding insects. Unlike caddisflies, the wings of moths and butterflies are covered with small scales, and it for this reason that Linnaeus named their order Lepidoptera (in Greek, lepidos means “scale”). Aside from their lovely, scaled wings, all butterflies and all but the most primitive moths, have a coiled proboscis that is used to drink fluids such as nectar, water, or the juice of rotting fruit. In one of the more exceptional departures, species of the Southeast Asian moth genus Calyptra have evolved to imbibe blood from mammals.
Moth and butterfly larvae are called caterpillars, and almost all caterpillars are herbivores. The caterpillars of many moths are major agricultural pests, such as the tomato and tobacco hornworms, which are both caterpillars of species of the hawkmoth genus Manduca. Others are household nuisances, such as the clothes moth, Tineola bisselliella. Some moths, however, are greatly prized. The silkworm moth, Bombyx mori, does not occur naturally but is a domesticated form of B. mandarina, feeding on mulberry and having been selectively bred by humans for almost five thousand years. The silken cocoons are harvested and carefully unspun to produce treasured textiles, and in antiquity the secrets of sericulture, or silk farming, were guarded by penalty of death. These moths have been so vital to our global heritage that the ancient trade routes across Asia are known as the Silk Road, although much more than just silk was exchanged.
Many moths are tiny and go unnoticed except when they flutter about our lights at night. Species like the Atlas moth, Attacus atlas, and luna moth, Actias luna, however, are large and colorful, the former reaching up to 10 inches (25.4 centimeters) in wingspan, and many moths are as beautifully patterned as the most ornate of butterflies.
Butterflies are nothing more than garish, day-flying moths, comprising about 18,800 species, and yet they are perhaps the most familiar and beloved of all insects. For millennia, they have been the passion of enthusiastic collectors and naturalists and the muses of countless artists, poets, and dreamers. People have expended fortunes to gather the largest and showiest species, and it is no surprise that so many eighteenth- and nineteenth-century monographs revolved around finely painted portrayals of butterflies, perhaps only surpassed by those of birds and flowers. In fact, the earliest entomological societies—perhaps one of the first of all zoological societies—was devoted to butterflies. The Aurelian Society (a precursor of the present-day Royal Entomological Society) was founded in London in the late seventeenth century. The name Aurelian is derived from aurelia, an old Latin term for a butterfly’s chrysalis (the hardened pupal skin), which was itself derived from aureus, meaning “golden,” in reference to the hue assumed by the chrysalis of some species shortly before the emergence of the butterfly. The ostentatious colors of butterflies are often warnings to predators, indicating some degree of toxicity should they be consumed. Not all is as it may seem, however, for deception evolved repeatedly, with color mimics frequently indicating to predators a degree of toxicity not truly present (see pages 177-179). For all their beauty and delicacy, the colors of butterflies are at times meant to mislead, a reality that would have offended the sensibilities of most eighteenth-century Aurelians!
Flying insects with complete metamorphosis achieve what the rest of us merely dream of—living two different lives, at least metaphorically. Swammerdam and Merian showed that these different lives were truly one, carefully observing what others were unable to see: larvae specialized for one set of conditions wiggling through water, scurrying over land, or burrowing through muck to later assume new skin, new habits, and a new identity as winged adults.
Detail of various parasites, from M. Olivier, Encyclopédie méthodique. Histoire naturelle. Insectes. (1811) (also see page 109).
“So, Nat’ralists observe, a Flea
Hath smaller Fleas that on him prey,
And these have smaller Fleas to bite ’em,
And so proceed ad infinitum.”
