Entomological Roots

A mere 10,000 years ago, primitive hunter—gatherers made a great leap forward; they entered into partnership with plants, and agriculture was born. Thereafter, humans would seek to alter ecosystems to their own advantage. They would intervene to favor some plants and animals over others, thereby altering the evolutionary process that had shaped the biological world for the preceding 4 billion years.

Insects in their coevolution with plants and animals had been a powerful force in shaping the biosphere. They posed a primary threat to humans' alteration of ecosystems to provide food, fiber, shelter, and comfort for themselves and their domestic animals. The struggle that followed moved through stages of ignorance, myth, religion, and then enlightenment through science and technology.

Our brief historical sweep will jump the seemingly long sleep of ancient civilizations and go to the Greek civilization in the time of Aristotle (384-322 B.C.). The orderly study of biology began with his speculations. He relied on his own observations, defined the field, posed the questions, and accumulated evidence to answer them. Aristotle's vision of rationality lay dormant for centuries until the Renaissance. In the meantime, Judaism and Christianity imposed a new concept, one focused on God and creation as depicted in the book of Genesis. Accordingly, God created the world, directing Man to "be fruitful and multiply..." and "with dominion over every living thing that moves upon the earth" (Genesis 1:28). Man was not part of nature. Nature was subservient to Man.

The Scientific Revolution of the 16th and 17th centuries marked the beginning of modern science and included mathematics, mechanics, and astronomy but had little impact on biology. While the revolution rejected superstition, magic, and the dogma of medieval theologians, it did not reject the ideological bias of the Judeo—Christian religion. The hand of God was still directing the course of the natural world.

Not until the 17 th and 18 th centuries was entomology advanced as a field of study within zoology. Anton van Leeuwenhoek (1632—1723) of Holland used the microscope to extend the power of the human eye. He was obsessed with the study of detail, including the morphology and specialized organs of insects. His revelations established insects as proper subjects for scientific study. Francesco Redi (1626-1697) of Italy demonstrated in 1668 that insects arose, not from spontaneous generation, but from eggs laid by fertilized females. Jan Swammerdam (1637-1680) of Holland did superb anatomical work on insects, including the honey bee.

The excitement of these discoveries was further enhanced by the flow of exotic plants and animals brought back from voyages to other continents. Charles Darwin's voyage of HMS Beagle in 1831-1836 followed this tradition. The wealth of material acquired made students aware of the need to classify the organisms collected and to assemble specimens in orderly collections. Other investigators focused on the activity of insects in the field and their role as pollinators and as agricultural pests.

A prerequisite to advancing the study of insects was the development of a classification system that would bring order out of chaos. The Swedish naturalist Carl Linnaeus (1707-1778) met this need. Although trained in medicine, he studied botany extensively and turned to the classification of plants, animals, and minerals. His Systema Naturae (10th ed., 1758) is still regarded as the foundation stone of zoological nomenclature. He greatly simplified insect classification by using insect wings (hence the suffix -ptere, meaning wing, for most order names) as the basis for classification. The other great feature of his system was the designation of genus and species each by a single word, thus providing a binomial system to replace the unwieldy descriptive names employed earlier. Linnaeus's "artificial" system of insect systematics based only on wings was in time modified by adding other characters to construct a "natural" system.

Another great naturalist, René Antoine Ferchault de Réaumur of France (1683-1757), infused a new perspective into the emerging study of insects. He deplored the confusion that existed regarding metamorphosis, distribution, and "industries" of insects. He championed the study of insects out of sheer curiosity, claiming that useful discoveries would be made in the process. His six volumes of Memoires pour Servir a l'Histoire des Insectes (1734-1742) with their exacting attention to morphology and function, complete with accurate drawings, established a new standard of excellence.

The work of Linnaeus and Réaumur provided the templates for orderly classification and elucidation of fundamental and applied aspects of entomology. Their works were extended and refined by French naturalists Pierre Andre Latreille (1762-1833), Georges Cuvier (1769-1832), and Jean Lamarck (1744-1829). By the 19th century, entomology was firmly established in European zoological science. The taxonomic treaties established in this process were to provide the guides to the classification of American insects. These sources were augmented by two sources in Great Britain: Gilbert White's (1720-1793) The Natural History and Antiquities ofSelborne (1789) and William Kirby (1759-1850) and William Spencer's (1783-1860) Introduction to Entomology (1816-1826). The writings of these field naturalists on the biological characteristics of insects made insects, at one point, the most popular component of natural history in Victorian England. In addition, they contributed to the development of the biological species concept. This concept, essential to the understanding of biological communities, recognizes a species as a reproductively (genetically) isolated group of inbreeding populations.

