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Insects And Agriculture

( Originally Published 1915 )



Agriculture and the Present School Curriculum.—We expect that the introduction of agriculture into our schools will have a very marked effect in modifying the subject-matter of nature study, and there are those who believe that agriculture will have its most marked effect in modifying the subject-matter of chemistry, physics, botany, zoology and geography. However, it will be better for the pupil, for agriculture and for the other sciences, if agriculture is taught as agriculture with its own subject-matter and its own methods and if the other sciences are taught as distinct and separate sciences. But illustrations of a more practical nature may well be given in the sciences. In botany, for example, we wish the pupils to learn how to know plants, but the seed corn testing box (Fig. 19) makes quite as good a means for illustrating the germination of seeds as does the old planting of the bean or pumpkin seeds; and the germination box makes a better place from which to teach root hairs. In zoology we wish the pupils to learn to know animal life, but there is a good argument against throwing the emphasis on marine animals for pupils in agricultural districts. To be sure what they learn of marine animals is interesting, and something of sea animals is necessary to enable one to get a survey of the animal kingdom. But the child cannot learn everything; we must select the most useful for him.

What I am trying to say is aptly illustrated by a class in zoology in the mid-west. The class was having the emphasis thrown on marine animals because the teacher had been to an eastern summer school where sea life was about all that was studied. When the class came to insects, there was hardly a suggestion that insects were of vital interest to the people of the district. One boy had learned of Professor Snow's work. He saw a field of wheat that was being devastated by the chinch bugs. The boy sent to Professor Snow for some of his cultures. Two little dead bugs covered with a white mould came in a cap box. The boy was instructed by Professor Snow to gather other chinch bugs and fill the cap box, then to wait until the bugs were well inoculated and empty them into a baking-powder box, fill it nearly full of fresh chinch bugs, wait until all were well inoculated and then sprinkle one or two to a square rod around the wheat field. The boy followed directions. The bugs in the field gradually disappeared, the wheat brightened up and the farmer was thankful indeed to science for what it had done for him. But though the boy was taking zoology at the time, he failed, and his teacher was unable to make connections with the field work and the zoology. That boy actually received a lower mark because he was more interested in the outside work, he spent some extra time at it, and failed to make connections with either zoology or botany.

Insects and Nature Study.—Insects offer much valuable material and interesting work to be done any time of year in nature study. But again the teacher needs to be cautioned not to follow a book, unless it be a book like Schmucker's " Study of Nature," in which she is advised to teach the real object and to teach it at such times as she is able to find material. The teacher of insects must have that important attribute of a cultured man or woman which we call open-mindedness. All squeamishness must be put aside and we must go back to nature as little children. They like to handle insects. They do not think of insects " biting." Then, too, teachers must be able to say frequently, and openly and honestly, " I don't know," for there are many things about insects that the most learned scientists do not yet know. No teacher should hope to learn to identify all of the insects, to learn where each spends each period of its life history, or to know offhand how to control each insect. But a teacher should know what books treat of the information which a farmer may need. She should see to it that her library is supplied with one or two good books on insects. Among the good books are Saunder's " Insects Injurious to Fruits," Smith's " Insect Friends and Enemies," and Comstock's " Manual for the Study of Insects."

Teach the Importance of the Subject.—When beginning the study of insects, plant diseases, birds, weeds, or anything else in agriculture for that matter, the teacher should aim to impress upon the minds of her pupils the importance of the subject. In the United States we lose $850,000,000 each year from insects alone. We spend from $3,000,000 to $5,000,000 annually, spraying to control one single insect the codling moth (Fig. 104). In recent years we have introduced the San Jose scale from China, the cotton-boll weevil from Mexico, and we have spread the Colorado potato beetle across a continent. A list of some of the more injurious insects and the injury they do is given in the chapter on birds.

Take Advantage of Transient Interests. If we are to make agriculture popular in our schools, teachers must instruct in the fundamentals first; the special and technical may follow as circumstances demand. By that we mean the general methods of combating insects and plant diseases should be given always, and, when the presence of a certain disease or insect makes it necessary, a series of lessons and a critical study of that particular disease or insect may be given. It is doubtful if, with all our spraying and insecticides, we shall ever be able to check the ravages of the insects unless we can improve the farm practices. At least this seems to be the conclusion of the enlightened European nations that have had similar experiences. The Pacific Coast States are far ahead of the Eastern and the Corn Belt States in recognizing the necessity of a man's seeing that his whole township, county, or State is cleaned up in order for him to keep his own farm free from insects and diseases.