—Jonathan Swift On Poetry, “A Rhapsody,” 1733
Most insects do not bite or sting, and yet we tend to treat them all as pests or menaces. As a natural protective mechanism, humans remember traumatic events more intensely so that we become wary of the sources of those traumas in the future. This same protective focus applies to us both culturally and as a species, and it is therefore understandable that we might recoil from insects based on an ingrained response to past bites or stings, whether inflicted on ourselves, our societies, or our distant progenitors. It is true that certain insects can pose a danger by competing with us for food, bringing ruin upon our homes, or directly threatening our health—particularly should certain allergies exacerbate whatever toxins might be presented. Nonetheless, pests and parasites of humans, despite their prominence in our collective conscience, represent the tiniest fraction of the world’s insect species, and we should resist our innate urge to swat or revile them as a first response. Most insects go about their lives utterly ignored by us, doing us no harm and instead benefiting humanity in the various means by which they help our ecosystems function. That said, when insects do make themselves noxious and “bug” us, they are so very adept at doing so.
A copper engraving of a mosquito (perhaps Culex pipiens) prepared by Jan Swammerdam for his treatise on the natural history and development of insects, Historia Insectorum Generalis (1685 edition, 1669).
A variety of mosquitoes and their relatives. At center, the mosquitoes Anopheles maculipennis. Clockwise from top left, common house mosquito (Culex pipiens), another mosquito (Aedes cinereus), phantom midge (Chaoborus crystallinus), lake fly (Tanypus varius), biting midge (Serromyia femorata), and a chironomid midge (Chironomus plumosus). From Georges Cuvier, Le règne animal distribué d’après son organisation (1836–1849).
FLEAS AND LICE
Hans Zinsser (1878–1940), the American physician who isolated the typhus bacterium and developed a vaccine against it, rightly wrote in his book Rats, Lice, and History (1935): “Swords and lances, arrows, machine guns, and even high explosives have had far less power over the fates of the nations than the typhus louse, the plague flea, and the yellow-fever mosquito.” Typhus and bubonic plague alone have brought conquering armies to their knees, reduced cities to mass graves, and spread terror through civilizations more than any atrocity.
Fleas such as the house flea (Pulex irritans) can have a wide range of hosts, making it easy for them to transfer between species, such as from house pets to humans. From August Johann Rösel von Rosenhof, De natuurlyke historie der insecten (1764–1768).
By example, the Justinian plague, spread by rat fleas putatively from Egypt and Palestine, burst forth in Constantinople in 541 CE. Exacerbated by climatic shifts of the time, this severe form of bubonic plague ultimately left twenty-five million dead across Europe and the Levant, which is believed to be about 13 percent of the total human population at the time. A pandemic of proportional impact today would wipe out the current population of the United States three times over. Emperor Justinian I (r. 527–565), famed for the construction of the great Hagia Sofia cathedral, was himself beleaguered by the infection but was among the minority who survived. Unfortunately, Justinian’s legacy was so marred by the plague that his name was lent to that particular outbreak. Indeed, the great English historian Edward Gibbon (1737–1794) wrote in his History of the Decline and Fall of the Roman Empire (1776–1788) that Justinian’s reign “is disgraced by a visible decrease of the human species, which has never been repaired in some of the fairest countries of the globe.”
A human louse (Pediculus humanus) from Robert Hooke’s landmark Micrographia (1665), the first book to illustrate minute animals a
nd the details of plants as observed through various microscopic lenses. With the aid of his lenses, Hooke was the first to describe and name the cell, as well as the fine anatomical details of insect eyes and other structures.
A plethora of parasites: a pair of mating fleas (order Siphonaptera, top left) and crab and body lice (Pthirus pubis, bottom left, and Pediculus humanus, bottom right) flank various other parasitic arthropods, from beetles to ticks. From Olivier, Encyclopédie méthodique…. Insectes.
Another emperor, Napoléon, marched on Russia in 1812 with approximately six hundred thousand troops, but he retreated after a harsh winter, malnourishment, and lice ravaged his army with typhus. A mere month into his campaign, typhus had already taken over a tenth of his men, and many more would also succumb to the illness. Six months later, after decimation by unsuccessful battles, starvation, cold, and disease, they marched back into France, numbering only around thirty thousand.
