INSECT PESTS 255 



Spray pumps. Many kinds of spray pumps designed to 

 throw liquid upon the plants in minute droplets are for sale 

 by dealers. Sprayers or atomizers quite effective enough for 

 small gardens may be had for as little as fifty cents. Some 

 pumps may be used with an ordinary bucket, and others are 

 carried like a knapsack. For large fields spray pumps drawn 

 by horses are used. In lieu of a spray pump the liquids may 

 be sprinkled on the plants by hand, using a bunch of twigs 

 or a whisk broom for the purpose. 



Other aids in fighting insects. Although insects often mul- 

 tiply prodigiously and may suddenly become exceedingly 

 numerous in a locality, it is seldom that an unusual increase 



FIG. 184. A good form of hand sprayer 



is long maintained. The number of insects averages about 

 the same from year to year. This is doubtless due to the fact 

 that each species has its own natural enemies, and when it 

 becomes abundant, the species that prey upon it also become 

 more numerous and soon reduce it. One of the most powerful 

 of these enemies is the common toad. This animal lives entirely 

 upon insects and is not very particular as to the kind. In the 

 course of a single summer it destroys many thousands of 

 harmful ones. Small snakes also live upon insects and mice, 

 while the usefulness of birds as insect eaters is well known. 

 A large number of the latter, among which are the wood- 

 peckers, swallows, warblers, vireos, and wrens, are entirely 

 insectivorous, while others that eat some seeds make insects 