Nature's Beautiful Balance.—Everything has its enemy. Nature would maintain a beautiful equilibrium if she could, but man wishes more than his natural share and hence seeks to destroy the competitors of the plants and animals which he desires to use. One of the most important lessons that man has to learn is that he can control his enemies most easily and economically by increasing their enemies. The first step in con-trolling insects and bacteria is to recognize which ones are beneficial and which are injurious. The second thing to be done is to learn the signs which indicate their presence. Of. both of these matters we shall have more to say later.

Rotation of Crops the First Farm Practice.—The first farm practice to be recommended is the wide rotation of crops. This means, where possible, a complete change of plant families. Some insects live on one kind of plant and some on another, therefore, if a field be plowed and devoted to entirely different plants for a long enough time, the first insects starve for lack of proper food. Some insects and some plant diseases live on corn, some on wheat, some on oats, and others on potatoes. Still others live on corn and the small grains but not on potatoes and tomatoes, or cowpeas and clovers. If the farmer wishes to benefit by this wide rotation-of-crop practice, he must put in as widely differing crops and make the cycle as long as is found by his Experiment Station to be most advantageous. Then, too, he must know when to plow and when to plant. The wheat fields shown in Figs. 94 and 95 are on adjoining farms. The difference came from the fact that one man knew that, to avoid the Hessian fly, he must plant late.

Clean Culture the Second Farm Practice.—The second farm practice to be recommended is thorough, frequent and clean cultivation. The old adage that one acre plowed in August equals two plowed in September, and one plowed in September equals two plowed in October, and so on, applies especially to the destruction of insects, weeds and plant diseases. Disking immediately after harvest helps in two ways : It conserves moisture and thus encourages the multiplication of useful bacteria, and it turns the insects up to the devastation by birds and storms. Many of the insects injurious to fruit pupate in sod, and hence clean culture in an orchard is often effective in ridding it of the insects that cause " wormy fruit." Wire worms, white grubs, canker worms, and corn root lice are among those insects that may be controlled by clean culture. But clean culture has another meaning. Many of the insects and diseases live for part of the season in old and decaying weeds, pieces of bark, twigs, cuttings, etc. ; now clean culture means that these be thoroughly raked and burned. Children should be taught that each " wormy " piece of fruit left in the orchard may mean two hundred " wormy " pieces next year.

The Third Farm Practice, Decoy Crops.—A third farm practice is the planting of decoy crops. This consists of planting, earlier or later than the main crop, along the edge of the garden or field, strips on which the insects will gather. Then the decoy plants and insects are destroyed together, sometimes by spraying with kerosine oil or poison, sometimes by burning, and sometimes by plowing under so as to smother the insects or diseases. A strip of wheat sown in August will often catch the insects of a whole field, and then the wheat on the strip may be destroyed with the insects just before the winter wheat is put in. A strip of mustard or of early cabbages may be used to catch the insects and then be destroyed before they can reach the main crop. Radishes, pumpkins, and other seeds are often planted near the melon hills to catch the melon bugs ; then bugs and decoy plants may be plowed under, burned, or sprayed with oil, Paris green or other preparations.

The Fourth Farm Practice, Pasturing.—Another farm practice to be highly recommended is the pasturing of an infested field with sheep, hogs, horses and cattle ; also the encouraging of the poultry to range as widely over a field as possible. The sheep may eat the weeds that the insects would hibernate on, the hogs may root and eat the grubs, the horses and cattle keep the grass down so that the birds and sunlight get at the insects and diseases most of which thrive best in the shade. One day I found seventeen cut-worms under one cock of hay, and an old Plymouth Rock hen, which for half an hour had been following the men who loaded the hay, ate them all. The next day I found thirty-six cut-worms on the ground from which one cock of clover had been taken; the same old hen ate all and after that lived to be an excellent fall egg layer. Turkeys are better insect destroyers than chickens. It may be necessary to give the caution that many pastures are left down so long that they become infested with insects and diseases peculiar to pasture crops. These old fields can often be made to double their yields by being plowed up and planted to corn or potatoes for a season or two.

