Innumerable Insects
Page 16
A species in the same genus as the Southeast Asian hawk moth Theretra clotho (top right) is capable of not only detecting but actually producing ultrasonic bursts. Other moths (clockwise): Agnosia orneus, Amplypterus panopus, Hayesiana triopus, and Lenyra ashtaroth. From John O. Westwood, The Cabinet of Oriental Entomology (1848).
The combs of honey bees also serve as the dance floors for their distinctive system of communication. The combs of dwarf and giant honey bees (Apis dorsata and Apis florea) in Southeast Asia are built in the open, hanging from branches, and the worker bees dance on the upper surface of the hive in order to “tell” their nestmates where to find resources. The large carpenter bee, Xylocopa chloroptera (upper right), is also depicted along with its nest composed of linear brood chambers in branches. From Horne and Smith, Transactions of the Zoological Society of London (1870).
At its simplest, a laden forager “speaks” to her nestmates through a series of movements called the waggle dance. The bee dances on the vertical comb in the hive in a figure-eight fashion, waggling her abdomen during the middle part of the eight before circling back to do so again, each return cycle alternating between left or right turns. The bee does not waggle during the return runs, only doing so during the middle part of the dance. In addition, she is very specific in the direction in which she orients herself for the waggle run of the dance. It is this orientation that conveys the direction to the source. The world outside is a horizontal landscape, and the bees are dancing on a vertical surface, which means they require an abstract point of reference that they can then convert and use out of the hive. This point of reference is the sun, and a waggle run that is pointed directly up means that the direction is toward the sun. Any deviation, either left or right, from direct up indicates the same degree of deviation outside and relative to the sun. The length of the waggle run correlates to a specific distance from the hive, while the vigor of the performance indicates the relative quality of the food. All of this is taking place within the confines of a dark and crowded hive, and the bees being recruited therefore crowd close to the dancer. Their antennae are placed in close proximity to her, and the Johnston’s organ—that specialized sensory structure that helps to define all insects (see page 8) detects the frequency of vibrations as well as the orientation of the dancer’s body relative to gravity. Collectively, these various elements give sufficient precision for a recruited worker to decide whether or not the food is good enough to visit, and, if so, to depart from the hive in the proper compass direction relative to the sun and fly the necessary distance to find it. There may also be odor cues, such as the scent of the flowers that were visited, that further aid the recruit upon its arrival at the correct location. The language is actually more varied and nuanced than this. For example, should a resource be close enough, then the bee abandons the figure-eight form and does a round dance.
An iconic honey bee (Apis mellifera) skep, or basket, hive from the frontispiece of Moffet’s Insectorum sive Minimorum Animalium Theatrum.
Just as with a human language where there are regional dialects, the same is found among honey bees. Subtle variations are known among distant populations, such as the duration and number of waggle runs correlating to different distances. Thus, a follower from one region “listening” to a dancer from another region will arrive at the wrong location—perhaps going too far or not far enough. They understand the language but don’t quite get the exact meaning. The same is true for all seven species of honey bees, each of which has its own variant of the waggle dance.
Linguists and semioticians forever debate what constitutes language, a concept easily understood but difficult to define. What criteria must be fulfilled in order to satisfy the high standards of a communicative form becoming so labeled? The great founder of semiology, Swiss linguist Ferdinand de Saussure (1857–1913), considered language to require a signifier (“sound-image”) and a signified (“concept”), components both achieved by honey bees. (Interestingly, Saussure’s father was the celebrated entomological taxonomist Henri de Saussure [1829–1905], renowned worldwide for his extensive monographs on Orthoptera and Hymenoptera. One has to wonder whether the communicative calls of the many crickets and katydids his father studied might have stimulated the junior Saussure toward his calling in linguistics.) The symbols and affiliated notions are then arranged according to syntax to form language. Do honey bees have syntax? Yes, since the dance proceeds in an organized and structured fashion, with the particular signs conveyed in an order. For example, waggling does not occur during the return loops, and waggling out of place would lead to confusion, just as writing the words of this paragraph in random order would lose their meaning. A titan among modern linguists, Noam Chomsky (b. 1928) once noted that language was a set of sentences of finite length and constructed of a finite set of elements, and these convey either a finite or infinite range of ideas. Our language is considered “open,” as our range and creativity permit us to generate a seemingly endless possibility of expressions. As far as we know, honey bees are fairly limited in the variety of information conveyed, their language therefore being “closed.” Bees don’t muse about the beauty of a tree or the comforting feel of warm sunshine, nor do they debate whether the squawking of Homo sapiens constitutes a language or not (that we know of, at least). Other schools of thought argue that true language is not innate, i.e., it is not an intrinsic behavior genetically conveyed like most insect communication systems, and yet today’s biolinguists have uncovered that our own foundational capacity for language is ingrained and heritable. Thus, our languages and those of the honey bees seem to sit on a spectrum, distinguished more by a mere degree of complexity and range. For the bees, their dances speak volumes.