The next step in the unfolding of the biological sciences was a giant one: the publication, in 1859, of Charles Darwin's (1809-1882) theory, On the Origin of Species. This event placed conceptual biology in a new light. In a single stroke, Darwin's work challenged the natural theology that had dominated biological thought for 3 centuries. Natural theology had been elaborated in John Ray's (1627-1705) The Wisdom of God Manifested in the Works of the Creation published in 1691. The concept provided a truce between science and religion. It contended that God created the world and the evidence of His omnipotence was to be found in the study of His creatures.

There was no middle ground between Darwin and Ray. Darwin provided a new way of viewing biology. The living world had evolved; it could be explained on the basis of descent with change. It was noteworthy to entomologists that much of Darwin's supporting evidence was derived from his study of insects dating from his days at Cambridge University (1828), where he was an avid insect collector.

Intense debate followed the publication of Darwin's theory. Nowhere was the debate more intense than at Harvard University, where Asa Gray (1810-1888), a botanist and staunch Darwinian, challenged Louis Agassiz (1807-1873), the foremost naturalist of the world and unrelenting defender of the creationist view.

An unlikely pair of outspoken individuals led the pro-Darwinian entomologists of North America. Benjamin D. Walsh (1801-1869), who had collected beetles with Darwin at Cambridge University, emerged from obscurity on the Illinois frontier to assert his long dormant entomological interest and declare his support for Darwinism. He was joined by the youthful Charles V. Riley (1843-1895), a fellow Englishman and self-taught entomologist who was then writing on entomology for the Prairie Farmer, the leading farm journal of the Midwest (Fig. 1). Their early collaboration on the issue of Darwinism bode well for the future. In time, evolution was accepted by biologists as a

FIGURE 1 Charles V. Riley's nine annual reports as the state entomologist of Missouri (1868-1876) figured prominently in the knowledge base on which the philosophy of insect control in North America was based.

fundamental basis of the discipline, although segments of the public still oppose it as a challenge to the Creation story as reported in the Old Testament book of Genesis. The distinguished geneticist, Theodosius Dobzhansky (1900-1975), summarized the views in the major fields of biology in his essay entitled, "Nothing in Biology Makes Sense Except in the Light of Evolution" (1973).

ENTOMOLOGY IN THE NEW WORLD Nurturing Environment and Supporting Institutions empire and insects Early entomological developments in the United States occurred in the climate of Thomas Jefferson's America. Jefferson took office as the nation's third president in March 1801 and proceeded to sell his vision to his countrymen, then numbering just over 5 million. The United States had only recently gained its independence from England. Louisiana, the land stretching from the Mississippi to the Pacific Ocean, although claimed by Spain, was available and being considered by Russia, France, and England. Of these three, France, energized by Napoleon, was feared the most. Despite the tenuousness of the situation, Jefferson clung to his vision of this vast land mass, stretching from sea to sea, being united under a stable government of the United States. Napoleon's agreement to sell Louisiana came as a surprise; its purchase, although not applauded by some leading politicians, was a masterful stroke. It doubled the land mass of the United States and resolved the feuding over control of the Mississippi River. But what had been purchased? To answer that question, Jefferson dispatched an expedition, led by Captain Meriweather Lewis and Lieutenant William Clark (1804-1805). Commissioned to explore the new acquisition, their report, on their return, removed some of the mystique of the Pacific Northwest but provided only tantalizing glimpses of the area's natural history. Unfortunately, the expedition included no trained naturalists.

The follow-up to Lewis and Clark's report came in 1819-1820. Major Stephen H. Long, under authorization of President Monroe, led an expedition of "Gentlemen of Science" to study this vast unexplored territory, its natural history, and the American Indians of the Rocky Mountain region. Entomology was well represented by Thomas Say, whose affiliation with the Academy of Natural Sciences of Philadelphia had won him the reputation as "perhaps the most brilliant zoologist in the country." Say epitomized the confidence and vision of the young nation's leaders in natural history; he was tall, handsome, and resplendent in the uniform of the Long Expedition, with its high-collared, gold-buttoned, green jacket and black military trousers.

