THE INSECT WORLD. 



239 



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 

 Httle creatures attack it, and then its 246. 

 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 weaken 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 



Fruit-bark beetle, Scolytus 



It should be at once cut out and burnt. ruguiosus, much enlarged. 

 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 carboHc 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 feeders must be dealt with as indicated by their life 

 habits, but we must look rather to preventive than to remedial 

 measures in such cases. 



