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. [Illustration: FIG. 2.--A, Ox Bot Maggot; B, puparium; C, Ox Warble Fly (_Hypoderma bovis_).] [Illustration: FIG. 3.--Looper-larva of Winter Moth (_Cheimatobia brumata_).]