entomology

entomology,

study of insectsinsect,invertebrate animal of the class Insecta of the phylum Arthropoda. Like other arthropods, an insect has a hard outer covering, or exoskeleton, a segmented body, and jointed legs. Adult insects typically have wings and are the only flying invertebrates......Click the link for more information., an arthropod class that comprises about 900,000 known species, representing about three fourths of all the classified animal species. Insects are studied because of their importance as pollinators for fruit crops; as carriers of bacterial, viral, and fungal diseases; as parasites of humans or livestock; as destroyers of economically important plants; or as predators of other destructive insects. The role of insects in ecosystems and their control by insecticides or by biological methods are studied in ecologyecology,study of the relationships of organisms to their physical environment and to one another. The study of an individual organism or a single species is termed autecology; the study of groups of organisms is called synecology......Click the link for more information.. Some insects such as the fruit flyfruit fly,common name for any of the flies of the families Tephritidae and Drosophilidae. All fruit flies are very small insects that lay their eggs in various plant tissues......Click the link for more information., Drosophila, are used in the laboratory to study geneticsgenetics,scientific study of the mechanism of heredity. While Gregor Mendel first presented his findings on the statistical laws governing the transmission of certain traits from generation to generation in 1856, it was not until the discovery and detailed study of the.....Click the link for more information.; others are used to study behavior and physiology. The ability to increase productivity of insect populations that supply commercially important products such as dyes, silk, and honey and the deliberate introduction of insect diseases into populations of insect pests involves knowledge of microbiology and biochemistry as well as entomology.

Entomology

the science of insects; an extensive branch of zoology. Initially, entomology studied all the arthropods; however, because of the vast number of insect species (exceeding the number of plant, microorganism, and the remaining animal species combined), it gradually restricted itself to the class Insecta (seeINSECTA). The other arthropod classes became the subjects of various independent sciences, for example, arachnology (the study of spiders) and carcinology (the study of crustaceans). A number of specialties evolved within entomology as a result of the study of insects by orders and families, such as coleopterology (the study of beetles), lepidopterology (the study of butterflies and moths), and myrmecology (the study of ants).

Modern entomology is a multidisciplinary science that studies the structure and life activities of insects and their individual and historical development, diversity, global distribution in time and space, and relationship with the environment. Depending on its tasks, it is subdivided into general entomology and applied entomology. General, or theoretical, entomology deals with the morphology of insects (external morphology, as well as anatomy, histology, and cytology), insect embryology, the study of metamorphosis, the physiology, ethology, and ecology of insects, insect geography, paleoentomology, and taxonomy. Applied entomology is concerned with harmful insects, such as crop and food pests, parasites, and transmitters of human, animal, and plant diseases, as well as with beneficial insects, that is, those that supply products useful to man, such as the honeybee (the object of apiculture) and the Asiatic silkworm and the tussah (the objects of sericulture), natural enemies of pests, plant pollinators, and soil formers.

History. Interest in insects dates to remote antiquity. Man was long familiar with the damage inflicted by insects and long made use of beneficial insects. Assyrian cuneiform tablets and Egyptian papyri of the third millennium B.C mention the devastating onslaughts of locusts. Chinese manuscripts of the same period contain references to the raising of silkworms and efforts to control garden pests. The Greek philosopher Aristotle (fourth century B.C.), who identified the entorna group among the “bloodless animals,” summarized the known information about insects.

