THE INSECT WORLD. 



149 



days that subsequently they were not noticeable. If this method 

 cannot for any reason be used, the kerosene emulsion diluted ten 

 times may be appHed, and the vines should be disturbed as the 

 spraying is done. If a Vermorel nozzle is used, it can be held 

 a little distance from the vines and will hit the insects while they 

 are in the air, either jumping or flying. The wetting done in 

 this way is as effective as when done on the leaves, and there is 

 even more chance of hitting them in the air than at rest. So the 

 effort should be to fill the air around the vines, for some little 

 distance, with the fine mist-like spray so easily produced by the 

 Vermorel nozzle. This method should also be made use of if the 

 insects are found in numbers after they are winged. It is appli- 

 cable in many cases, but hardly practical where insects feeding 

 upon wheat or similar plants are to be dealt with. It has been 

 found that the adults are attracted to light, and the electric arc- 

 light, particularly, destroys myriads of them. I have seen in a 

 single globe no less than one pint of leaf-hoppers, and the num- 

 ber included in that measure is almost impossible of estimate. 

 The unfortunate feature in this method is that the damage to 

 vegetation has been done when it takes effect, and it is in the 

 line of preventing injury during the year ensuing, which can 

 be accomplished as readily by the winter treatment. In fact, 

 cleaning up during winter is strongly insisted upon, and will pay 

 many times over. A great number of leaf-hoppers are found in 

 grass lands, where they do much more injury than is generally 

 supposed, — an experiment in Iowa seeming to prove that just 

 about one-half the crop is destroyed in badly infested fields. The 

 experiment was made by setting off two patches of equal size, as 

 nearly equal in all respects as could be made, leaving the one 

 untreated and collecting the leaf-hoppers from the other. Cattle 

 were pastured on both parcels, and that on which the insects 

 were collected supported just double the number. The insects 

 were collected by means of shallow pans coated with tar, drawn 

 by man or horse-power, and in jumping or flying up before it they 

 alighted immediately behind the edge, upon the tar. It requires 

 very few such collections to practically exterminate the pests on 

 a tract of land, but of course the question remains whether it 

 will pay. On grass lands winter treatment is hardly practicable, 

 and collecting in pans is perhaps the only available method. 



