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ECONOMIC ENTOMOLOGY
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ECONOMIC See also:ENTOMOLOGY , the name given to the study of See also:insects based on their relation to See also:man, his domestic animals and his crops, and, in the See also:case of those that are injurious, of the See also:practical methods by which they can be prevented from doing harm, or be destroyed when See also:present. In See also:Great See also:Britain little See also:attention is paid to this important See also:branch of agricultural See also:science, but in See also:America and the See also:British colonies the case is different. Nearly every See also:state in America has its See also:official economic entomologists, and nearly every one of the British See also:crown colonies is provided with one or more able men who help the agricultural community to See also:battle against the See also:insect pests. Most, if not all, of the important knowledge of remedies comes from America, where this subject reaches the highest perfection; even the See also:life-histories of some of the British pests have been traced out in the See also:United States and British colonies more completely than at See also:home, from the creatures that have been introduced from See also:Europe.
Some See also:idea of the importance of this subject may be gained from the following figures. The estimated loss by the See also:vine See also:Phylloxera in the See also:Gironde alone was £32,000,000; for all the See also:French See also:wine districts £roo,000,000 would not See also:cover the damage. It has been stated on See also:good See also:evidence that a loss of £7,000,000 per annum was caused by the attack of the ox warble See also:fly on See also:cattle in See also:England alone. In a single See also:season See also:Aberdeenshire suffered nearly £90,000 See also:worth of damage owing to the ravages of the See also:diamond back See also:moth on the See also:root crops; in New See also:York state the codling moth caused a loss of $3,000,000 to See also:apple-growers. Yet these figures are nothing compared to the losses due to See also:scale insects, locusts and other pests.
The most able exponent of this subject in Great Britain was See also: Among the See also:early writings, besides the bookof 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. See also:American literature began as far back as 1788, when a See also:report on the See also:Hessian fly was issued by See also:Sir See also:Joseph See also:Banks; in 1817 Say began his writings; while in 1856 See also:Asa See also: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 C. V. Riley, published by the U.S. See also:Department of See also:Agriculture, extending from 1878 to his See also:death, in which is embodied an enormous amount of valuable See also:matter. At his death the work See also:fell to See also:Professor L. O. See also:Howard, who constantly issues brochures of equal value in the See also:form of Bulletins of the U.S. Department of Agriculture. The See also:chief writings of J. A. Lintner extend from 1882 to 1898, in yearly parts, under the See also:title of Reports on the Injurious Insects of the State of New York. Another author whose writings See also:rank high on this subject is M. V. Slingerland, whose investigations are published by Cornell University. Among other Americans who have largely increased the literature and knowledge must be mentioned F. M. See also:Webster and E. P. See also:Felt. In 1883 appeared a work on fruit pests by See also: At the Cape excellent works and papers are prepared and issued by the See also:government entomologist, Dr Lounsbury, under the auspices of the Agricultural Department; while from See also:India we have See also:Cotes's Notes on Economic Entomology, published by the See also:Indian Museum in 1888, and other works, especially on See also:tea pests.
Injurious insects occur among the following orders: See also:Coleoptera, See also:Hymenoptera, See also:Lepidoptera, See also:Diptera, See also:Hemiptera (both heteroptera and homoptera), See also:Orthoptera, See also:Neuroptera and See also:Thysanoptera. The See also:order See also:Aptera also contains a few injurious See also:species.
