Innumerable Insects

by Michael S. Engel

  The title page of a 1758 edition of Carl Linnaeus’s Systema Naturae (1735), wherein he stabilized the method by which we hierarchically classify the world’s species.

  Linnaean Hierarchical Classification

  The classification of the domesticated silk moth, Bombyx mori, is shown below, using the canonical ranks of the Linnaean system, with each group subordinate to the one above it.

  ENTOMOLOGY IN ANTIQUITY

  Entomological observation extends deep into antiquity, and well before any written record. Our mythologies and religions are rife with references to insects, and tales of their lives filter into proverbs and parables. We are all familiar with Aesop’s fable of the ant and the grasshopper, and the story of the plagues of biting insects and locusts brought down upon Egypt as related in Exodus. The earliest surviving account of an attempt to arrange, classify, and understand insects is that of Aristotle (384–322 BCE), the famed Greek scholar who mentored a young Alexander the Great, set forth the principles of formal logic, and is widely credited as the father of many lines of philosophical inquiry. Aristotle’s Historia animalium, along with other works of antiquity, rightly recognized many of the groups we still know today, distinguishing bees from wasps, butterflies from moths, locusts from crickets. Although modified through the ages, Aristotle’s writings would remain influential in one form or another for the next two thousand years. After him, entomological endeavors continued, but writers focused their discussions on strictly practical matters, covering only the most obvious species as they related to humans, or sought insects as moral allegories.

  Dioscorides (40–90 CE), a Greek botanist and physician from Cilicia (modern-day Turkey) who worked in Rome during the rule of the infamous Nero (r. 54–68 CE), wrote an interesting pharmacological text, outlining the use of insects to cure numerous ills. Individuals suffering from quartan ague—recurrent fevers possibly caused by influenza or malaria—were treated by mixing seven bed bugs and beans with their food, while earaches could be eliminated with a tincture of ground cockroaches and oil. The contemporaneous Roman naval commander and naturalist, Pliny the Elder (23–79 CE)—who famously perished in Pompeii during the eruption of Mount Vesuvius—wrote an encyclopedia called the Naturalis historia, which, like Aristotle’s volumes, would stand as one of the definitive sources for all things natural for more than a millennium. Pliny’s arrangement of insects was effectively that of Aristotle’s, but the individual biological information on each species did differ considerably at times. Roman authors, ever so practical as they were, wrote more extensively on the agricultural impact of insects, and Roman remedies for the control of pests may be found amid writings on farming and viticulture. Nonetheless, humanity had yet to appreciate the full diversity of the insects around them or the fact that conspicuousness does not always equate with importance.

  A snapshot of aquatic insect diversity amid their environs at different stages of life. Across the top, the broad-bodied darter dragonfly (Libellula depressa): left, as a naiad shedding its skin while suspended from a blade of water grass; at right, the adult in flight. In the center, an adult mayfly, far left; a ruddy darter dragonfly (Sympetrum sanguineum), left; a beautiful blue demoiselle damselfly (Calopteryx virgo), right; the large caddisfly Phryganea grandis, bottom, flying over a pond’s surface. Beneath the water are mayfly and dragonfly naiads (left) and caddisfly larvae cases (right). From Musée entomologique illustré: histoire naturelle iconographique des insects (1876).

  The splendid variety of insect life from the frontispiece of John O. Westwood’s textbook An Introduction to the Modern Classification of Insects (1840), illustrated by the author. Clockwise from top left: northern dune tiger beetle (Cicindela hybrida), eulophine parasitoid wasp (Dicladocerus westwoodii ), scarab beetle (Anomala donovani ), snowflea (Boreus hyemalis), ancient river water bug (Aphelocheirus aestivalis), bee fly (Phthiria fulva), twisted-wing parasite (Stylops aterrimus), diapriid wasp (Platymischus dilatatus), and ensign scale insect (Orthezia urticae).