Although Say's primary interest was insects, he covered the entire field of botany and zoology and conducted studies on the American Indians. His entomological studies provided the foundation for his American Entomology, published in three volumes (1824, 1825, and 1828). These were the first books on North American insects. They were beautifully illustrated by the artistic talents of his wife, Lucy, and Titian Peale of the distinguished family of Philadelphia artists. They provided a stimulus for American entomologists and signaled their emancipation from the European centers to which the study of American insects had previously been consigned, named by Europeans, and retained in their collections. With the spirit of the Revolution still vibrant, consigning American insects to European collections offended national pride.

The Long Expedition imparted an American quality to the study of the nation's natural history. The Gentlemen of Science who manned the expedition were trained in the nation's centers of learning. They were not closet naturalists; they were adventurers. Their spirit was described by Say himself: "If our utmost exertions can perform only a part of a projected task, they may, at the same time, claim the praise due to the adventurous pioneer, for removing the difficulties in favor of our successors" (American Entomology).

the cultural centers Natural history found strong support in the cultural centers of Philadelphia, Boston, and New York. Philadelphia led the way, with the American Philosophical Society and the influence of the distinguished Benjamin Franklin (1706-1790). The Academy of Natural Sciences, founded in 1812, nurtured the founding of the

Entomological Society of Philadelphia in 1859, which in turn launched the Practical Entomologist in 1865.

Boston looked to Harvard College and the Massachusetts Society for Promoting Agriculture. William D. Peck (1763-1822) was appointed Professor of Natural History at Harvard in 1805 and offered the first lectures in entomology in North America. Thaddeus William Harris (1795-1853), a physician turned Harvard librarian, found time to become entomological author, teacher, collector, and correspondent. His report on Insects Injurious to Vegetation (1841) summarized the knowledge of insect control in Europe and North America, earning him the title, "Father of Economic Entomology."

New York asserted its interest by appointing Amos Eaton and John E. LeConte to the Lyceum of Natural History of New York. Other distinguished leaders included John Abbot (1751-1840), Thomas Say (1787-1834), and Frederick V. Melsheimer (1749-1814). A striking feature of these men and their institutions was their support of both classical and applied entomology. The individuals were well trained by the standards of the day, often completing training in medicine or theology, because there was no specific training in entomology.

Systematics was the primary entomological interest, followed by aid to agriculture, which was beset with countless insect pests. These leaders experienced the frustration of gaining access to the European literature, founding periodicals for the publications of their own findings, and establishing reference collections.

In the 1840s, American entomologists turned to the task of establishing the institutions that would sever their European dependence. The institutional framework took shape rapidly, led by the American Association for the Advancement of Science (AAAS), founded in 1847. It marked a transition from amateur to professional status, provided a national scientific forum, and nurtured the founding of professional societies. Within approximately 2 decades, 1859 to 1881, five additional societies were established in North America: the Entomological Society of Philadelphia (1859), the Entomological Society of Canada (1862), the Cambridge Entomological Society (1874), the Brooklyn Entomological Society (1872), and the Entomological Club of AAAS (1872). The institutional framework was now in place to expand the scientific and technical dimensions of entomology.

state and federal action in the united states

Agriculture held the key to moving the nation from an agrarian to an industrial society. The farmer was viewed as the noblest and most independent man in society. Unlike in Europe, the availability of fertile soil was seemingly unlimited. While great physical obstacles lay in the path of progress, the greatest was the limits of the human intellect. With these elements in the national outlook, it followed that state and federal action would augment the private efforts in support of agriculture and entomology. In 1854, two landmark appointments were made: Townend Glover was appointed to the Federal Patent Office for work in the newly established Bureau of Entomology, and New York State, responding to pressure from the New York State Agricultural Society, appointed Asa Fitch as its first state entomologist. Illinois and Missouri followed suit in 1868 with the appointments of Benjamin D. Walsh and Charles V. Riley, respectively.

These appointments represented historic landmarks, because state and federal funds were appropriated in support of agriculture with entomology in the vanguard. These men were able individuals whose evangelical zeal and sound professional grounding were attuned to national goals. Their publications, with Charles V. Riley's nine Missouri reports forming the core, laid the foundation for applied entomology in North America.