However, it was not until the 17th century that entomology emerged as a science. Its foundation was laid by the work of the Dutch scientist J. Swammerdam on the anatomy and development of the bee (1669), by the work of the Italian scientists M. Malpighi (1686) and F. Buonanni on the anatomy and development of the silkworm and the structure of the insect mouth apparatus, respectively, and by the work of the German scientist J. Gödart on the types of metamorphosis. In the 17th century the first attempt to classify insects was made (British scientist J. Ray). Multivolume compendiums on insects appeared in the 18th century, including Mémoires pour servir a l’histoire des insectes (vols. 1–6, 1734–42) by the French scientist R. de Reaumur, who discovered parthenogenesis in aphids (1737); the five-volume work containing observations of insects by the German scientist A. Rösel von Rosenhof; and Mémoires pour servir à l’histoire des insectes (vols. 1–7, 1752–78) by the Swedish naturalist C. de Geer, who conducted comparative morphological studies of insect larvae. The study of the entomofauna of extensive areas was begun in the mid-18th century, when the Swedish scientist C. Linnaeus described the entomofauna of Sweden (1746, 1761). Similar research was carried out for various parts of Russia, especially the steppe zone, by the Russian scientist P. S. Pallas (1771–76), for Austria by F. Schrank (1781), and for Italy by P. Rossi (1790). Linnaeus’ work laid the foundations of modern taxonomy. In his Systema naturae (10th ed., vols. 1–2, 1758–59), Linnaeus described 1,936 insect species, which he first grouped into genera and then, on the basis of wing structure, into nine orders. He also introduced the binary nomenclature to systematize the scientific names of species (the nomenclature is retained because of its priority).

In the 19th century, the British entomologists W. Kirby, J. Westwood, and J. Lubbock, who identified several additional orders, introduced their own insect classifications. The French entomologist P. Latreille (1831) proposed a classification system that in extent more or less corresponds to the present class. With the appearance of C. Darwin’s Origin of Species (1859), the classification of insects became based on the phylogenetic principle (the Austrian scientist F. Brauer and the American scientist A. Packard). Brilliant research was carried out on insect anatomy by the French scientist L. Dufour and on metamorphosis by J. H. Fabre in France, A. Weismann in Germany, and I. A. Porchin-skii and A. O. Kovalevskii in Russia. The Russian scientist N. P. Vagner discovered a new type of parthenogenesis called paedogenesis (1862). A. A. Tikhomirov induced artificial parthenogenesis in silkworms (1886). M. S. Ganin described a new type of development of Hymenoptera (1869). N. V. Bobretskii and N. A. Kholodkovskii determined the developmental characteristics of Díptera (1878) and Orthoptera, respectively. P. I. Bakhmet’ev began studying anabiosis (1897). A. O. Kovalevskii discovered germ layers in insects, one of the most important theoretical generalizations in embryology (1869–71). The French zoologist P. Marchal discovered polyembryony (1898). The German scientist V. Graber (1897) and others compiled compendiums of insect embryology. The French scientist F. Plateau (1870) carried out important research on the physiology of insect respiration and digestion.

Throughout the 19th century, extensive material on the entomofauna of many countries and continents was amassed by major scientific expeditions and individual scientists (the Russian G. I. Fischer von Wal’dheim, author of the five-volume Entomography of Russia [1820–51], P. P. Semenov-Tian-Shanskii, N. M. Przheval’skii, and V. I. Roborovskii). Basic reference works appeared at the turn of the 20th century on the insects of Europe (Beetles of Russia and Western Europe; fases. 1–11, 1905–15), America (about 40 volumes of Central American Biology, 1879–1915), Madagascar (six volumes of Natural History of Madagascar, 1889–1900), the Hawaiian Islands (1899–1913), and India (1887–1932).

Development in the 20th century. The 20th century has been marked by the gathering of a great deal of factual material on the world’s entomofauna, by extensive taxonomical work, by important discoveries, and by research in all fields of theoretical and applied entomology. The number of insect species known to science has increased to 1 million (2 to 3 million species are believed to exist), and hundreds of new species are discovered every year. About 35 to 40 orders have been identified. Insect classification systems have been reorganized and improved (the Austrian scientist A. Handlirsch, the American scientist H. Crampton, and the Soviet paleoentomologist A. V. Martynov), and new (fundamentally similar) systems have been proposed (the Soviet ecologist M. S. Giliarov, 1969; the Italian entomologist G. Grandi, 1970; the Australian scientist I. MacKerras, 1970). The traditional taxonomical methods, such as comparative morphological methods, are now supplemented by more sophisticated ones using computers (electron microscopy, karyosystematics). Increasing use is being made of numerical taxonomy (the American scientist R. Sokal) and taxonomic analysis (the Soviet scientist E. S. Smirnov and others). All this has made it possible to refine the phytogeny of various insect groups and to improve insect classification.