  Entomology, and in fact virtually all scholarly endeavors in Europe, suffered greatly when the Western Roman Empire came to a crashing end in the late fifth century. Scholastic endeavors retreated to monasteries and lost the broad support once enjoyed under the imperial structure of Roman society. Monks and scribes did what they could to copy existing elements of knowledge, but owing to a focus on revealed truth over empiricism, mystical interpretations were growingly pervasive. Perhaps the most influential and enduring entomological work coming out of the latter phase of imperial disintegration was the Etymologiae of Isidore of Seville (ca. 560–636 CE). Isidore’s Etymologiae was an encyclopedic tome and therefore covered insects in his chapter on animals, but his take, characteristic of the time and indicated by the title, was to use the derivation of the names themselves as the explanation of an insect’s biology. The book was hugely influential, and it has been estimated that it was one of the most copied texts in late antiquity.

  Isidore classified his insects in disparate sections. De verminibus (vermin) included beetles, silkworms, termites, and lice, while De minutis volatibus (tiny flying animals) covered bees, roaches, butterflies, cicadas, locusts, and flies. The knowledge conveyed was riddled with errors, with notions of spontaneous generation as a common recourse. For example, “The hornet is named from cabo, that is, from the packhorse, because it is created from them” and “Bibiones drosophilae [a name Isidore gave to what were perhaps fruit flies] are creatures that are generated in wine.” Such insights could be found alongside the practical biology of basilisks—mythical crested serpents—and the belief that birds are born twice during their life. Many medieval writers continued along similar lines, although with each century came more departures from the traditions of antiquity. As in many things, however, the Renaissance brought a great flourishing in entomology.

  RENAISSANCE CLASSIFICATION AND INSECTS

  The first book dedicated strictly to insects, and particularly their classification, was De Animalibus Insectis Libri Septem (On Insects, Seven Books) (1602) by Ulisse Aldrovandi (1522–1605), a professor of natural science at the University of Bologna (see pages 20-21). Aldrovandi provided the first dichotomous key for the determination of insect groups, configuring the arrangement as he saw it graphically and in an iconography that, to the modern viewer, resembles a depiction of evolutionary relationships.

  Although it was only meant to reflect a dichotomous means of identifying and organizing information about insects and related invertebrates, this hierarchical classification by Ulisse Aldrovandi (from De Animalibus Insectis Libri Septem [1638 edition, 1602]) was prescient and in several respects accurately reflects evolutionary relationships.

  While he most certainly did not operate with a concept of evolution in mind, several of his pairings would be considered accurate by today’s analytical methods, attesting to Aldrovandi’s skill as an observer. His book was made all the more accessible by the numerous woodcuts. For each species placed in his system, he provided whatever biological data could be obtained either through direct observation or through a comprehensive compilation of all prior literature, some of which had been less than thoroughly vetted before being repeated. The English doctor Thomas Moffet (1553–1604) made a similar attempt at compiling entomological knowledge. Moffet’s Insectorum sive Minimorum Animalium Theatrum (The Theater of Insects, or Smaller Animals) (1634) was far less accurate or comprehensive, although some of the woodcuts are remarkable for their accuracy and were improvements over those of Aldrovandi, while others were simply unfortunate.

  The title page of Thomas Moffet’s Insectorum sive Minimorum Animalium Theatrum (1634), which summarized the contributions of many scholars and attempted to classify and describe the biology of insects and other arthropods then known. The work was prohibitively expensive to publish at the time and only appeared posthumously; his original illustrations were replaced with the fine woodcuts for which the book is known.

  Woodcuts of various dragonflies and damselflies
(order Odonata) from Moffet’s Insectorum.

