ENTOMOLOGY, Economic. Attacks by insects upon useful plants doubtless began with the first cultivation of plants; but it was not until the end of the 18th century that any means for mitigating their ravages were em ployed beyond hand methods and other purely mechanical measures. A few crude efforts were made among the ancient farmers and fruit-raisers on the shores of the Mediterranean toward the suppression of insect pests and Pliny even advised the use of white hellebore, one of the modern insecticides; but it was at about the middle of the 19th century that insecticides (q.v.) or insect poisons began to be generally adopted, and the migration of the Colorado po tato beetle from its native home in the Rocky Mountain region to the potato fields of the East was the indirect means of the employment of arsenical preparations as a means of destroy ing insects; so that this insect, while an appar ent curse, has proved, indirectly, of the great est value to the agricultural community at large. Prior to the use of Paris green, which appears to have first been applied to this potato pest in Michigan in 1867, knocking the beetles from the infested plants into a pan of water was the only method of treatment and was used for many other insects as well. The discovery of the value of this poison as a remedy for the codling moth was made in 1878, by Prof. A. J. Cook, who used Paris green as a remedy for canker-worms and found that the trees treated with it were free from codling moth. To Pro fessor Cook also is probably due the first use of kerosene mixed with soap, although the kerosene emulsion, which is now a standard remedy for all sucking insects, was the joint product of. Messrs. Barnard, Hubbard and Riley, and first used in 1877. White arsenic was employed as an insecticide as early as 1871 and London purple was put to practical use in the destruction of the cotton worm in 1878. London purple has since been displaced by va rious other insecticides, as it has proved in ferior to Paris green, which, in turn, has been replaced by arsenate of lead, because the latter, while poisoning the insects, does not scald or otherwise injure the plants. In the same man ner the discovery of Paris green as a remedy for the Colorado potato beetle was made through the migrations of this insect, the rav ages of the cotton cushion scale (Icerya pur chasi) of the orange orchards of California led to experiments conducted by Mr. D. W. Co
quillett, of the United States Department of Agriculture, in 1886, to the finding of hydrocy anic-acid gas as the best medium for extirpation of scale insects (q.v.), and to its general use in fumigation for all insects which can be treated with it. In 1895 Messrs. A. F. Woods and P. H. Dorsett, also of the Department of Agri culture, began experiments which led to the adoption of a perfected system of fumigation with the same gas of plants grown under glass and injured by scale and other insects.
Our best remedies for insects, then, arseni cal mixtures and kerosene emulsion and other preparations, and hydrocyanic-acid gas, are the product of American research. The bisulphide of carbon as an insecticide, however, though the discovery of a foreigner, has doubtless received greater attention in our country than else where. It was first employed by M. Doyere, as early as 1856, as a remedy for weevils in stored grain, which is still its principal use; but its cost when first employed was so exces sive as to preclude its general employment on a large scale. Subsequently a high grade of this chemical, known as afuma-bisulphide," was made for sale at 10 cents a pound. It supplements the use of hydrocyanic-acid gas in that the former is used for the fumigation of plants above ground, while the latter destroys insects affecting the root-system. Both gases are used for the treatment of indoor insects in granaries and mills and in dwellings and warehouses. Although these are the main insecticides, there are others, nearly all of which owe their dis covery and perfection to economic workers in America. They include pyrethrum, better known as Buhach, Persian and Dalmatian in sect powders, the extensive use of which has resulted in the establishment of a considerable industry in the growing of the principal plants which produce these powders (Pyrethrum cine rarieefolium and Pyrethrum roseum); and whale-oil and fish-oil soaps, originally used against the hop aphis in 1886, and later against scales.