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ECONOMIC

ENTOMOLOGY

inner corona. Hale and Frost also photographed the combined bright- and dark-line spectra of the solar cusps at the instants before and after totality. On one photograph showing no dark lines 70 bright lines could be measured between 4070 and 4340. On another were 70 bright lines between Kb and Ks. On a third were 266 bright lines between 4026 and 4381, and some dark lines. These lines show a marked dissimilarity from the solar spectrum. At this eclipse the “shadow-bands” received special attention. These consist of seeming vague and rapidly moving alternations of light and shade flitting over any white surface illuminated by the sun’s rays just before a,nd after the total phase; they are probably due to a flickering of the light from the thin crescent produced by the air, in the same way that the twinkling of the stars is produced. References.—The richest mine of information respecting eclipses of the sun and moon is Oppolzer’s “ Kanon der Finsternisse,” published by the Vienna Academy of Sciences in the 52nd volume of its Denkschriften, Vienna, 1887. It contains elements of all eclipses both of the sun and moon, from 1207 b.c. to a.d. 2161, a period of more than thirty centuries. Appended to the tables is a series of charts showing the paths of all central eclipses visible in the northern hemisphere during the period covered by the table. The points of the path at which the eclipse occurs, at sunrise, noon, and sunset, are laid down with precision, but the intermediate points are frequently in error by several hundred miles, as they were not calculated, but projected simply by drawing a circle through the three points just mentioned. For this reason we cannot infer from them that an eclipse was total at any given place. The correct path can, however, be readily computed from the tables given in the work. Dr Eduard Mahler’s memoir, “Die Centralen Sonnenfinsternisse des XX. Jahrhunderts ” {Denkschriften, Vienna Academy, vol. xlix.), gives more exact paths of the central eclipses of the 20th century, but no maps. General tables for computing eclipses are Oppolzer’s “ Syzygien-tafeln finden Mond” {Publication der Astronomxschen Gesellschaft, xvi.), and Newcomb’s, in Publications of the American Ephemeris, vol. i. part i. Of these, Oppolzer’s are constructed with greater numerical accuracy and detail, while Newcomb’s are founded on more recent astronomical data, and are preferable for computing ancient eclipses. Ginzel’s Spezieller Kanon der Sonnen- und Mondfinsternisse (Berlin, 1899) contains, besides the historical researches already mentioned, maps of the paths of central eclipses visible in the lands of classical antiquity from 900 B.c. to A.D. 500, but computed with imperfect astronomical data. Maguire, “Monthly Notices,” R.A.S., xlv. and xlvi., has mapped the total solar eclipses visible in the British Islands from 878 to 1/24. General papers of interest on the same subject have been published by Rev. S. J. Johnson. A resume of all the observations on the physical phenomena of total solar eclipses up to 1878, by A. C. Ranyard, is to be found in Memoirs of the Royal Astronomical Society, vol. xli. A very copious development of the computation of eclipses by Bessel’s method is found in Chauvenet’s Spherical and Practical Astronomy, vol. i. Hansen’s method is developed in the Abhandlungen of the Leipzig Academy of Sciences, vol. vi. (Math.-Phys. Classe, vol. iv.). The formulae of computation by this method are found in the introductions to Oppolzer’s two works cited above. (s. N.) Economic Entomology is the study of insects based on their relation to man, his domestic animals and his crops, and, in the case of those that are injurious, of the practical methods by which they can be prevented from doing harm, or be destroyed when present. In Great Britain little attention is paid to this important branch of agricultural science, but in America and the British Colonies the case is different. Nearly every State in America has its official Economic Entomologists, and nearly every one of the British Crown Colonies is provided with one or more able men who help the agricultural community to battle against the insect pests. Most, if not all, of the important knowledge of remedies comes from America, where this subject reaches the highest perfection; even the life-histories of some of the British pests have been traced out in the United States and British Colonies more completely than at home, from the creatures that have been introduced from Europe. Some idea of the importance of this subject may be