  OPTICS AND INSECTS

  Neither Ulisse Aldrovandi nor Thomas Moffet had the advantage of examining their subjects with the aid of a microscope. Around the turn of the century, perhaps in 1599, the first optical microscope was invented in Middelburg, in the Dutch province of Zeeland by either Zacharias Janssen (1585–ca. 1632) or Cornelis Drebbel (1572–1633)—although who should rightly hold credit is controversial. As the world of insects is often beyond the limited reach of our eyes, this revolution in optics opened new vistas into entomological minutiae. While Antonie van Leeuwenhoek (1632–1723) is famed for being the first to publish illustrations of microorganisms using the new technological advances, he was not the first to publish observations made with a microscope. In 1609, Galileo Galilei (1564–1642) developed his own simple microscope, and by 1611 he had been recruited into a relatively new scientific society, the famous Accademia dei Lincei, founded in Rome by naturalist and scientist Frederico A. Cesi (1585–1630). The Lincei published some of Galileo’s early astronomical observations, including his treatise on scientific methodology, Il Saggiatore (The Assayer) (1623), and would later help defend him against the Church during his inquisition.

  Using Galileo’s microscope, Cesi and fellow Lincean Francesco Stelluti (1577–1652), a mathematician and doctor, studied and illustrated three bees, the famous triumvirate of bees from the Barberini family’s coat of arms. The detailed images of the bees and their anatomy were printed as a broadsheet in 1625, titled as Melissographia, and presented as a Christmas gift to Pope Urban VIII (1568–1644), born Maffeo Barberini, from the Lincei as a symbol of perpetuae devotionis (perpetual devotion). These were the first printed images of organisms as viewed through a microscope, and quite appropriately, they were of an insect.

  Cesi began expanding upon this for a book, the Apiarium, but died in 1630. Stelluti further developed the anatomical study, and incorporated the Apiarium into his Persio tradotto in werso sciolto e dichiarato ([Works of Aulus] Persius [Flaccus] Translated into Light Verse and Annotated) (1630), a text on the satires of Perseus meant to obscure the scientific observations being published, as Urban VIII remained less than favorable toward such inquiry. Insects would remain a subject of great fascination to early microscopists, and many were featured in English polymath Robert Hooke’s (1635–1703) famous treatise, Micrographia (1665), prepared with a significantly improved instrument relative to that of the Linceans.

  The first images produced with the aid of a microscope, one developed by Galileo, were a triumvirate of honey bees (Apis mellifera). Francisco Stelluti illustrated a worker bee from (from top left clockwise) underneath, the side, and the top, as well as finer anatomical details of the legs (bottom left), mouthparts and sting (bottom right), head (center right), and antenna (top center). From Stelluti’s Persio tradotto in verso sciolto e dichiarato da Francesco Stelluti (1630). The illustration was originally printed in 1625 in a broadsheet titled Melissographia, and presented to Pope Urban VIII as a Christmas gift.

  The title page of John Ray’s Historia Insectorum (1710), a work that laid out observations on the biology of numerous insect species and greatly influenced the classificatory efforts of scholars who followed Ray, such as Linnaeus.

  THE POPE’S DRAGON-SLAYER

  Ulisse Aldrovandi was born into a noble family in Bologna, then part of the Papal States. His parents named him after Odysseus (Ulixes being the Latin variation of that name), one of Homer’s heroes from the Odyssey and Iliad, while they named his brother for Achilles. Aldrovandi was inspired by the burgeoning sciences and humanities that were developing dramatically in sixteenth-century Italy. He studied logic, philosophy, mathematics, and law at the University of Bologna—the first university in Europe, founded in 1088—and completed a degree in medicine and philosophy in 1553. The following year he began teaching logic and philosophy, but he was more driven toward natural history. He began developing a collection of specimens and instructing students in natural science, eventually becoming the university’s first professor of natural sciences, in 1561. Collecting obsessively, Aldrovandi developed an extensive “cabinet”—as collections were then known—of natural curiosities, and, in 1568, founded the city’s botanical garden, a public garden, that is still in operation today.

