ENTOMOLOGY (Gr. fvro/.sa, insects, and XO'yos, a dis. course), the science that treats of insects, i.e., of the animals in cluded in the class Insecta of the great phylum Arthropoda. The term, however, is somewhat elastic in its current use, sine( students of centipedes and spiders are often reckoned arnonc 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.
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 of insects to the eastern races was, however, econom ic, religious or moral. The science of insects began with Aris totle, who included in a class "Entoma" the true insects, the arachnids and the myriapods, the Crustacea forming another class ("Malacostraca") of the "Anaema" or "bloodless animals." For nearly 2,000 years the few writers who dealt with zoological subjects followed Aristotle's lead.
The foundations of modern entomology were laid by a series of wonderful memoirs on anatomy and development published in the r 7th and r8th centuries. Of these the most famous are M. Malpighi's treatise on the silkworm (r 669) and J. Swammer dam's Biblia naturae, issued in 1737, 5o 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, r 65r) 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 entomology—indeed to zoology generally—was his theory of pre-formation, which taught the presence within the egg of a per fectly formed but miniature adult. A year before Malpighi's great work appeared, another Italian naturalist, F. Redi, had dis proved 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" form a group equiva lent to the Arthropoda of modern zoologists, and are divided into seven orders, whose names—Coleoptera, Diptera, Lepidoptera, etc., founded on the nature of the wings—have become firmly established. The fascinating subjects of insect bionomics and life- I history were dealt with in the classical memoirs (1734-42) of the Frenchman, R. A. F. de Reaumur, and (1752-78) of the Swede, C. de Geer. From the i8th century until the present day, it is only possible to enumerate the outstanding features in the progress of entomology. In the realm of classification, the work of Linnaeus was continued in Denmark by J. C. Fabricius (Sys tema entoynologica, and extended in France by G. P. B. Lamarck (Animaux sans vertebres, 1801) and G. Cuvier (Lecons d'anatomie comparee, 1800—o5), and in England by W. E. Leach (Trans. Linn. Soc. xi., 1815) . These three authors definitely sepa rated the Arachnida, Crustacea, and Myriapoda as classes distinct from the Insecta. The work of J. O. Westwood (Modern Classi fication of Insects, connects these older writers with their modern successors. Among the latter F. Brauer (1885) laid the foundations of the system of classification used to-day and recognized the fundamental division of insects into the two sub classes Apterygota and Pterygota. Further advances were made by D. Sharp (1899), who first showed the importance of exter nal and internal methods of wing-growth in classification, and other systems were formulated by C. Borner (1 904) and A. Handlirsch (1908) .
In the anatomical field the work of Malpighi and Swammer dam 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. Du four (in a long series of memoirs from 1811-6o) 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 i9th century, as knowledge in creased, the work of investigation became necessarily more and more specialized. Anatomists like F. Leydig, F. Muller, B. T. Lowne and V. Graber investigated in detail some one species or special points in the structure of some particular organs, using in elucidation the ever-improving microscopical methods of research. These investigators were followed by researchers in various fields; among the more notable, B. Grassi, J. Kunckel d'Herculais, A. S. Packard, A. Berlese and F. Silvestri. One of the most important advances in general entomology is due to J. H. Comstock who, with his collaborator, J. G. Needham, laid the foundations of our modern conception of wing-venation, replacing the exist ing chaos by an orderly system. Among other important land marks are N. Wagner's discovery of paedogenesis in the gall midge Miastor (1863) : P. Marchal's discovery of polyembryony in the Chalcids (1898) and F. Silvestri's subsequent researches in that subject. The last mentioned investigator's discovery of the obscure orders Protura in 1907 and the Zoraptera in 1913 is also notable. The difficult subject of the internal changes undergone in the late larva and pupa during metamorphosis is essentially a modern study. Since A. Weismann (1864), J. Van Rees (1885) and A. Kowalevski (1871) laid the basis of these investigations, notable advances have been made by J. Anglas (Iwo), C. Perez (1902-2o), A. Berlese (1900) and others.
The embryology of insects is entirely the study of the last cen tury. C. Bonnet indeed observed in 1745 the virgin reproduction of Aphides, but it was not until 1842 that R. A. von Kolliker de scribed the formation of the blastoderm in the egg of the midge Chironomus. Later A. Weismann traced details of the growth of embryo and pupa among Diptera, and A. Kowalevski, in 1871, first described the formation of the germ layers in insects. Fur ther progress in embryology resulted from improvements in tech nique, and in Germany the subject has attracted a large band of workers among whom V. Graber, K. Heider, R. Heymons, O. BUtschli and H. Henking, may be mentioned. In Russia, N. Kholodkovski was an early embryologist of note and in the United States the researches of W. M. Wheeler are important.