Insect morphology as the basis of taxonomy has been extensively investigated by entomologists of many countries. Organs have been studied in close association with their functions (the school of the American scientist R. Snodgrass, 1935; the Soviet scientist A. V. Martynov, 1924, 1938). Much research has been conducted on insect physiology: tracheal respiration (the Danish scientist A. Krogh), excretion (the British scientist V. B. Wigglesworth), the unique features of vision and other sensory organs, and the ability of insects to perceive polarized light and guide themselves by it (the German scientist K. von Frisch).

The phenomenon of photoperiodism has played a major role in the development of insect physiology (the Soviet zoologist A. S. Danilevskii, the Dutch scientist J. de Wilde, and others). The elucidation of its mechanism will help solve many important practical problems for example, the forecasting of natural insect populations. The insect central nervous system was found to secrete hormones (the Polish scientist S. Kopec, 1917); also discovered were the ecdysones, which induce molting (A. Butenandt, 1943), and the juvenile hormone, which regulates development (C. M. Williams, 1956). Recently discovered analogs of the juvenile hormone (of plant origin or chemically synthesized) and antihormones (the American scientist W. Bowers, 1976) are currently being studied as possible agents for controlling pests.

Insect biochemistry has become an independent branch of entomology, especially after the publication in 1961 of the handbook of the Australian scientist D. Gilmour. The discovery of behavior-controlling pheromones excreted by insects (A. Butenandt, Federal Republic of Germany, and others) has stimulated the study of insect behavior, an area of research that dates back to the works of the French naturalists R. Réaumur and J. H. Fabre, among others.

Twentieth-century ethology has been freed of the anthropomorphism (interpretation of insect behavior in human terms) characteristic of 18th-century natural science and has been given a rigorous scientific foundation. This was an important development, resulting in the discovery of the “language of the bees” in the mid-20th century (the German zoologist K. von Frisch). Insect ethology has become a major field of research in modern entomology.

Insect ecology is now widely studied (the first major contributions were made by the American scientists V. Shelford in 1913 and R. Chapman in 1931). While studying the relationship between insects and the environment, the German scientist H. Blunck demonstrated (1922) that their rate of development varied with the temperature of the surroundings. The complex relationship between insects and the plants they pollinate (entomophilous plants), which had attracted Darwin’s attention (1862), were generalized by the Norwegian biologist K. Faegri (1975). The elucidation of plant-aphid relations helped reconstruct the historical geography of many groups of higher plants (the Soviet scientist A. A. Mordvilko, 1935). The significance of insect symbiosis with some microorganisms was clarified (the German scientist P. Buchner, 1912, and others).

A new branch of insect ecology has evolved—the study of phase variability; that is, the morphological and physiological characteristics and behavior of insects vary with the population density (the Russian scientist B. P. Uvarov, the school of the French zoologist P. Grasse, the Soviet scientist A. G. Sharov). Soviet scientists generalized the ecological regularities of insect distribution. They established the rules of the zonal change of habitats (G. Ia. Bei-Bienko, 1930, 1964) and the change of strata (M. S. Giliarov, 1951). The study of insect ecology has helped elucidate the main paths of insect evolution (M. S. Giliarov, 1949).

Insect geography has made considerable advances. In 1936 the Soviet entomologist A. P. Semenov-Tian-Shanskii, studying the areas of distribution of some insect species, worked out the division of the Palaearctic into zoogeographic provinces. The boundaries of the zoogeographic regions of South America were later similarly delineated (the French scientist C. Delamare and the Venezuelan scientist E. Rapoport), as were those of Antarctica and Oceania (the American scientist J. L. Gressitt). The Swedish entomologist C. Lindroth investigated (1959) the connections between the Eurasian and North American entomofaunas. In the USSR, some zoogeographic regions were described in detail from the insect complexes (for example, Central Asia by O. L. Kryzhanovskii, 1965).

Research on paleoentomology was begun in the mid-20th century. At the beginning of the 19th century, only 219 species of fossil insects were known. Today, more than 12,000 fossil forms are known, and paleontology is not limited to describing them but also studies the paleoecology of insects. Many large taxons and successions of insect faunas in different geological epochs have been studied. The Soviet school of paleoentomologists (A. V. Martynov, B. B. Rodendorf, and others) has major achievements to its credit. Paleoentomological data are used to determine the paths of insect evolution.