  Aldrovandi was never lacking in self-assurance, even boasting that he was the sixteenth century’s Aristotle, and perhaps not surprisingly, he often found himself at odds with others. For instance, in 1549 he was arrested for heresy, before being pardoned by Pope Julius III (1487–1555) in 1550. Then in 1575, Aldrovandi’s quarrels with doctors in Bologna resulted in his suspension from the university. His mother was a cousin of Pope Gregory XIII (1502–1585), who is remembered by the eponymous calendar, among other reforms, that he commissioned to replace the Julian system of dates. Despite Aldrovandi’s prior run-ins with the pontifical seat, Gregory intervened on his behalf in 1577 and he was allowed to resume his positions.

  Portrait of Aldrovandi from his Ornithologiae (1599).

  Title page of Aldrovandi’s De Animalibus Insectis Libri Septem, the first textbook dedicated exclusively to insects.

  Aldrovandi’s collection ultimately grew to become one of the largest assortments of natural objects of the sixteenth-century Renaissance. He wrote thousands of pages for an encyclopedic treatment of natural history, although most of his work was not published until after his death in 1605.

  While Aldrovandi did much to advance natural history as a science, he was a creature of his time and many medieval notions permeated his writings, particularly as evidenced in his Monstrorum Historia (The History of Monsters) (1642) and Serpentum, et Draconum Historiae (The History of Serpents and Dragons) (1640). In fact, Aldrovandi was considered the dragon expert of the day, such that when Gregory was made pope, Aldrovandi was called upon to inspect a purported dragon that had appeared in the countryside; he declared it a positive omen for the new pontiff.

  One work that did appear during his lifetime was his De Animalibus Insectis Libri Septem (On Insects, Seven Books) (1602), an encyclopedia of everything to do with insects. Aldrovandi did not restrict his writing to mere practical applications, but attempted to consider all insect diversity as he understood it. This was a departure from previous generations and the reason why many regard him as the founder of modern natural history. Aldrovandi’s book can be considered the first textbook of entomology, and it even includes a dichotomous arrangement for his classification, the iconography of which is strikingly similar to that of an evolutionary tree. While advocating empirical evidence, Aldrovandi was, however, susceptible to questionable observations and rather incredible leaps in logical reasoning. In support of the ancient belief that bees were generated from the carcasses of oxen, he purportedly opened five drones, discovering within each of them the tiny heads of oxen—clearly irrefutable support for the hypothesis. Fortunately, it would not be long before the mysteries of metamorphosis would be revealed to all.

  Aldrovandi’s woodcuts of crickets, katydids, and grasshoppers from De Animalibus.

  LATER CLASSIFICATION: SPECIES, HIERARCHY, AND EVOLUTION

  While numerous other tracts on insects were produced, one of the more transformative efforts at classifying entomological diversity was the posthumously published Historia Insectorum (1710), by John Ray (1627–1705). Ray was an English naturalist and theologian who expressed a particular interest in botany and entomology. Quite amazing for the time in which he lived, Ray is credited with providing the first biologically based concept for what constituted a “species.” In brief, Ray considered species to be all those individuals who derived from a common progenitor, a notion so modern in form and analogous to the biological species concept—which would not be codified until 1942—as to be astounding. This prescient and succinct definition of species is a virtual blueprint, if writ over a larger scale, for evolution itself.

  Ultimately, this lengthy tradition led to Linnaeus and his own revolution in biologi
cal classification. In fact, authors such as Moffet and Ray so influenced Linnaeus’s thinking that he adopted many of the names they had employed for particular groups or species of insects. Linnaeus, like the authors before him, did not conceive of the classifications of insects in terms of evolutionary descent, yet they were unknowingly identifying enduring patterns reflecting the underlying evolution that had occurred. The process and mechanism of evolution, whereby changes in populations of an ancestral species diverge to give rise to novel descendant species, produces a hierarchy as a natural byproduct. So, at its simplest, we find that all arthropod species have an external exoskeleton, all mandibulate arthropods have mandibles as their primary feeding appendages, all insects have six legs and three body sections, all butterflies and moths have scales on their wings, and so forth; each sharing the suite of particular traits with their most recent common ancestor and its many descendants.