Among the Coleoptera or bettles there is a See also:group of See also:world-wide pests, the Elateridae or click beetles, the adults of the various " wireworms." The insects in the larval or See also:wireworm See also:stage attack the roots of See also:plants, eating them away below the ground. The eggs deposited by the See also:beetle in the ground develop into yellowish-See also: For root-feeders, bisulphide of See also:carbon injected into the See also:soil is of particular value. One See also:ounce injected about 2 ft. from an apple See also:tree on two sides has been found to destroy all the ground form of the woolly aphis. In See also:garden cultivation it is most useful for wireworm, used at the See also:rate of 1 ounce to every 4 sq. yds. It kills all root pests. In Great Britain the See also:flea beetles (Halticidae) are one of the most serious enemies; one of these, the See also:turnip flea (Phyllotreta nemorum), has in some years, notably 1881, caused more than Soo,000 loss in England and See also:Scotland alone by eating the See also:young seedling turnips, See also:cabbage and other See also:Cruciferae. In some years three or four sowings have to be made before a "plant" is produced, enormous loss in labour and cost of See also:seed alone being thus involved. These beetles, characterized by their skipping movements and enlarged See also:hind femora, also attack the See also:hop (Haltica concinna), the vine in America (Graptodera chalybea, Illig.), and numerous other species of plants, being specially harmful to seedlings and young growth. Soaking the seed in strong-smelling substances, such as See also:paraffin and See also:turpentine, has been found efficacious, and in some districts paraffin sprayed over the seedlings has been practised with decided success. This oil generally acts as an excellent preventive of this and other insect attacks. In all climates fruit and See also:forest trees suffer from weevils or Curculionidae. The See also:plum curculio (Conotrachelus nenuphar, Herbst) in America causes endless harm in plum orchards; curculios in Australia ravage the vines and fruit trees (Orlhorrhinus klugii, Schon, and Leptops hopei, Bohm, &c.). In Europe a number of " See also:long-snouted " beetles, such as the See also:raspberry weevils (Otiorhynchus picipes), the apple blossom See also:weevil (Anthonomus pomorum), attack fruit; others, as the "corn weevils" (Calandra oryzae and C. granaria), attack stored See also:rice and corn; while others produce swollen patches on roots (Ceutorhynchus sulcicolLis), &c. All these Curculionidae are very timid creatures, falling to the ground at the least See also:shock. This See also:habit can be used as a means of killing them, by placing boards or sacks covered with See also:tar below the trees, which are then gently shaken. As many of these beetles are nocturnal, this trapping should take See also:place at See also:night. Larval " weevils " mostly feed on the roots of plants, but some, such as the See also:nut weevil (Balaninus nucum), live as larvae inside fruit. Seeds of various plants are also attacked by weevils of the See also:family Bruchidae, especially beans and peas. These seed-feeders may be killed in the seeds by subjecting them to the fumes of bisulphide of carbon. The corn weevils (Calandra granaria and C. oryzae) are now found all over the world, in many cases rendering whole cargoes of corn useless. The most important Hymenopterous pests are the sawflies or Tenthredinidae, which in their larval stage attack almost all vegetation. The larvae of these are usually spoken of as " false caterpillars," on See also:account of their resemblance to the larvae of a moth.. They are most ravenous feeders, stripping bushes and trees completely of their foliage, and even fruit. Sawfly larvae can at once be recognized by the curious positions they assume, and by the number of See also:pro-legs, which exceeds ten. The See also:female See also:lays her eggs in a slit made by means of her "saw-like" ovipositor in the See also:leaf or fruit of a tree. The pupae in most of these pests are found in an earthen cocoon beneath the ground, or in some cases above ground (Lophyrus pini). One species, the slugworm (Eriocampa limacina), is See also:common to Europe and America; the larva is a curious slug-like creature, found on the upper See also:surface of the leaves of the See also:pear and See also:cherry, which secretes a slimy coating from its skin. See also:Currant and See also:gooseberry are also attacked by sawfly larvae (Nematus ribesii and N. ventricosus) both in Europe and America. Other species attack the stalks of See also:grasses and corn (Cephus pygmaeus). Forest