1910.] Insect Depredations in North America. 51 



destructive to other species of trees. The southern pine 

 beetle (Dendroctonus frontalis, Zimm.) killed a very large 

 percentage of the mature and small pine and spruce trees 

 in 1890-1892 over an area of 75,000 square miles in Virginia, 

 Maryland, Pennsylvania, and North Carolina. Several other 

 bark - boring beetles of the same genus (D. piceaperda, 

 D. engelmanni, D. ponderoscz, D. monticolce, D. brevicomis, 

 and D. pseudotsugce, Hopk.) have also attacked pine timber 

 in different parts of the United States on a very extensive 

 scale. Another prevalent type of insect is the wood-boring 

 beetles, such as the oak timber worm (Eup salts minuta, Dru.), 

 the chestnut timber worm (Lymexylon sericeum, Harr.), and 

 others, which render the wood of living timber defective to 

 such an extent as to reduce the value from 50 to 70 per cent. 



Until about eleven years ago nothing had been done 

 towards preventing this enormous damage. Since then inves- 

 tigations have been conducted by the Bureau of Entomology 

 of the United States Department of Agriculture, and satis- 

 factory progress has been made in ascertaining the principal 

 insect enemies of the forests of North America, in determining 

 their life history, and in devising practical methods of control. 

 In the first instance, a number of the most destructive insects 

 were found to be new to science, while as regards the more 

 important known species little information was available as 

 to their habits, but it is considered that the advice now 

 available would, " if properly utilized for practical applica- 

 tion, evidently prevent from 10 to 30 per cent, of the annual 

 losses at a very small cost." 



The work that has been done is, however, only a beginning, 

 and more purely scientific work on the life history of insects 

 is needed to provide a foundation of facts on which practical 

 recommendations can be based. The need for trained experts 

 is also very strongly urged. 



In addition to remedies based on a knowledge of the habits 

 of the insect or depending on proper forest management, it 

 is possible in many cases to utilize the natural enemies of the 

 insects. 



Dr. Hopkins points out that if it were not for the natural 

 checks and natural factors of control of some of the more 

 destructive insect enemies of forest trees, artificial control 



E 2 