Add to these afflictions malaria, dengue fever, yellow fever, leishmaniasis, sleeping sickness, Chagas disease, and myriad more, and there is every reason to be wary of disease-carrying insects. However, there is no insect species that itself causes disease; instead, certain insects are vectors that carry and transmit pathogenic bacteria, protozoans, and viruses.
Interestingly, in the case of epidemic typhus, the disease is as fatal to the lice as it is to us. The body louse, or Pediculus humanus humanus, is the species known to transmit Rickettsia prowazekii, the bacterium that causes typhus, to humans. (The louse does not transmit Rickettsia through its bite but instead through its feces, which get rubbed into the wound as the bitten person scratches.) A louse becomes infected with Rickettsia by feeding on a human already acutely afflicted by the disease, and then it may transmit the illnessto another individual before it perishes. The bacteria proliferate inside the louse’s gut, so much so that eventually the gut lining bursts and the louse dies. One might say that from the perspective of the louse, we are the disease-carrying agent bringing an infection to it.
KISSING BUGS, TSETSE FLIES, AND MOSQUITOES
Chagas disease is spread through a mode of transmission similar to epidemic typhus. The disease, which is widespread through the tropical Americas, is caused by the protozoan Trypanosoma cruzi. As with epidemic typhus, the protozoan is found in the feces of the insect vector, which in this case are certain species of “kissing” bugs of the subfamily Triatominae. In human habitations, the triatomines live in rafters or other peripheral locations, coming out at night to feed. The bugs defecate promptly after feeding, and it is through scratching that the parasites enter our bodies. Some historians believe Darwin, who suffered greatly throughout much of his adult life, was afflicted with Chagas disease, the result of a bite from a triatomine during his travels through Argentina on the voyage of the HMS Beagle.
Sleeping sickness, or African trypanosomiasis, is also caused by a species of the protozoan genus Trypanosoma, but it is injected into the bloodstream when tsetse flies feed upon us. Malaria is similarly brought on by a parasitic protozoan—the genus Plasmodium—transmitted by mosquitos of the genus Anopheles. The protozoan invades the salivary gland of the mosquito, and the parasite can then be transferred to us through the mosquito’s saliva when it bites us. Plague is caused by the bacterium Yersinia pestis, which infects rodents. In urban areas, rats are largely the carriers, but mice, squirrels, and even gerbils can be infected. The rodents are then fed upon by the Oriental rat flea, Xenopsylla cheopis, which can then transmit the bacteria to humans when rodents come into close proximity to people and share their fleas with us. During historical pandemics, climate-driven outbreaks in Asia—likely originating from wild gerbils—would sweep into Europe where transmission by rodents and fleas in the filthy confines of medieval cities led to disastrous results.
BED BUGS AND MAGGOTS
Not every individual louse or flea has the potential to do such harm, even if those species feed upon us. The bite of the average mosquito typically causes nothing more than an annoying, itchy welt, although some blood-feeding insects can cause pain through severe irritation or allergic responses. Bed bugs are a scourge that is making a considerable comeback in our cities, owing to increased resistance to greatly overused pesticides. There are less than one hundred species in the exclusively blood-feeding bug family that includes the common bed bug. Only three of those species feed on us, and of those three, only two are particularly troublesome. The rest of the family evolved to feed on bats, birds, or small mammals, and they pay us no heed. The common bed beg is Cimex lectularius, the species name taken from the Latin word for a bed or couch. Bed bugs are not known to be capable of spreading any disease agents; it is more their irritating bites and invasiveness that are of concern. So pervasive have these wingless Hemiptera been in our lives that we even wish our loved one’s a pleasant night’s sleep with “good night, sleep tight, don’t let the bed bugs bite!” The original hosts of bed bugs were likely bats, and C. lectularius may still be found on bats even today, as well as on chickens or other domesticated animals.