trees also suffer from their ravages, especially the conifers (Lophyrus pini). Another group of Hymenoptera occasionally causes much harm in See also:fir plantations, namely, the Siricidae or See also:wood-wasps, whose larvae burrow into the trunks of the trees and thus kill them. For all exposed sawfly larvae See also:hellebore washes are most fatal, but they must not be used over ripe or ripening fruit, as the hellebore is poisonous. The order Diptera contains a See also:host of serious pests. These two-winged insects attack all kinds of plants, and also animals in their larval stage. Many of the adults are bloodsuckers (Tabanidae, Culicidae, &c.); others are parasitic in their larval stage (Oestridae, &c.). The best-known dipterous pests are the Hessian fly (Cecidomyia destructor), the pear midge (Diplosis pyrivora), the fruit flies (Tephritis Tyroni of Queensland and B (Hypoderma bovis). set up inflammation, and cause immense loss to farmers, herds-men and butchers. The universal attack that has been made upon this pest has, however, largely decreased its See also:numbers. In America cattle suffer much from the See also:horn fly (Haematobia serrata). The dipterous garden pests, such as the See also:onion fly, See also:carrot fly and See also:celery fly, can best be kept in check by the use of paraffin emulsions and the treatment of the soil with See also:gas-See also:lime after the See also:crop is lifted. Cereal pests can only be treated by See also:general cleanliness and good farming, and of course they are largely kept down by the rotation of crops. Lepidopterous enemies are numerous all over the world. Fruit suffers much from the larvae of the Geometridae, the so-called "looper-larvae"or " canker-See also:worms." Of these geometers the See also:winter moth (Cheimatobia brumata) is one of the chief culprits in Europe (fig. 3). The See also:females in this moth and in others allied to it are wingless. These insects pass the pupal stage in the ground, and reach the boughs to See also:lay their eggs by crawling up the trunks of the trees. To check them, " grease-banding " See also:round the trees has been adopted; but as many other pests eat the leafage, it is best to kill all at once by spraying with arsenical poisons. Among other notable Lepidopterous pests are the " surface larvae " or cutworms (Agrotis spp.), the caterpillars of various Noctuae; the codling moth (Carpocapsa pomonella), which causes the maggot in apples, has now become a universal pest, having spread from Europe to America and to most of the British Colonies. In many years quite See also:half the apple crop is lost in England owing to the larvae destroying the fruit. See also:Sugar-canes suffer from the sugar- See also:cane borer (Diatioca sacchari) in the See also:West Indies; See also:tobacco from the larvae of See also:hawk moths (Sphingidae) in America; corn and grass from various Lepidopterous pests all over the world. Nor are stored goods exempt, for much loss annually takes II place in corn and See also:flour from the presence of the larvae of the Mediterranean flour moth (Ephestia kuniella); while furs and clothes are often ruined by the clothes moth (Tinea trapezella). By far the most destructive insects in warm climates belong to the Hemiptera, especially to the Coccidae or scale insects. All fruit and forest trees suffer from these curious insects, which in the female See also:sex always remain apterous and apodal and - live attached to the bark, leaf and fruit, hidden beneath variously formed scale-like coverings. The male scales differ in form from the female; the adult male is winged, and is rarely seen. The female lays her eggs beneath the scaly covering, from which See also:hatch out little active six-legged larvae, which wander about and soon begin to form a new scale. The Coccidae can, and mainly do, breed asexually (parthenogenetically). One of the most important is the See also:San Jose scale (Aspidiotus perniciosus), which in warm climates attacks all fruit and many other trees, which, if unmolested, it will soon kill (fig. 4). These scales breed very rapidly; Howard states one may give rise to a progeny of 3,216,080,400 in one See also:year. Other scale insects of See also:note are the See also:cosmopolitan See also:mussel scale (Mytilaspis pomorum) and the Australian Icerya purchasi. The former attacks apple and pear; the latter, which selects See also:orange and citron, was introduced into America from Australia, and carried ruin before it in some orange districts until its natural enemy, the A See also:lady-See also:bird beetle, Vedalia cardinalis, was also imported. FIG. 5.