THE WAR ON INSECTS 293 



quently used as winter washes for tree trunks. In a 

 solution of one pound in one gallon of water we have a 

 mixture which kills lichens and' mosses on tree trunks 

 as well as many spores of fungi, and leaves the bark 

 in a nice, clean, shining condition, vigorous and free 

 from all clogging organisms. It is astonishing what an 

 improvement a wash of this kind will often produce on 

 fruit and shade trees, and where a clean healthy bark 

 is a desideratum, there is no better way to obtain it. 

 Besides cleaning the bark, this material will also corrode 

 and destroy many of the thinner scales such as the 

 species of Chionaspis of which the scurfy scale is an 

 example. That species hibernates in the egg state, and 

 the egg is not affected by the caustic ; but the scale 

 covering is thin, easily corroded, and the eggs are then 

 washed out and scattered by rains. Those larvae that 

 hatch from them will rarely be able to find their way 

 back to the tree, and in most instances the eggs them- 

 selves perish under the unnatural conditions. A ma- 

 terial so caustic as this should be carefully handled, 

 for sores caused by it frequently ulcerate badly and 

 heal very slowly, because of the destruction of tissue. 



Lime is one of the most useful materials on the 

 farm from a great many points of view. Few insects 

 care to rest voluntarily on a lime-covered surface; 

 only hunger will induce most species to eat through it, 

 and some will not touch it under any circumstances. 

 Lime in its various forms is about the only material 

 used by most European orchardists, and whitewashed 

 trees form a characteristic feature in many localities. 

 As a whitewash on fences and farm buildings generally, 

 inside and out, it covers over or fills crevices and cavi- 

 ties that w^ould otherwise serve as hiding places for 

 insects. It seals up and destroys the eggs of such insects 

 as may be present when the wash is applied, and on 