The debate over how narrowly or broadly the term language should be used will continue to occupy linguists and philosophers for generations, but no matter how you slice it, an abstract language evolved first among insects. Honey bees have been using a language for at least thirty-five million years, and although the range of ideas that can be expressed is limited, it is nonetheless perhaps one of the most remarkable forms of communication across animals.
FEMININE WIT AND INDUSTRY
A ristotle remained one of the primary sources for information on natural history through the early seventeenth century. Apiculture was already ancient by Aristotle’s age, and the Greek scholar was keeping with convention when he wrote that the leader of a honey bee’s hive was the “king.” The mere inclusion of this idea in Aristotle’s Historia animalium (see page 15) consecrated the concept in the minds of later naturalists. The work of one radical English vicar and beekeeper, however, would overturn this received wisdom, rightly revealing a hive to be a feminine monarchy. Charles Butler was born to an impoverished family in Buckinghamshire in 1560, but his humble origin did not hold him back. In his late teens he was admitted to Magdalen Hall at Oxford, working to support his studies, which in time likely included teaching courses of his own. After ten years of hard effort, Butler completed an arts degree in 1587. Trained in the ministry, following graduation he worked at Magdalen as a Bible clerk until 1593, when he became rector of Nately Scures in Hampshire.
Aside from his ministry, Butler was a logician, grammarian, phonetician, musician, and, most notably, a beekeeper. After moving a couple of times, in 1600, Butler settled down as vicar of the village of Wootton St. Lawrence, remaining there until his passing in 1647. In 1609, Butler published The Feminine Monarchie, the first comprehensive tract on beekeeping in English. The book was of considerable practical use, with instructions on capturing swarms, building hives, and managing the various enemies of the colony. In addition, he wrote of the importance of the bees to gardens and fruit pollination, and even how to use the tone of the bees’ buzzing to predict when a colony was about to abscond and swarm. As a musician, he was so inspired by the sounds of the hive that he even composed a four-part madrigal titled Melissomelos, a transliteration of the tones he perceived the bees to be making (see page 165).
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The title page to the 1634 edition of Charles Butler’s The Feminine Monarchie (1609), in which he employed the phonetic alphabet he developed as a grammarian and phonetician.
Butler demonstrated that the workers produce their wax from the underside of the abdomen—from structures we today call wax mirrors but which are specialized glands—rather than collect it from mysterious sources in the environment. Most importantly, Butler popularized the seemingly heretical notion that the “king” of the hive was, in actuality, a queen, that the drones were the males of the species, and that the workers—whom he praised for their wit and industry (the solertia et labore motto on his book’s frontispiece illustration of a stylized hive, see page 163)—were themselves female. He did not have much empirical evidence for this, but such proof would be forthcoming by the end of the century, when Jan Swammerdam dissected a queen and discovered ovaries therein. Likely unbeknownst to Butler, a Spaniard, Luis Méndez de Torres (see page 129), had also advocated this idea in 1586, but it was Butler’s popular treatise that widely disseminated the feminine rule of bees.
The frontispiece of The Feminine Monarchie, with its stylized honey bee comb. Butler first disseminated the correct notion that the ruler of the hive was a queen, here, depicted with a crown at the top of the hive and surrounded by a retinue of workers and princes (drones).
Butler was so moved by the honey bees he tended and studied that he was inspired to compose a madrigal based on the sounds of the hive. The madrigal, the Melissomelos (opposite), was performed at the dedication of a stained glass window (right) honoring Butler in the parish over which he presided at Wootton St. Lawrence in Hampshire, nearly 350 years after the publication of The Feminine Monarchie. (Parts of the musical notations were printed upside down so two or four singers facing each other could share the book while singing.)
Butler’s The Feminine Monarchie ordained him as the “Father of English Beekeeping.” It is perhaps, however, his 1634 edition that is the most fascinating. As a phonetician and grammarian, Butler pushed for an overhaul of the English language, publishing The English Grammar in 1633, in which he invented an entirely new phonetic alphabet. The revised edition of The Feminine Monarchie that appeared the following year was printed in Butler’s new phonetic system. To commemorate the coronation of Queen Elizabeth II (b. 1926) in 1953, a new stained-glass window, opposite, was installed in the Wootton St. Lawrence church. The window, opposite, depicts Butler holding The Feminine Monarchie, a hexagonal comb surrounding his head and shoulders, much like a halo, with bees arranged in the same formation as in the illustration from the book’s frontispiece. Quite appropriately, the choir performed Melissomelos at the window’s dedication. It may finally be time for Butler to gain a new title as England’s patron saint of apiculture.
Detail of the stick insect Bacteria virgea, from John O. Westwood, The Cabinet of Oriental Entomology (1848) (also see page 172).
“Conceal me what I am, and be my aid
For such disguise as haply shall become
the form of my intent.”
