In Great Britain the flea beetles (Halticidae) are one of the most serious enemies; one of these, the turnip flea (Phyllotreta nemorum), has in some years, notably 1881, caused more than £500,000 loss in England and Scotland alone by eating the young seedling turnips, cabbage and other Cruciferae. In some years three or four sowings have to be made before a “plant” is produced, enormous loss in labour and cost of seed alone being thus involved. These beetles, characterized by their skipping movements and enlarged hind femora, also attack the 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 paraffin and 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 forest trees suffer from weevils or Curculionidae. The plum curculio (Conotrachelus nenuphar, Herbst) in America causes endless harm in plum orchards; curculios in Australia ravage the vines and fruit trees (Orthorrhinus klugii, Schon, and Leptops hopei, Bohm, &c.). In Europe a number of “long-snouted” beetles, such as the raspberry weevils (Otiorhynchus picipes), the apple blossom weevil (Anthonomus pomorum), attack fruit; others, as the “corn weevils” (Calandra oryzae and C. granaria), attack stored 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 shock. This habit can be used as a means of killing them, by placing boards or sacks covered with tar below the trees, which are then gently shaken. As many of these beetles are nocturnal, this trapping should take place at night. Larval “weevils” mostly feed on the roots of plants, but some, such as the nut weevil (Balaninus nucum), live as larvae inside fruit. Seeds of various plants are also attacked by weevils of the 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 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 pro-legs, which exceeds ten. The female lays her eggs in a slit made by means of her “saw-like” ovipositor in the 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 common to Europe and America; the larva is a curious slug-like creature, found on the upper surface of the leaves of the pear and cherry, which secretes a slimy coating from its skin. Currant and gooseberry are also attacked by sawfly larvae (Nematus ribesii and N. ventricosus) both in Europe and America. Other species attack the stalks of 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 fir plantations, namely, the Siricidae or wood-wasps, whose larvae burrow into the trunks of the trees and thus kill them. For all exposed sawfly larvae 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 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 Halterophora capitata or the Mediterranean fruit fly), the onion fly (Phorbia cepetorum), and numerous corn pests, such as the gout fly (Chloropstaeniopus) and the frit fly (Oscinis frit). Animals suffer from the ravages of bot flies (Oestridae) and gad flies (Tabanidae); while the tsetse disease is due to the tsetse fly (Glossina morsitans), carrying the protozoa that cause the disease from one horse to another. Other flies act as disease-carriers, including the mosquitoes (Anopheles), which not only carry malarial germs, but also form a secondary host for these parasites. Hundreds of acres of wheat are lost annually in America by the ravages of the Hessian fly; the fruit flies of Australia and South Africa cause much loss to orange and citron growers, often making it necessary to cover the trees in muslin tents for protection. Of animal pests the ox warbles (Hypoderma lineata and H. bovis) are the most important (see fig. 2). The “bots” or larvae of these flies live under the skin of cattle, producing large swollen lumps—“warbles”—in which the “bots” mature (fig. 2). These parasites damage the hide, set up inflammation, and cause immense loss to farmers, herdsmen and butchers. The universal attack that has been made upon this pest has, however, largely decreased its numbers. In America cattle suffer much from the horn fly (Haematobia serrata). The dipterous garden pests, such as the onion fly, carrot fly and celery fly, can best be kept in check by the use of paraffin emulsions and the treatment of the soil with gas-lime after the crop is lifted. Cereal pests can only be treated by general cleanliness and good farming, and of course they are largely kept down by the rotation of crops.
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| Fig. 2.—A, Ox Bot Maggot; B, puparium; C, Ox Warble Fly (Hypoderma bovis). |
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| Fig. 3.—Looper-larva of Winter Moth (Cheimatobia brumata). |
Lepidopterous enemies are numerous all over the world. Fruit suffers much from the larvae of the Geometridae, the so-called “looper-larvae” or “canker-worms.” Of these geometers the winter moth (Cheimatobia brumata) is one of the chief culprits in Europe (fig. 3). The 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 lay their eggs by crawling up the trunks of the trees. To check them, “grease-banding” 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 half the apple crop is lost in England owing to the larvae destroying the fruit. Sugar-canes suffer from the sugar-cane borer (Diatioca sacchari) in the West Indies; tobacco from the larvae of 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