-The Hop Aphis (Phorodon humuli). A, Winged female; B, winged After the Coccidae the next most important insects male; C, ovigerous wingless female; D, viviparous wingless female from economically are the plant lice or A plzididae. These breed Plum ; E, pupal stage. with great rapidity under favourable conditions: one by the end of the year will be accountable, according to See also:Linnaeus, for the enormous number of a quintillion of its species. See also:Aphides are See also:born, as a See also:rule, alive, and the young soon commence to reproduce again. Their See also:food consists mainly of the See also:sap obtained from the leaves and blossom of plants, but some also live on the roots of plants (Phylloxera vastatrix and Schizoneura lanigera). Aphides often ruin whole crops of fruit, corn, hops, &c., by sucking out the sap, and not only check growth, but may even See also:entail the death of the plant. See also:Reproduction is mainly asexual, the females producing living young without the agency of a male. See also:Males in nearly all species appear once a year, when the last female See also:generation, the ovigerous generation, is fertilized, and a few large ova are produced to carry on the continuity of the species over the winter. Some aphides live only on one species of plant, others on two or more plants. An example of the latter is seen in the hop aphis gallons of soft See also:water, and add 2 oz. of lime and a small quantity of agricultural See also:treacle; the latter is prepared by dissolving 3 oz. of acetate of See also:lead in a little water,' then i oz. of arsenate of soda in water and mixing the two well together, and adding the whole to 16 gallons of soft water; to this is added a small quantity of coarse treacle. For piercing-mouthed pests like Aphides no See also:wash is of use unless it contains a basis of soft See also:soap. This soft-
soft-
soap wash kills by contact and may be prepared in the following
Wooll (Schizoneura lanigera) of the and it, y aphis ( apple pear: way :—Dissolve 6 to 8 lb of the best soft soap in boiling soft water secretes tufts of See also: In this treatment we have to See also:bear in mind what the entomologist teaches us, that is, the nature, habits and structure of the pest, For insects provided with a biting mouth, which take nourishment from the whole leaf, shoot or fruit, the poisonous washes used are chiefly arsenical. The two most useful arsenical sprays are See also:Paris green and arsenate of lead. FIG. 4.—San Jose Scale (Aspidiotus perniciosus). A, Male scale insect; To make the former, mix i oz. of the Paris green with 15 B, female; C, larva; D, female scale; E, male scale. D (Phorodon humuli), which passes the winter and lives on the sloe and damson in the See also:egg stage until the See also:middle of May or later, and then flies off to the hops, where it causes endless harm all the summer (fig. 5); it flies back to the prunes to lay its eggs when the hops are ripe. Another aphis of importance is the paraffin oil and See also:churn well together with a force-See also:pump; the whole may then be mixed with See also:ioo gallons of soft water. The oil readily separates from the water, and thus a perfect emulsion is not obtained : this difficulty has been solved by Mr See also:Cousin's paraffin See also:naphthalene wash, which is patented, but can be made for private use. It is prepared as follows:—Soft soap, 6 lb dissolved in i quart of water; naphthalene, to oz. mixed with 12 See also:pint of paraffin; the whole is mixed together. When required for use, t lb of the See also:compound is dissolved in 5 to to gallons of warm water. These two washes are essential to the well-being of every See also:orchard in all climates. Not only can we now destroy larval and adult insects, but we can also attack them -in the egg stage by the use of a See also:caustic See also:alkali wash during the winter; besides destroying the eggs of such pests as the Psyllidae, red spider, and some aphides, this also removes the vegetal encumbrances which shelter numerous other insect pests during the See also:cold part of the year. Caustic alkali wash is prepared by dissolving i -lb of crude potash and t lb of caustic soda in soft water, mixing the two solutions together, adding to them lb of soft soap; and diluting with to gallons of soft water when required for use. Another approved insecticide for scale insects is See also:resin wash, which acts in two ways: first, corroding the soft scales, and second, fixing the harder scales to stop the See also:egress of the. hexapod larvae. It is prepared as follows :—First crush 8 lb of resin in a See also:sack, and then place the resin in warm water and See also:boil in a cauldron until thoroughly