It is believed that bed bugs first came into regular contact with humans who shared caves with bats in the Middle East, and they spread with us as we advanced our civilizations. Bed bugs do not live entirely on their hosts; they only venture onto the body during the night in order to feed, retreating during the day to peripheral areas of the roost, nest, or, in our case, bedroom to rest and reproduce. Bed bugs inspired some of the first exterminator companies, which appeared in London in the 1650s. In 1730, British exterminator John Southall published a pamphlet on bed bugs, titled A Treatise of Buggs, in which he more thoroughly outlined their biology than had been done previously. Southall offered for sale his services in administering to furniture and homes a mysterious concoction, his “nonpareil liquor,” said to be the most effective means of exterminating the vermin and taught to him by an aged African during his 1727 visit to Jamaica. Not everyone was pleased with his keeping hush the formula, and a J. Cook penned a letter to the London Magazine chastising him for doing so.
The common bed bug (Cimex lectularius) first became associated with humans when we still resided in caves of what is now the Middle East, and they have subsequently spread with us throughout the world. Detail from Cuvier, Le règne animal…
The frontispiece and title page of John Southall’s A Treatise of Buggs (1730), a work in which he advertised his “nonpareil liquor”—a natural remedy for bed bugs of which he learned while traveling in Jamaica. The frontispiece shows the developmental stages of the common bed bug (Cimex lectularius).
OF LICE AND MEN
It is little wonder that the most beautiful of illustrated works from the nineteenth century rarely figured ectoparasites (parasites that live on the exterior of their hosts) of humans, such as fleas or lice. How much pleasure might there be in viewing colorful displays of animals so wretchedly reviled? And yet, one of the more remarkable monographs of the period was specifically centered on lice. Henry Denny (1803–1871) was a British entomologist who was widely considered a leading authority on parasites. In 1825, Denny was appointed as the first curator for the Leeds Literary and Philosophical Society, which established the Leeds City Museum. In 1842, he published his Monographia Anoplurorum Britannae ( A Monograph on the British Anoplura), a work devoted to the Anoplura, the group of sucking lice that includes the three species so pestiferous to humans. Worldwide there are about 550 species of Anoplura, the vast majority of which live on a wide range of mammals—from aardvarks and elephants to lemurs and even seals.
Denny began the project in 1827 and spent fifteen years working during his leisure hours, often being rebuked by others for undertaking a work on a group, as he wrote in the preface to his monograph, “whose very name was sufficient to create feelings of disgust.” He did everything himself, including preparation of the many fine and accurate anatomical illustrations, figuring all the species, and summarizing everything known about them at the time. It is difficult to conceive of lice making f
or gorgeous figures, and yet Denny’s “louse-y” monograph did just that. Denny worked in an era prior to an understanding of evolutionary processes or the role that human lice play in spreading disease-causing microorganisms, and this lead to some rather quaint perspectives on the origins and purpose of such parasites in nature. Denny wrote in the preface,
It is a testament to Henry Denny’s illustrative powers that lice, so reviled, should be rendered sublime. The ungulate sucking lice (family Haematopinidae) featured here—from Denny’s Monographia Anoplurorum Britanniæ (1842)—feed on many of our domesticated animals.
As regards the period when Parasitic animals were first created, I shall not offer an opinion, the subject being one of those speculative theories which it is impossible to reduce to a demonstration. Though my venerable and esteemed friend, the father of British Entomologists, the Rev. Dr. Kirby, has conjectured, that Parasitic Insects infesting the human race, were not called into existence until after the fall of Adam. “Can we,” (he says), “believe that man in his pristine state of glory, and beauty, and dignity, could be the receptacle and prey of these unclean and disgusting creatures?”
In reality, lice are quite ancient. A magnificently preserved bird louse was discovered in shale from Germany that is approximately fifty million years old. Lice species were infesting mammals for eons prior to humankind, and they most certainly plagued our many hominid ancestors long before our species appeared. Denny also noted that,
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