. Economic entomology for the farmer and fruit-grower. Beneficial insects. THE INSECT WORLD. 239 Fig. Fruit-bark beetle, Scolytus rugulosus, much enlarged. These insects rarely attack sound, healthy trees, and this is a peculiarity of bark-beetles in general, though there are many exceptions. But just as soon as a tree becomes a little weakened through injury or from starvation, these little creatures attack it, and then its doom is sealed, unless vigorous meas- ures are taken at once. Peach-trees are especially susceptible to injury, and the gummy oozings from the little holes seem to v
. Economic entomology for the farmer and fruit-grower. Beneficial insects. THE INSECT WORLD. 239 Fig. Fruit-bark beetle, Scolytus rugulosus, much enlarged. These insects rarely attack sound, healthy trees, and this is a peculiarity of bark-beetles in general, though there are many exceptions. But just as soon as a tree becomes a little weakened through injury or from starvation, these little creatures attack it, and then its doom is sealed, unless vigorous meas- ures are taken at once. Peach-trees are especially susceptible to injury, and the gummy oozings from the little holes seem to vi^eaken them so rapidly that they succumb in a short time. It is good practice to keep orchard trees in the best possible health and vigor at all times to enable them to resist naturally the attacks of these insects, but if one does become seriously infested it should be at once cut out and burnt. It is certain to die in a short time, and it is a constant menace to surrounding trees from the abundance of specimens which will be produced, ready to attack others at the least sign of weakness. Where a slight infestation is noticed on a tolerably healthy tree, it should be closely examined to ascertain the original source of weakness, and when this is re- moved the tree should be stimulated by means of appropriate fertilizers, and the trunk kept covered by whitewash to which Paris green has been added. Strong whale-oil soap-suds will answer the same purpose, and a little crude carbolic acid will add to its effectiveness. In all cases the application should be thorough, and should be kept intact until the tree has fully recovered and is able to take care of itself. The same line of treatment is adapted to other bark-beetles, varied according to the differences in life history. To recapitulate in a general way, beetles and their larvae are mandibulate and chew their food ; therefore, whenever they feed openly upon plant tissues, they may be killed by arsenical sprays. Internal feeder
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