200 ARTHROPODA 



whitewash containing a repellant chemical is used on tree trunks to 

 drive away the egg-laying adults of borers. The poisonous gases 

 most commonly used as fumigants in insect control are carbon 

 bisulphide, naphthalene, hydrocyanic acid gas, sulphur dioxide, 

 tobacco, formalin and carbon tetrachloride. Young trees are 

 usually fumigated when imported into a state or received from a 

 foreign country. In the orchard, trees are covered with tents and 

 fumigated. 



Temperature Control. — Fall cultivation with reference to the 

 susceptibility of the animal to low temperatures proves beneficial in 

 killing wire worms, potato beetles, tomato worms and grasshoppers. 

 Superheating will kill most of the flour mill insects. The Mediter- 

 ranean fruit fly is limited to a temperature above 50° F., so will 

 probably never get a foothold in any but our Southern States. 



Burning. — As weeds are likely to harbor injurious insects, they 

 should be destroyed. Larvae and adults of garden and orchard 

 pests are burned with the infested brush and vines. 



Natural Enemies. — Sometimes pests are imported into a new 

 territory without the simultaneous introduction of their natural 

 enemies. It is then necessary to find the most important forms that 

 prey upon them. Such has been the province of explorers working 

 for the United States Department of Agriculture. 



Next to the insects themselves, the birds are our most effective 

 insect enemies.^ Some of the most important are the quail, the 

 robin, the cuckoo and the sparrows. Even the despised crow more 

 than pays for the small amount of corn that he eats. Measures 

 that prevent the multiplication of wild races of cats will prove ef- 

 fective in the protection of the birds. 



Other Protective Measures. — Valuable lumber is sometimes 

 stored under water in order to prevent the action of wood borers. 

 The use of fertilizers to stimulate plant growth may hasten develop- 

 ment so that the plant will be able to resist an insect attack. To 

 protect from the tent caterpillar, trees are frequently banded with 

 tar and wrapped in burlap. Crop rotation and early lure crops 

 often rid a plot of potato beetles. Ballou of the U. S. Department 

 of Agriculture discovered (1928) that after a meal of geranium 

 leaves or petals, the Japanese beetle becomes paralyzed. Post- 

 mortems on the 35 per cent of paralyzed beetles which died inside 



® Strickland, E. H. 1928. Can birds hold injurious insects in check? Sc. Men., 

 vol. 26, pp. 48-56. 