National goals for agriculture led to enabling federal legislation in three steps. First, the Morrill Land Grant Act of 1862 provided grants to each state, the proceeds from which funded a college, "to teach such branches of learning as are related to agriculture and the mechanic arts... ." A research dimension was added in 1887 by the provisions of the Hatch Act, a state experiment station being added to each college and coordinated by a central office in the Department of Agriculture in Washington, DC. The events cited in the foregoing, occurring within approximately 3 decades, provided an impetus for applied entomology that was unprecedented in the world.

Cooperative Extension, the outreach arm of the Land Grant University, which had been active from the start, was formally recognized and funded by the Smith-Lever Act of 1914. This institutional framework with its catalytic feedback from teaching, research, and extension has been recognized as one of the greatest educational innovations of all time.

With economic entomology rapidly expanding under the stimulus of the experiment stations, Charles V. Riley, now Chief of the Bureau of Entomology, perceived the need for a national organization to advance the goals of economic entomology. His organizational abilities and partnership with his Canadian counterpart, James Fletcher, led to the establishment of the American Association of Economic Entomologists in 1889. At Riley's insistence, the association focused on economic entomology, leaving unmet the needs of the broader dimensions of biology, taxonomy, morphology, and faunistic studies of insects. In 1906, the Entomological Society of America was organized to meet these needs, with John Henry Comstock of Cornell University serving as president. With the various forces that shaped these professional and governmental institutions in mind, we can examine how the institutions responded to the challenge posed by insect pests.

Insect Pests

That the world is not awash in insects, despite their remarkable potential for reproduction, attests to the "balance of nature." But nature's balance, while avoiding extremes, does not preclude insect activity that is annoying to humans. Insects that take humans' crops or blood, and invade their dwellings, are termed "pests." The term has no biological significance; it only expresses a human perception.

Let us examine a few insect outbreaks that occurred in agricultural, medical, and veterinary entomology in the late 1800s. They were to test the mettle of the institutions crafted to address such problems. They taught us much about insects, ourselves, and our vast land mass with its unique biomes and punctuated with its geographical features: the Rockies in the west, the Appalachian range in the east, the Great Plains, the Great Lakes, and the Mississippi. It was this abundance of land that appealed to the early settlers from land-poor Europe. It was from the vastness of the land with its rich flora and fauna coupled with the democratic spirit of its people that the American dream was fashioned. However, the dream's social fabric was not matched by its concept of stewardship of the land. New England's forest primeval had to be breached to make way for agriculture. Conquering nature was viewed as a prelude to progress, and the American Indian and the bison fared poorly under this credo.

agricultural entomology The Colorado potato beetle, Leptinotarsa decemlineata, existed in the foothills of the Rockies on the buffalo bur, Solanum rostratum. As pioneer settlers pushed westward with their crops, the beetle colonized the cultivated potato, Solanum tuberosum, and began its eastern migration along the "potato trail." It was observed as a potato pest in Nebraska in 1859, reached the Atlantic coast by 1874, and traveled thence to Europe in 1876, where it remains an important pest.

The early search for control measures established the arsenical, Paris green, an industrial pigment, as an effective poison. It soon became the standard treatment and was the first widely used poison to kill by ingestion.

The early marketing of insecticides invited fraud through adulteration and false claims. It was not until 1910 that federal legislation was passed requiring labeling to reveal efficacy and ingredients in the two most widely used insecticides, Paris green and lead arsenate.

The boll weevil, Anthonomous grandis grandis, crossed the Rio Grande to Texas in 1894 and began its eastward trek, occupying the entire 1,500,000-km2 cotton belt by 1925. Efforts to impede its progress by establishing no-cotton barriers failed for lack of community compliance. Countless control measures were tried but insecticides eventually won as the first line of defense. Calcium arsenate was adopted for control in about 1920, and its use soon reached 20,000 tons per year. This marked a new scale of area-wide pesticide treatment with its attendant environmental and human safety problems.

The social and economic impact of the weevil was incalculable. The prosperity of the south evolved around a single crop, cotton. With its loss, the economic infrastructure collapsed, and panic ensued. Black laborers left, mortgages were foreclosed, and banks failed. The potential for economic disaster in the wake of insect outbreak was seared in the memory of the people of the cotton-producing states. Only the Civil War had greater impact on the economic and social life of the southern states than did the boll weevil.