The work of de Reaumur and de Geer in the bionomics and life-history of insects has been continued by nufnerous observers, among whom may be specially mentioned in France E. Perris, J. H. Fabre, C. Janet and C. Ferton. In England the early work ers, W. Kirby and W. Spence, were followed by J. Lubbock (Lord Avebury), L. C. Miall, D. Keilin and others. In the United States a large number of life-histories were elucidated by C. V. Riley; A. S. Packard studied the Lepidoptera, while, concerning Hymenoptera, W. M. Wheeler and G. W. and E. G. Peckham made significant contributions. Experimental entomology is a relatively new and growing subject attracting many workers to day. M. Standfuss, F. Merrifield and E. B. Poulton have studied problems of coloration in this connection, while the effects of temperature and other factors have been investigated by P. Bat chmejew and others. The past history of insects has also at tracted attention. One of the first significant contributions was made by 0. Herr ; S. H. Scudder has studied the insect remains in American rocks, while in Europe, C. Brongniart and A. Handlirsch are outstanding names ; fossils of Australia and elsewhere have been studied with conspicuous ability by R. J. Tillyard.
In the last 3o years or so there have been remarkable develop ments in the study of insects in relation to man and his welfare, and the subject of Economic Entomology (q.v.) has assumed a position of commanding importance. The investigations of insects from the purely utilitarian aspect has also proved a far reaching stimulus to entomology, which to-day can claim a larger band of students and devotees than any other branch of zoology.
After the publication of C. Darwin's Origin of Species (1859) 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 prob lems of animal evolution. The writings of Darwin himself and of A. R. Wallace (both at one time active entomological col lectors) contain much evidence drawn from insects in favour of descent with modification. The phylogeny of insects has since been discussed by F. Brauer, A. S. Packard, A. Handlirsch and many others; mimicry and allied problems of coloration by H. W. Bates, F. Muller, E. B. Poulton, M. C. Piepers, and G. A. K. Marshall; the bearing of insect habits and structure on theories of selection by A. Weismann, G. W. and E. Peckham, G. H. T. Eimer and others : variation was the subject of studies by W. Bateson and M. Standfuss; while problems of heredity have been investigated through the medium of insects by T. H. Morgan and his colleagues, L. Doncaster, R. Goldschmidt and others.
Societies for the discussion and publication of papers on en tomology became established as the number of students grew larger. The Societe Entomologique de France was founded in 1832 and the Entomological Society of London in 1833, similar societies were founded in Breslau in 1839, Holland in 1845, Bel gium in 1855, while one of the first American societies was that of Philadelphia, founded in 1859. In Europe the development and progress of such societies have been largely due to the efforts of men who devoted their leisure time to entomology, though in America it is the professional entomologist who figures largest in such activities. Recognition of the scientific and educational value of entomology as a branch of zoology is a very recent de velopment and has in the main been stimulated by the growing importance of the economic aspects of the subject.
The great amount of literature on entomology that appears annually in various languages far exceeds that on any other branch of zoology. H. A. Hagen's Bibliotheca Entomologica (Leipzig, 1862-63) catalogues all publications up to 1863, while the yearly volumes of the Zoological Record, commencing in 1864, keep the student abreast of the times. An account of the labours of Malpighi, Swammerdam, and other early entomologists is given in L. C. Miall's Lives of the Early Naturalists (1912) and in L. F. Henneguy's Les Insectes (19o4) . Among scientific periodicals devoted to general entomology the Transactions of the Entomological Society of London and the Entomologist's Monthly Magazine are the leading English journals. In France the Bulletin and Annales de la Societe Entomologique de France occupy first place. Among North American periodicals the Canadian Entomologist, Pro ceedings of the Entomological Society of Washington, and the Annals of the Entomological Society of America may be mentioned. Ref erences to the chief literature on entomology are given in the article INSECTS and in those articles devoted to the separate orders.
(G. H. C.; A. D. I.) 'ECONOMIC ENTOMOLOGY Economic entomology is the name given to the study of insects in their relations to man, his domestic animals and crops, and of the practical methods by which the activities of the injurious species may be counteracted. The subject also takes into account those insects that are beneficial to man, either with respect to cer tain economic products which they yield, such as silk, wax and lac, or as agents in controlling other insects which have injurious propensities. It is convenient, therefore, to deal with insects of economic importance under two categories; i.e., species that are injurious and those which are beneficial.