AMERICAN ECONOMIC ENTOMOLOGY 221 



gardens, orchards, and greenhouses are literally devastated. 

 Almost all kinds of garden and field crops — not even excluding 

 tobacco — were attacked by the "army" of 1899. Investigation 

 showed that this species, again unlike the true army-worm, 

 usually reappears in scarcely diminished numbers in the year 

 following a great visitation. Drastic measures are therefore 

 necessary, and poisoning by arsenic or kerosene has accordingly 

 been recommended as the most effectual means of destroying its 

 legions. 



The mention of tobacco in the preceding paragraph recalls 

 the fact that the cultivation of this narcotic constitutes an 

 important industry in parts of the United States. Although 

 indigenous, tobacco (perhaps on account of its essential con- 

 stituent) is much less subject to the attacks of insects than are 

 many other native American plants, and has no insect pests 

 peculiarly its own ; nevertheless, a certain amount of damage 

 is yearly inflicted on this crop by insects, and occasionally 

 the injury becomes serious. Several remedies have been 

 suggested, such as poisoning the seed-beds and spraying the 

 plants themselves with arsenic. Still better, perhaps, is the 

 expedient of growing patches of other solanaceous plants, such 

 as datura, horse-nettle, and nightshade, which will attract the 

 insects while the tobacco is still young, and can subsequently 

 be cut down and destroyed with their infesting parasites. 



As an example of the excellent work accomplished by the 

 Bureau in helping to save the remnant of the magnificent 

 timber forests of the United States from destruction by insects, 

 the case may be cited of the Black Hills beetle (Dendroctonus 

 ponderosus), a lamellicorn species which drives dendritic tunnels 

 under the bark of pine-trees very similar to those made by an 

 English species in elm timber. This mischievous beetle, which 

 measures about a quarter of an inch in length, ranges through 

 the eastern sections of the Rocky Mountain district from the 

 Black Hills in South Dakota to New Mexico, while to the west- 

 ward it enters Arizona and Utah. 



Four species of valuable pines and spruces are attacked and 

 killed by this beetle, which is estimated to have destroyed 

 between 700 millions and one billion cubic feet of timber in the 

 Black Hills Forest Reserve alone, while it has done incalculable 

 damage in Colorado and New Mexico. 



Without particularising the methods which have been 



