ENEMIES OF PLANTS. ;507 



IX. Study on Spraying. 



EXERCISE 13 (a) From the formulas given, compute 

 the amount of each material required to make one-half 

 gallon of some one arsenical spray as, Paris green and 

 one of the contact insecticides as, kerosene emulsion 

 and carefully prepare each. 



(&) Spray some plants infested with caterpillars or 

 slugs as, the tomato-worm or the rose-slug, and other 

 plants infested with plant-lice with each of these insec- 

 ticides prepared, and watch results. 



(c) To be absolutely sure of these results, place a por- 

 tion of the plants infested by each of -these insects ex- 

 perimented upon in each of two breeding-jars, placing 

 that portion sprayed with Paris green in one jar and 

 that sprayed with kerosene emulsion in the other. 

 Label each, and note the effect of each spray upon each 

 kind of insect. 



(d) Did the Paris green affect all of them in the same 

 way? Examine the mouth-parts of each insect experi- 

 mented upon and explain the action of the poison. 



(e) Did the kerosene affect all alike ? Explain. 



X. Natural Enemies. 



Among the natural enemies of insects are 

 birds, predaceous ^ insects, toads, spiders, etc. 

 Few persons realize the extent of the work 

 done by these natural enemies in exterminating 

 noxious insects. Particularly is this true of the 

 birds and predaceous insects. 



i. T/ie Birds to which we so begrudge our 

 fruit and grain are more than compensating us 

 for this loss by keeping in check insects that 

 would otherwise increase with such rapidity as 

 to endanger the entire crop of orchard or field. 