gained from the following figures. The estimated loss by the Vine Phylloxera in the Gironde alone was £32,000,000; for all the French wine districts £100,000,000 would not cover the damage. It has been stated on good evidence that a loss of £7,000,000 per annum was caused by the attack of the Ox Warble Fly on cattle in England alone. In a single season Aberdeenshire suffered nearly £90,000 worth of damage owing to the ravages of the Diamond Back Moth on the root crops; in New York State the Codling Moth caused a loss of $3,000,000 to apple-growers. Yet these figures are nothing compared to the losses due to Scale Insects, Locusts, and other pests. The most able exponent of this subject in Great Britain was John Curtis, whose treatise on Farm Insects, published in 1860, is still the standard British work dealing with the insect foes of corn, roots, grass, and stored corn. The most important works dealing with fruit and other pests come from the pens of Saunders, Lintner, Riley, Slingerland, and others in America and Canada, from Taschenberg, Lam pa, Reuter, and Kollar in Europe, and from French, Froggatt, and Tryon in Australia. It was not until the last quarter of the 19th century that any real advance was made in the study of economic entomology. Among the early writings, besides the book of Curtis, there may also be mentioned a still useful little publication by Pohl and Kollar, entitled Insects Injurious to Gardeners, Foresters, and Farmers, published in 1837, and Taschenberg’s Praktische Insecktenkunde. American literature began as far back as 1788, when a report on theHessian Fly was issued by Sir Joseph Banks ; in 1817 Say began his writings ; while in 1856 Asa Fitch started his report on the “ Noxious Insects of New York.” Since that date the literature has largely increased. Among the most important reports, &c., may be mentioned those of Riley, published by the U.S. Department of Agriculture, extending from 1878 to his death, in which is embodied an enormous amount of valuable matter. At his death the work fell to Professor Howard, who constantly issues brochures of equal value in the form of Bulletins of the State Department of Agriculture. The chief writings of Lintner extend from 1882 to 1898, in yearly parts, under the title of Reports on the Injurious Insects of the State of New York. Another author whose writings rank high on this subject is Slingerland, whose investigations are published by Cornell University. Among other Americans who have largely increased the literature and knowledge must be mentioned Webster and Felt. In 1883 appeared a work on fruit pests by William Saunders, which mainly applies to the American continent ; and another small book on the same subject was published in 1898 by Miss Ormerod, dealing with the British pests. In Australia Tryon published a work on the Insect and Fungus Enemies of Queensland in 1889. Many other papers and reports are being issued from Australia, notably by Froggatt in N.S. Wales. At the Cape excellent works and papers are prepared and issued by the Government Entomologist, Dr Lounsbury, under the auspices of the Agricultural Department; while from India we have Cotes’s Notes on Economic Entomology, published by the Indian Museum in 1888, and other works, especially on tea pests. Injurious insects occur among the following orders:— Coleoptera, Ilymenoptera, Lepidoptera, Diptera, Hemiptera (both heteroptera and homoptera), Orthoptera, Neuroptera, and Thysanoptera. The order Aptera also contains a few injurious species. Among the Coleoptera or Beetles there is a group of world-wide pests, the Elateridce or Click Beetles, the adults of the various “ Wireworms.” These insects in the larval or wireworm stage attack the roots of plants, eating them away below the ground. The eggs deposited by the beetle in the ground develop into yellowish-brown wire-like grubs with six legs on the first three segments and a ventral prominence on the anal segment. The life of these subterranean pests differs in the various species; some undoubtedly {Agriotes lineatum) live for three or four years, during the greater part of which time they gnaw away at the roots of plants, carrying wholesale destruction before them. When mature they pass deep into the ground and pupate, appearing after a few months as the click beetles (Fig. 1). Most crops are attacked by them, but they are particularly destructive to wheat and other cereals. With such subterranean pests little can be done beyond