The Fifth Farm Practice, Good Planting.—A fifth general farm practice is the planting of crops at a time, and under conditions, when they will get a strong and vigorous start. Corn planted too early on sod gives the cut- and wire-worms (Fig. 96) too long a time to work on the weak and tender plants. Small grains on weak soil often become the prey of diseases and insects that do not injure the same grain on good soil (see Figs. 94 and 95). A soil deficient in one element of fertility often induces a growth that is peculiarly susceptible to disease.

The Sixth Farm Practice, Plant Breeding.—The last general farm practice to which I wish to call attention is the selection of resistant plants and varieties. Individual plants of like species differ greatly in their resistant (see Fig. 23) powers, and varieties differ still more. The Experiment Stations are spending much thought and money on this subject and the farmer boy should. be placed in contact with the results as soon as possible.

One Insect as a Type Study.—At any time when opportunity offers it is well to take up the critical and thorough study of the life history and habits of some one insect that is of economic interest to the particular locality in which a school is located.

Believers in the old faculty, psychology, will find in these exercises splendid material for cultivating the perceptive faculties, for it requires keen sight, good hearing, delicate touch, and often an acute sense of smell to detect the presence of some of the insects. Their preservation, care and feeding will exercise observation, memory and imagination, and no other objects in nature offer better material for the reasoning faculties to work upon. Material for the study of insects may be found every-where (Figs. 96, 97) and at all times of the year. Insect work may be used for the application of lessons from the other branches. Compositions, problems in arithmetic, work in geography and reading may be easily correlated. Telling in a plain way just what the insect has done, may do, or has been known to do ; figuring on the damage done, what percentage of the leaves or plant is injured and what the value is; using the maps to find the place from which the insect originally came, where it was introduced and over what area it has spread ; this and similar work is valuable and adds interest.

A series of lessons on the differences between an insect, a bug, spider, craw-fish, etc., may be given by way of introduction. Then the children should become clearly conscious of the fact that most insects have four stages in their life history. The aim is to enable the child to know thoroughly one insect so that by analogy he may reason intelligently on other insects.

Stages in Life History.—Nearly all insects begin life in an egg. This egg hatches into a larva, or what the children call a " worm " when it is found in apples and other fruits and vegetables. The third stage is the one after this larva has woven a mile or so of silken thread around itself, making a cocoon in which it apparently goes to rest for a time. From this cocoon the pupa emerges as an adult fly, butterfly or moth. School children generally find the work easiest and most interesting by beginning with the cocoon, which may be gathered whenever found and kept in surroundings resembling its natural hibernating place , but under glass so that the children may watch it as it emerges and develops for the first few hours thereafter.

The Subject of Sex.—The teacher will have to use her own judgment about having the sexes mate before the children, in which case the function of the sexes would have to be explained. Many farm children are injured by having the sexual passions stimulated prematurely or too strongly by seeing the mating of farm animals; others are injured by never knowing about such things until they learn of them from the low and degraded. It would seem that the best time for such discussions is in the presence of a pure-minded mother or father before the child reaches the adolescent age. It is a delicate point, but the male and female must mate before the female can lay fertile eggs. Having secured fertile eggs, the pupils should keep them until they hatch into the larvae, and keep the larvae fed until they form the cocoons and become pupae again.

After the pupil has learned the life history of one typical insect his course in agriculture parts company with the old zoology, where men vied with each other in trying to see who could gather, mount and classify the greatest number of specimens—a rather refined kind of pure egotism. The student of agriculture seeks rather to find how many kinds he can learn to identify and control, so as to increase the useful ones and hold in check the injurious ones.

The House Fly. One of the most common insects is the house fly, and yet one will be surprised to learn how few pupils or teachers are sure that they are looking at, or have seen a house fly (Fig. 98). There are many garden insects that look much like house or horse flies; as, for instance, the chalcis fly, the saw fly, the rose-slug, currant-worm fly, etc.