dissolved; then melt to lb of caustic soda in enough warm water to keep it liquid, and mix with the dissolved resin; keep stirring until the mixture assumes a clear See also:coffee-See also:colour, and. for ten minutes afterwards; then add enough warm water to bring the whole up to 25 gallons, and well stir. See also:Bottle this off, and when required for use dilute with three times its bulk of warm soft water, and spray over the trees in the early See also:spring just before the buds burst. For mites (Acari) See also:sulphur is the essential ingredient of a spray. See also:Liver of sulphur has been found to be the best form, especially when mixed with a paraffin emulsion. Bud mites (Phytoplidae, fig. 6) are of course not affected. Sulphur wash is made by adding to every to gallons of warm paraffin emulsion or paraffin-naphthaleneemulsion 7 oz. of liver of sulphur, and stirring until the sulphur is well mixed. This is applied as an See also:ordinary spray. Nursery stock should always be treated, to kill scale, aphis and other pests which it may carry, by the gas treatment, particularly in the case of stock imported from a See also:foreign See also:climate. This treatment, both out of doors and under See also:glass, is carried out as follows:—Cover the plants in bulk with a See also:light gas-tight See also:cloth, or put them in a See also:special fumigating See also:house, and then place t oz. of See also:cyanide of See also:potassium in lumps in a dish with water beneath the covering, and then pour 1 oz. of sulphuric See also:acid over it (being careful not to inhale the poisonous fumes) for every moo cub. ft. of space beneath the cover. The gas generated, prussic acid, should be See also:left to work for at least en See also:hour before the stock is removed, when all forms of See also:animal life will be destroyed. For spraying, proper See also:instruments must be used, by means of which the liquid is sent out over the plants in as See also:fine a mist as possible. Numerous pumps and nozzles are now made by which this end is attained. Both See also:horse and See also:hand See also:machines are employed, the former for hops and large orchards, the latter for See also:bush fruit and gardens. In America, where trees in parks as well as orchards and gardens are treated, See also:steam-See also:power is sometimes used. Among the most important sprayers are the Strawson horse sprayers and the smaller Eclair and Notus knapsack pumps, carried on the back (fig. 7). The nozzles for " mistifying " the wash most in use are known as the See also:Vermorel and Riley's, which can be fitted to any length of tubing, so as to reach any height, and can be turned in any direction. The pumps in the See also:machine keep the insecticide constantly mixed, and at the same time force the wash with great strength through the nozzle, and so to the exterior; as a fine mist; every part of the plant is thus affected. Beneficial Insects have also to be considered in economic entomology. They are of two kinds—(r) those that help to keep down an excess of other insects by acting either as parasites or by being insectivorous in habit; and (2) insects of economic value, such as the See also:bee and silkworm. Amongst the most important See also:friends to the See also:farmer and gardener are the Hymenopterous families of See also:ichneumon flies (Ichneumonidae and Braconidae); the Dipterous families Syrphidae and Tachinidae; the Coleopterous families Coccinellidae and Carabidae; and the Neuropterous Hemerobiidae, or lace-wing flies. Ichneumon flies lay their eggs either in the larvae or ova of other insects, and the parasites destroy their host. In this way the Hessian fly is doubtless kept in check in Europe, and the aphides meet with serious hindrance to their increase. If a number of .plant-lice are examined, a few will be found looking like little pearls; these are the dried skins of those that have been killed by Ichneumonidae. The Syrphidae, or hover flies, are almost exclusively aphis-feeders in their larval stage. Trichina flies attack lepidopterous larvae. One of the most notable examples of the use of insect See also:allies is the case of the Australian lady-bird, Vedalia cardinalis, which, in common with all lady-birds, feeds off Aphidae and Coccidae. The Icerya scale (Icerya purchasi) imported into America ruined the orange groves, but its enemy, the Vedalia, was also imported from Australia, and counteracted its abnormal increase with such great results that the crippled orange groves are now once more profitable. (F. V. Additional information and CommentsThere are no comments yet for this article.
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