THE WAR ON INSECTS 295 



powder, it is useful against a great variety of viscid or 

 moist slugs, like those of the asparagus, potato, pear and 

 the like. When slacked in this way the fine particles of 

 lime are still very caustic and need another particle of 

 water to complete the slacking. If, in this condition, the 

 lime is dusted on the moist slugs, each particle of lime 

 gets the desired particle of water from the body of the 

 slug, and in doing so burns a little hole into the skin. 

 The effectiveness of a dry lime application, therefore, 

 depends on the moist condition of the insect to be 

 dealt with, and in consequence early morning appli- 

 cations when there is a little dew are always most 

 effective. In the asparagus fields where once the slugs 

 have gotten a start after the cutting season is over, 

 there is nothing better than a cloud of dry hydrate of 

 lime put on with a powder gun just at sunrise or a little 

 before. 



This reference to the time of application in order to 

 reach the insects in the best condition brings to mind 

 that there are some plants and insects that by reason 

 of a waxy or powdery surface or covering repel or shed 

 water particles. The woolly lice and mealy bugs are 

 insect examples and the cabbage leaves are good plant 

 examples. When cabbage plants are attacked by 

 Aphids which have a covering of fine waxy powder, 

 ordinary watery applications are of little or no use, 

 and even soap washes or kerosene emulsions must be 

 applied with considerable force and in a fine spray to 

 really wet and be effective. When on cabbage or simi- 

 lar plants arsenical applications are required, the 

 matter becomes even more difficult and some sort of 

 adhesive is needed. Molasses, glucose and soap add 

 materially to the sticking qualities of arsenical sprays 

 other than arsenate of lead; but in extreme cases a 

 resin soap is needed. Such resin soap may be pur- 