However, the important thing is not learning to identify any particular kind of fly. There are a number of horse flies, all of which have a piercing apparatus with which they make an opening through the skin of the animal and then suck the blood. Some of these, as the little horn fly, are recent importations. As Professor Hodge says, " It is not intended that school children shall make breeding experiments with flies; such disagreeable work may be left for the specialists, but the lessons which every child should learn are that filth breeds flies and that, in spite of the best we can do in keeping our premises clean, we need the help of insectivorous animals. Ask the children to study what the swallows are doing when circling about a herd of cattle ; what the phoebe and king birds do when they dart from their perch and you hear their bills snap. What other birds eat flies? Let some child who has a tame bat see how many flies it will eat: The writer had one that ate 243 at a meal, but it died soon after. Let the children watch the toads about the back-door step, to see how many flies one of them may eat in a day. One little girl counted while a toad snapped 128 flies within a half-hour. A tree frog is a most interesting pet and a wonderful flytrap."

Flies breed in incredible numbers in manure derived prefer-ably from horses. It is claimed that 1200 will emerge from a single pound of horse manure. The female flies lay their eggs in filth and there the eggs hatch into larvae, called maggots, which are readily eaten by birds and chickens, if the filth on the roads and meadows is accessible to them. The females coming from this filth, after laying their eggs, are a dangerous source of contagion. Howard claims that flies are the principal agents for the spread of typhoid fever. We are told that a tubercular cow may void 3,700,000 live tuberculosis germs each day. Human beings afflicted with contagious diseases void many germs. Flies may, and do, spread many of the germs enumerated.

As will be readily seen, there are two important ways of controlling flies, first by the proper care of excreta, and second by destroying the flies (Fig. 99). If excreta is covered with fresh earth or lime, the insects will not frequent it. Ashes do nearly as well as lime. Land plaster used in the horse stable more than pays for itself in fixing the nitrogen in the manure and at the same time helps to keep down the number of flies. If manure is spread, as fast as made, on meadows or pastures the farmer will get the most possible from his manure and at the same time he will avoid breeding places for flies. Manure from the milking yard and barns, if stored, should be easily accessible for the poultry and hogs. The use of fly poisons and fly paper is of course to be recommended. The cone fly trap has been found to be a very effective means of keeping down flies, especially if used early enough in the season.

" The house fly has a number of natural enemies," says Chittenden, " the common house centipede destroys it in considerable numbers ; there is a small reddish mite which frequently covers its body and gradually destroys it; it is subject to attacks from hymenopterous parasites in its larval condition, and it is destroyed by predatory beetles in the same stage. The most effective enemy, however, is a fungus known as Empusa muscoe, which carries off flies in large numbers, particularly toward the close of the season. The epidemic ceases (in the north) in December, and although many thousands are killed by it, the remarkable rapidity of development in early summer months soon more than replaces the thousands thus destroyed." As nearly as we know it, the life history of a fly is as follows: "Egg, from deposit to hatching, one-third of a day; hatching of larva to first moult, one day; first to second moult, one day; second moult to pupation, three days; pupation to issuing of adult, five days; total life cycle, approximately ten days." If each female lays the aver-age number of eggs, i.e., 120, and if one-half of them hatch females which reproduce in ten days, how many flies descend from a single pair in one season, from April to November? Minnesota Extension Bulletin No. 43 says over 214,557,844,-320,000,000,000,000 flies would be produced from one female and her descendants. A Hodge fly trap makes a good manual training project, and the making of one and the keeping of the home place free from flies makes a first rate home project.

The Mosquito.—Another common and injurious insect, that costs the farmers thousands of dollars in blood each season, is the mosquito ; of which, as in the case of the flies, there are a number of species. Again, like the flies, they multiply each spring from a very few adults that survived the winter. The female mosquitoes lay their eggs in water and those in warm, stagnant water hatch into larva known as wrigglers. " But," says Comstock, " it is probable that some species breed in the ground, for mosquitoes occur in arid regions far from water." The ordinary life cycle is ten days and each female, as far as we can learn, lays an average of 200 eggs. Professor Hodge tells us that a single pair, in one average season of 180 days, will produce 2,000,000,000,000,000,000,000,000,000,000,000,000,000 young.

We know that mosquitoes spread a number of diseases, among which are malaria fever and yellow fever. The mosquito, like the horse fly, has a piercing apparatus and injects into his victims a poison which will keep the blood from coagulating while he is drinking. It is believed to be this poison that causes the swelling after a mosquito " bite."