The Rocky Mountain grasshopper, Melanoplus spretus, appeared in an epidemic eastward migration, borne on wind currents from the foothills of the Rockies to the Mississippi valley in 1874-1876. Presumably, this migration was in response to the agricultural disruption of the ecosystem that had been dominated by the American bison. The ravages of these hordes of airborne insects created a crisis for the affected states, whose governors appealed to Washington, DC, for federal intervention. In response, the U.S. Entomological Commission was created with the colorful Charles V. Riley as its chairman. This was not a staid Washington bureaucracy; it was a mobile force that reached out to the crisis whenever it arose. Riley scoffed at Sundays devoted to prayer for divine intervention to restrain the pest. Rather, he urged the people to adopt control measures based on intricate knowledge of the life history of the pest. His insights led to bold predictions of the pest's demise from natural causes. With some sound observations and a modicum of luck, his predictions held. The Commission, despite its denials, was credited with solving the problem, bringing new credibility to entomologists and federal aid to the states.

The gypsy moth, Lymantria dispar, was introduced from France, not by accident but by design, by Leopold Trouvelot (1827-1895), a Harvard astronomer and amateur entomologist, who was interested in silk-producing moths. Larvae, emerging from egg masses he had imported, escaped from his Medford, Massachusetts, residence in 1869. After a period of 20 years, the moth reappeared in an epidemic outbreak, it having been mistakenly overlooked as a native species. With this head start, the scorched earth practice of cutting and burning infested trees, augmented by arsenical sprays, failed. The effort did stimulate advances in the technology of spray machines. Today, this introduced pest has spread westward and southward, occupying a swatch from the Great Lakes to the Carolinas.

Biological control was enthusiastically touted following the spectacular success achieved by Charles V. Riley's innovative introduction of the Vedalia, Rodolia cardinalis (Coleoptera), into California to destroy the cottony cushion scale, Icerya purchasi. The pest had been introduced from Australia about 1868 and soon threatened destruction of the state's citrus industry. Two years after the introduction of the predator, the pest was miraculously under control.

The whole array of control measures, cultural, mechanical, chemical, plant resistance, and biological, was employed in seeking to cope with these problems. The entomologists were influenced by expectations and perspectives of their farmer clientele. The farmer's time frame was established by harvest date and sale of the crop; his risk tolerance was low. Insecticides provided immediate and predictable results and they became the backbone of control programs.

Meanwhile, several factors intensified the pressure for insect control, including monoculture, susceptible crops, exacting market standards, and introduced pests; all required greater intervention and modification of the agroecosystem.

medical and veterinary entomology The foundation for modern medical and veterinary entomology was laid by Louis Pasteur, a French microbiologist, who formulated the theory of microbial causation of disease based on his work with the silkworm Bombyx mori in 1887. Without benefit of the germ theory, Josiah Nott, a Mobile, Alabama, physician, proposed (1848) that the causative agents of malaria and yellow fever were transmitted by mosquitoes. In 1881, Carlos Finlay, a Cuban physician, postulated that mosquitoes transmitted the yellow fever agent, setting the stage for Major Walter Reed and associates to verify his claim. In 1897, Ronald Ross demonstrated the occurrence of the malaria parasite in mosquitoes that fed on a human patient whose blood contained the parasite, thus leading to the elucidation of the epidemiology of malaria.

In 1889, Theobold Smith discovered the causative agent of Texas cattle fever and, working with F. L. Kilbowen, showed in 1893 that the cattle tick, Boophilus annulatus, was the vector. Their work paved the way for tick prevention and development of the cattle industry in the southern United States.

The experiences cited above in control of insects of agricultural, medical, and veterinary importance were unprecedented in the American experience and left no region untouched. They revealed the social, political, biological, economic, and environmental dimensions of insect problems. A nation leaning so heavily on agriculture was sensitive to the impact of these problems on the nation's well-being.

The fundamental principles gleaned from these experiences were to shape the philosophy of insect control for the future. They included the following: (1) taxonomic knowledge of the vast insect fauna is a prerequisite for detection and development of control programs; (2) advances in international commerce breach the ancient oceanic barriers to the dispersal of insects and increase the likelihood of introducing exotic species; (3) introduced species, uninhibited by their natural controls, often become major pests in their new habitat; (4) the economic well-being of vast regions of the nation is vulnerable to insect attack; (5) intervention at the federal level is required for insect problems beyond the scope of individual states; (6) alterations of ecosystems trigger changes in patterns of insect behavior; (7) the use of insecticides requires federal regulations to protect the user, the public, and the environment; and (8) an informed public will underwrite sound programs of insect control.

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