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Encyclopedia Britannica - Main :: EMS-EUD |
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ENTOMOLOGY (Gr. iv-roa, insects, and Xiryos, a discourse) , the science that treats of insects, i.e. of the animals included in the class Hexapoda of the great phylum (or sub-phylum) Arthropoda. The term, however, is somewhat elastic in its current use, and students of centipedes and spiders are often reckoned among the entomologists. As the number of species of insects is believed to exceed that of all other animals taken together, it is no wonder that their study should form a special division of zoology with a distinctive name.Beetles (Scarabaei) are the subjects of some of the oldest sculptured works of the Egyptians, and references to locusts, bees and ants are familiar to all readers of the Hebrew scriptures. The interest
In the history of the science, various lines of progress have to be traced. While some observers have studied in detail the structure and life-history of a few selected types (insect anatomy and development), others have made a more superficial examination of large series of insects to classify them and determine their relationships (systematic entomology), while others again have investigated the habits and life-relations of insects (insect bionomics). During recent
The foundations of modern entomology were laid by a series of wonderful memoirs on anatomy and development published in the 17th and 18th centuries. Of these the most famous are M. Malpighi's treatise on the silkworm (1669) and J. Swammerdam's Biblia naturae, issued in 1737, fifty years after its author's death, and containing observations on the structure and life-history of a series of insect types. Aristotle and Harvey (De generatione animalium, 1651) had considered the insect larva as a prematurely hatched embryo and the pupa as a second egg. Swammerdam, however, showed the presence under the larval cuticle of the pupal structures. His only unfortunate contribution to entomologyindeed to zoology generallywas his theory of pre-formation, which taught the presence within the egg of a perfectly formed but miniature adult. A year before Malpighi's great work appeared, another Italian naturalist, F. Redi, had disproved by experiment the spontaneous generation of maggots from putrid flesh, and had shown that they can only develop from the eggs of flies.Meanwhile the English naturalist, John Ray, was studying the classification of animals ; he published, in 1705, his Methodus insectorum, in which the nature of the metamorphosis received due weight. Ray's " Insects " comprised the Arachnids, Crustacea, Myriapoda and Annelida, in addition to the. Hexapods. Ray was the first to formulate that definite conception of the species which was adopted by Linnaeus and emphasized by his binominal nomenclature. In 1735 appeared the first edition of the Systema naturae of Linnaeus, in which the " Insecta " forma group ' equivalent to the Arthropoda of modern zoologists, and are divided into seven orders, whose namesColeoptera, Diptera
Arachnida
In the anatomical field the work of Malpighi and Swammerdam was at first continued most energetically by French students. P. Lyonnet had published in 176o his elaborate monograph on the goat-moth caterpillar, and H. E. Strauss-Durckheim in 1828 issued his great treatise on the cockchafer. But the name of J. C. L. de Savigny, who (Mem. sur les animaux sans vertebres, 1816) established the homology of the jaws of all insects whether biting or sucking, deserves especial honour. Many anatomical and developmental details were carefully worked out by L. Dufour (in a long series of memoirs from 1811 to z86o) in France, by G. Newport (" Insecta " in Encyc. Anat. and Physiol., 1839) in England, and by H. Burmeister (Handbuch der Entomologie, 1832) in Germany. Through the 19th century, as knowledge increased, the work of investigation became necessarily more and more specialized. Anatomists like F. Leydig, F. Muller, B. T. Lowne and V. Graber turned their attention to the detailed investigation of some one species or to special points in the structure of some particular organs, using for the elucidation of their subject the ever-improving microscopical methods of research. Societies for the discussion and publication of papers on entomology were naturally established as the number of students increased. The Societe Entomologique de France was founded in 1832, the Entomological Society of London in 1834. Few branches of zoology have been more valuable as a meeting-ground for professional and amateur naturalists than entomology, and not seldom has the amateuras in the case of Westwooddeveloped into a professor. During the pre-Linnaean period, the beauty of insectsespecially the Lepidopterahad attracted a number of collectors; and these " Aurelians "regarded as harmless lunatics by most of their friendswere the forerunners of the systematic students of later times. While the insect fauna of European countries was investigated by local naturalists, the spread of geographical exploration brought ever-increasing stores of exotic material to the great museums, and specialization either in the fauna of a small district or in the world-wide study of an order or a group of familiesbecame constantly more marked in systematic work. As examples may be instanced the studies of A. H. Haliday and H. Loew on the European Diptera
Hagen on the North American Neuroptera, of D. Sharp
The embryology of insects is entirely a study of the last century. C. Bonnet indeed observed in 1745 the virgin-reproduction of Aphids, but it was not until 1842 that R. A. von Kolliker described the formation of the blastoderm in the egg of the midge Chironomus. Later A. Weismann (18631864) traced details of the growth of embryo and of pupa among the Diptera, and A. Kovalevsky in 1871 first described the formation of the germinal layers in insects. Most of the recent
The work of de Reaumur and de Geer on the bionomics and life-history of insects has been continued by numerous observers, among whom may be especially mentioned in France J. H. Fabre and C. Janet, in England W. Kirby and W. Spence, J. Lubbock (Lord Avebury) and L. C. Miall, and in the United States C. V. Riley. The last-named may be considered the founder of the strong company of entomological workers now labouring in America. Though Riley was especially interested in the bearings of insect life on agriculture and industryeconomic entomology (q. v.)he and his followers have laid the science generally under a deep obligation by their researches. After the publication of C. Darwin's Origin of Species (18J9) a fresh impetus was given to entomology as to all branches of zoology, and it became generally recognized that insects form a group convenient and hopeful for the elucidation of certain problems of animal evolution. The writings of Darwin himself and of A. R. Wallace (both at one time active entomological collectors) contain much evidence drawn
Spencer
B1sL1oGRArxv.References to the works of the above authors, and to many others, will be found under HExAronA and the special articles on various insect orders. Valuable summaries of the labours of Malpighi, Swammerdam and other early entomologists are given in L. C. Miall and A. Denny's Cockroach (London, 1886), and L. Henneguy's Les Insectes (Paris, 1904). (G. H. C.) End of Article: ENTOMOLOGY (Gr. iv-roa, insects, and Xiryos, a discourse) If you wish, you can link directly to this article.
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