Mosquitoes, like the flies, have a number of insect enemies. The beautiful four-winged dragon-fly (Fig. 100) that we see poised so delicately on weeds and flowers eats large numbers of mosquitoes. Frogs, snakes, minnows, etc., eat large numbers of both eggs and wrigglers, hence fresh water inhabited by these is rarely a source of the mosquito pest. But the most effective method of control seems to be the draining of every stagnant pool and pond, the screening of old barrels (Fig. 101), cisterns, etc., containing soft water, and the application of a small quantity of kerosene oil that may be wafted back and forth on the water that cannot be drained. Nothing but ignorance or indolence can account for the neglect of some farmers to provide good screens for windows and doors to protect the inside of their houses from flies and mosquitoes. Probably the mosquitoes, like the flies, are destroyed in vast numbers by some fungous enemy, but it remains for some bright-eyed boy or girl to discover it and to describe it in an interesting way.

Fleas, Lice and Bedbugs.—Fleas, lice and bedbugs are insects that live upon the blood of man and other animals ; they flourish commonly in homes of ignorance, squalor and carelessness. Each of the farm animals, however, is apt to attract a species of lice peculiar to its kind. In the chapter on pets (under cats and dogs) I mentioned one way of ridding a place of fleas. Chittenden tells us that Professor Gage, in order to rid a building of fleas, " tied sheets of sticky fly paper, with the sticky side out, around the legs of the janitor of the building, who then for several hours walked up and down the floor of the infested room, with the result that nearly all the fleas jumped on to his ankles, as they will always do, and were caught by the fly paper."

Professor Hodge thinks that superhuman tact and good-nature are necessary to enable a teacher to handle successfully the bedbug and lice lessons. Unless their presence in the school, makes the lessons necessary, it is probably better to pass them; but when specimens are found, the opportunity should be taken advantage of to give lessons that will never be forgotten. There are many excellent preparations on the market that destroy very effectively such pests. Some good antiseptic soap should be in every farmhouse at all times. The hair should be washed at least once a month, and in case of bruises, scratches, cuts, also after handling or picking chickens or when one has been in contact with filth on buildings or stock, some antiseptic should be used in the bath water. This is the best insurance against both these loathsome pests and also tetanus, the germs of which give lock-jaw. The tetanus germs live in manure and hence a scratch from an old nail, piece of wire or harness buckle may be very dangerous unless the germs are destroyed by some antiseptic.

There are also good preparations on the market for the different farm animals. The dipping of the farm animals once or twice each season is a good practice and is becoming popular. Some farmers nail old rags saturated with melted lard or tallow mixed with kerosene on to rubbing posts. These padded rubbing posts for cattle and hogs are said to be very effective in holding in check fleas, lice and some diseases such as calf itch, etc.

The Clothes Moth.—Both the fanner and the people in town must make war against the clothes moths. Though not generally considered so, the presence of this insect is due largely to neglect and ignorance of its breeding habits. Let the children discuss freely the losses sustained at their homes from this pest. Then send them home to search in cracks, sheds, and places where old woollens have been neglected or stored, also for bunches of hair or fur that may be lying around, as woollens, fur, hair, etc., are the breeding places of these insects and one of the first things to teach is that all such things should be carefully gathered and burned. Things which we wish to keep from the moths should be tied tightly in cotton cloths, or better, placed in paper sacks which are then pasted shut. Furs and woollens may be stored in trunks that are known to be free from the insects and then the openings of the trunks may be pasted shut. Moth balls, cloves and tobacco are also helpful in driving the pests away, but one does not like the odors afterwards.* Tight screens for the house are very necessary in enabling us to control clothes moths.

There are a number of other household insects such as the buffalo moth, carpet beetle, etc., the presence of which may make necessary one or more lessons on each. Someone has said that " next in value to knowing a thing, is the knowing of where to find out about a thing." We do not expect children to learn everything about insects, but we should teach them that whenever the United States Department of Agriculture or their Experiment Station issues a bulletin about a certain insect it is because that insect is doing great damage, and if the insect is known to be present in their locality the bulletin is worth reading.



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