—William Shakespeare
Twelfth Night, Act 1, Scene 2, ca. 1601
The ability to go about undetected is greatly advantageous, whether employed as a form of protection or as a means of stealthily approaching prey. A concealed individual avoids detection, but this is not the same as merely hiding. A truly cloaked individual is not restricted to a single location or cloistered within the confines of a crevice or roost that obscures a plain view of the animal. Instead, through camouflage, mimesis, or mimicry, animals can go about their lives, often in plain sight, yet completely and utterly hidden from others. In any form of disguise, one organism assumes the appearance, behavior, sound, or odor of some model, typically a plant or animal but also sometimes inanimate objects like stones or soil. Even the simplest forms of concealment are considerably complicated. The evolution of such disguises require changes in behavior and anatomy as well as less obviously discerned alterations to the physiology and biochemistry of the mimic. If successfully achieved, to disguise oneself is a powerful asset, and insects are among the best at such deception.
All forms of deception involve various players in order to pull off the act. Foremost is the animal that is hiding, usually dubbed as the mimic, and then there is the species or object it is attempting to resemble, termed the model. The goal is such that by assuming the appearance of the model, the mimic either avoids detection by or confuses a predator, who is appropriately duped. In entomology, camouflage covers a wide range of diverse evolutionary tactics but is usually considered to apply to any use of coloration, materials, anatomy, or behavior to achieve disguise. Most of these fall under what entomologists refer to as crypsis, which simply refers to forms of camouflage that make the insect difficult to see against a particular background.
CAMOUFLAGE
At its simplest, particular colors or patterns permit the insect to seamlessly blend into its surrounding environment. This is commonplace among the animal kingdom, and most insects are suitably patterned. For example, the average desert locust has a pale color suited to its environment, and many grasshoppers living on sandy soil will have mottled patterns rendering them difficult to detect. This simple means of hiding in plain sight is why we can be simultaneously surrounded by insects and yet scarcely ever see them.
The Indonesian stick insect Phasma gigas, illustrated here, can grow up to 9 inches (23 centimeters) in length. While this is impressive, it falls short of the longest record among Phasmatodea, currently held by Phryganistria chinensis of southern China, a species that can extend to 2 feet (61 centimeters). From Georges Cuvier, Le règne animal distribué d’après son organisation (1836–1849).
Different subspecies of the African gaudy grasshopper (Poekilocerus bufonius), whose general coloration and frequently fine mottled spots render it difficult to observe when set among rocky or sandy soil. From Christian Gottfried Ehrenberg, Symbolae Physicae (1828–1845).
A more complex and far less common form of camouflage is the actual construction of a disguise from materials available in the environment. Insects that do this are not otherwise disguised, and without the camouflaging materials they stand out and are fairly obvious to behold. This is not the same as constructing a nest, which, depending on the form and materials, can also blend well into a setting. Instead, camouflage utilizing exogenous materials is built directly onto the insect’s body. It is a remarkably complex feat, and for insects some of the best examples are found among true bugs, bark lice, and lacewings. Nymphal assassin bugs attach plant materials to glandular setae on their bodies, and those in our homes even collect dust or small household debris as part of their camouflage. Bark lice similarly attach debris or even their own feces to glandular setae using silk.
Perhaps most remarkable are the larvae of green lacewings. As larvae, green lacewings are voracious predators of small arthropods, such as aphids or scale insects, making them particularly useful biological control agents whenever such plant-feeding insects make pests of themselves. Most lacewing larvae have specialized knobs and setae on their sides and backs that are used to hold objects in place to cover them. Different species use different materials, but many cover themselves with packets of plant fragments. The larva collects individual pieces and gradually places them onto its back, building up the packet until its body is completely concealed from above, with little more than perhaps its head exposed. The camouflage acts not only as a form of protection for the lacewing, but for certain species it also gives them an advantage when edging up on their prey. Some lacewing larvae will even use the emptied exoskeletons of their prey as material with which to cover themselves, thereby taking on the scent of their chosen victims as part of their disguises. Dressed as a “wolf in sheep’s clothing,” a larva is able to get close to its potential prey, usually undetected until it is too late for some hapless aphid or scale insect. Insects appear to have been the first animals to achieve such complex forms of disguise, as there are fossi
ls of such lacewing larvae, some complete with their disguise still on their backs, from as long ago as 125 million years.
The larvae of green lacewings are famous for building disguises of debris, ranging from plant materials to the carcasses of their prey. Such camouflage permits them to avoid detection by predators and approach their own prey more easily. Shown here are lacewings in various stages of development. Clockwise from top left: a leaf with stalked eggs, a detail of an egg on its stalk, a larva without its camouflage, a larva with a camouflage package of plant debris on its back, and an adult. (Not shown: the pupa and each of the various larval stages.) From Julius T. C. Ratzeburg, Die Forst-Insecten (1844).
MIMESIS
An improvement beyond simple camouflage is achieved through mimesis. Mimesis is where the very form of the insect has evolved such that it outright resembles the shape of the model that is being imitated, usually a plant or other object. Such animals need not seek protective materials from their surroundings in order to build a disguise, as their own bodies are the disguise. We have all been duped by such insects. Stick insects or caterpillars mimetic with twigs, leaf insects nestled among foliage, or thorn bugs sitting along the stems of prickly bushes challenge us to find them even on intense inspection.