Insects have become important experimental animals (for example, Drosophila in genetics and the darkling beetle in population genetics).

Applied entomology. Applied entomology began developing at the turn of the 20th century. Its considerable practical value has long been known because of the vast number of harmful insects, the study of which has led, with increasing knowledge and improved methods of control, to the subdivision of applied entomology into agricultural entomology (field-crop, fruit, and vegetable pests), forest entomology (forest pests), and medical and veterinary entomology (bloodsucking insects and transmitters of contagious and parasitic diseases of humans and animals).

The first specialized studies in agricultural and forest entomology appeared in the 19th century (the research of the German scientist J. Ratzeburg on forest pests, 1837–44; the work of the German scientist H. Nórdlinger on field, orchard, and garden pests, 1869; the work of the German scientist J. Kaltenbach on agricultural pests, 1874; and the research of the Russian scientist F. P. Keppen on agricultural and forest pests, 1881–83). The economic damage inflicted by insects, especially locusts and phylloxeras, necessitated the centralization of research and the application of control measures on a nationwide scale. Hence, many countries organized state entomological services to protect plants from pests.

The post of provincial entomologist was instituted in Russia in 1887, an entomology office was organized in the Department of Agriculture in 1894, and the first entomological station was established in 1904. In the USSR, plant protection was placed on a scientific and planned basis. In 1929 the All-Union Institute of Plant Protection was founded, with a network of regional stations. The Ministry of Agriculture of the USSR organized a service to record and forecast insect infestations. Research in agricultural entomology was coordinated by scientific councils established by the Academy of Sciences of the USSR and the Lenin All-Union Academy of Agricultural Sciences. Ineffective mechanical methods of pest control (barrier and trap ditches, sticky strips) were replaced by better methods: chemical methods (pesticides), biological methods (the use of predatory and parasitic insects and microorganisms pathogenic to insects), and special farming methods that create unfavorable conditions for the reproduction and development of pests. A combination of these approaches results in an integrated system of control (seePLANT PROTECTION). All this has enabled applied entomology to make substantial contributions to increased agricultural and silvicultural productivity. A. S. Serebrovskii in the USSR, D. North in the United States, and others outlined the principles of genetic control of pests.

Medical entomology began developing with the study of mosquitoes, the transmitters of malaria (the Russian scientist V. Ia. Danilevskii, 1888, and the Italian scientist G. B. Grassi, 1901). The role of other bloodsucking insects in spreading many dangerous diseases of animals and man was also elucidated (the data were generalized by the German scientist E. Martini, 1923 and 1941, and by others). In the USSR, the work of V. N. Beklemishev on malarial mosquitoes and the work of E. N. Pavlovskii, who developed the theory of the natural geographical foci of transmissible (by insects and other arthropods) diseases of animals and man, played a major role in promoting medical and veterinary entomology. Practical measures have been developed for the effective protection of people and farm animals from dangerous diseases transmitted by insects.

Institutes, societies, publications, and congresses. In the USSR, the general aspects of entomology are studied at the Zoological Institute of the Academy of Sciences of the USSR, the Institute of Evolutionary Morphology and Animal Ecology, and the zoological institutes of the Union republics. Research in agricultural and forest entomology is conducted at the All-Union Institute of Plant Protection, at institutes of plant protection of the Union republics, and at specialized branches of other research institutes. Research in medical entomology is carried out at the Institute of Malaria and Parasitic Diseases of the Academy of Medical Sciences of the USSR. The All-Russian Entomological Society (now the All-Union Entomological Society) was founded in 1859.

The leading entomological periodicals in the USSR are Entomologicheskoe obozrenie (Entomological Review) and Trudy Vsesoiuznogo entomologicheskogo obshchestva (Transactions of the All-Union Entomological Society). Detailed descriptions of insects in various parts of the USSR are included in the multivolume Fauna of the USSR (similar works are published in many other countries). Abstracts of world entomological literature are published in the Referativnyi zhurnal: Biologiia (Journal of Abstracts: Biology), Biological Abstracts, and Entomology Abstracts, while abstracts of articles on practical entomology are published in the Review of Applied Entomology. International entomological congresses are held periodically (the first was held in Oxford, England, in 1910, and the 15th, in Washington, D.C., in 1976).

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