loss at 40 per cent. Add to this loss the $8,250,000 spent yearly for spraying and the codling moth has caused us a loss of nearly $20,000,000 yearly. The damage to stored products is greater than is realized. Tobacco, truck crops and cereals are attacked by worms, beetles, weevils and moths. The food waiting consumption at the house is visited by larder and ham beetles, various flies and moths. Mr. Marlatt is then justified in his statement: "The losses resulting from the depredations of insects on all the plant products of the soil, both in their growing and in their stored state, together with those of live stock, exceed the entire expenditures of the National Government, including the enormous pension roll and the maintenance of the Army and Navy." The damage done to domestic animals by such insects as gadflies, botflies, screw-worm flies, ticks and lice is put at $175,000,000 yearly.20 We must also keep in mind the enormous burden imposed upon agriculturists by the growth of weeds, the yearly loss in the United States being estimated at $100,000,000. Weeds affect agriculture in many ways. If plowed under they may furnish humus and thus be valuable. When growing in cultivated fields, however, they are injurious. They may form a dense mat on the ground which holds moisture, invites insects and may introduce disease. In other cases they may use water needed for crops. If it takes several hundred pounds of water to produce one pound of dry stalks the loss may be serious for the crop. Furthermore, weeds may appropriate a considerable part of the plant food in the soil and finally they may smother the crop by their dense rank growth. The wild plants, native or introduced, frequently show such virility that their destruction is extremely difficult. Whenever man plows a field and plants his crop, he destroys thereby the bulk of the native flora. Now it may be that some one or two species are so persistent that they find the new conditions with the soil mellow and only the cultivated plants as competitors most favorable, and develop to the extent of occupying the ground and balking the farmer's hopes. In the Eastern states this frequently takes place whenever the native honeysuckle starts in a grass field. Even more common perhaps is the introduction of some new plant, frequently with the seed of the desired species. A very large part of the weeds in our country have been introduced from Europe. Chickweed, dandelion, plantain, Canada thistle and burdock are a few which every farmer knows. Gray's Botany of 1887 listed 2,893 species of native plants and 405 introduced - a goodly percentage of the latter must be classed as weeds. Weeds, incidentally, are plants for which we have no use, or are useful plants growing where they are not wanted. In the South, Johnson grass, a species of sorghum, is one of the most valuable fodder plants. In a cultivated field it is however the despair of the planter. 20 Year Book of Department of Agriculture, 1904, p. 461 ff. Man engages therefore in a ceaseless warfare to protect his plants and insure crops. He must move his strawberry bed every year or two, not alone because of the rapid increase of the plants, but because of the growth of grass; he must change his hayfields, not merely for the sake of rotating crops, but chiefly to get rid of the weeds. The expert tells from the weeds on a farm the grade of the farmer. To keep undesired species from growing is thus a very important part of agriculture. Animals have food preferences, but what they actually eat is often more or less a matter of chance or necessity. It is interesting to note that the alimentary canal in carnivora is from three to five times as long as the body, while in herbivora it is from eleven to twenty-six times as long as the body. The fact that in man it is but seven times the body length may indicate that he is likely to cling to a meat diet. Fortunately for man seeds and insects are the chief food supply of many animals, especially the birds. Some oneseventh of our birds are primarily seed eaters. The great family of finches and sparrows find seventy-five per cent of their food in seeds of weeds. The proven record of the bob-white is amazing. Number of Seeds Eaten by a Bob-white in One Day One hundred and twenty-nine different weeds are known to furnish food to the bob-white. "In Bulletin No. 21, Biological Survey, it is calculated that if in Virginia and North Carolina there are four bob-whites to every square mile, and if each bird consumes one ounce of seed per day, the total destruction to weed seeds from September 1st to April 30th in those states alone will be 1,341 tons." 21 Bob-white is partial to insects also. It is known to eat 145 species including such harmful varieties as the Colorado potato beetle, chinch-bug, wireworm, May beetle, squash beetle, cotton boll weevil, cutworm, codling moth and Hessian fly. 21 HORNADAY, W. T. Our Vanishing Wild Life, p. 220. Taking the year as a whole, 73 per cent of the meadow lark's food is insects, 12 per cent weed seeds, 5 per cent grain. The crow blackbird eats insects 26.9 per cent; other animal food, 3.4 per cent; corn, 37.2 per cent; oats, 2.9 per cent; wheat, 4.8 per cent; other grain, 1.6 per cent; fruit, 5 per cent and weed seeds and mast, 18.2 per cent. The robin's diet consists of insects, 40 per cent; wild fruits, 43 per cent; cultivated fruit, 8 per cent; vegetables, 5 per cent. The fly-catchers feed almost wholly upon insects, while the great army of warblers are not far behind - 95 per cent. Over 65 per cent of the food of woodpeckers is insects. A fair breakfast for a mourning dove is put at three thousand grass seeds. The song sparrow will eat some 1,500 larvæ a day, while the yellow-throated warbler will consume 10,000 tree lice in the same time. A scarlet tanager has been known to devour 35 gypsy moths a minute for 18 minutes. More than 50 different species feed upon caterpillars, while 38 species live largely on plant lice. Five hundred mosquitoes have been found in the crop of one night hawk. Thirty-six species of birds feed on the codling moth, chief of which are woodpeckers, titmice and sparrows, in some places destroying from 66 to 85 per cent of the larvae. The great group of snipe, sandpipers and plover eat beetles, weevils, worms, mosquitoes and grasshoppers. The swallows are the greatest enemies in this country of the cotton boll weevil. It is claimed that in the state of Iowa there are about 89,000,000 birds, each of which eats not less than 25 insects per day, or a daily total of 2,240,000,000 or about 18,666 bushels of insects each day for the 150 days of the warmer months. exact censuses show a 50 per cent increase in the birds during the last four years." 32 After twenty-five years of agitation the government of the United States began in 1913 the control of all migratory birds, its law supplanting all state laws, determining the conditions under which they may be killed and sold. The importation of egret plumes, etc., has been prohibited. Mrs. Sage has given Marsh Island in the Gulf of Mexico to the government as a bird refuge. The success here has stimulated similar movements in Europe. Game preserves are being established by both state and national governments as well as by private citizens. It is not too much to hope that we are entering a new era in our relations to nature. The control to be discussed in the next chapter is the direction of nature's forces to produce the maximum of good to ourselves not the reckless and shortsighted display of mere brute force and the destruction of the very basis of our life. SUGGESTIONS FOR READING BRAUN, MAX. Animal Parasites of Man. 1906. DARWIN, CHARLES. The Formation of Vegetable Mould Through the Action of Worms. 1881. DRUMMOND, H. The Ascent of Man. 1894. FABRE, J. H. Social Life in the Insect World. 1912. 66 HERTER, C. A. HORNADAY, W. T. Our Vanishing Wild Life. 1912. Wild Life Conservation in Theory and Practice. 1914. KROPOTKIN, P. Mutual Aid. 1902. |