310 INSECTS AFFECTING VEGETATION 



certain years it has killed a large amount of timber. Records of ex- 

 tensive destruction of timber in the Southern States are found dating 

 back to the early part of the nineteenth century. This species may 

 be considered one of the most dangerous insect enemies of southeast- 

 ern conifers and, therefore, a constant menace to the pine forests of 

 the Southern States. 



The Eastern Spruce Beetle. During the period between 1818 

 and 1900 there were several outbreaks of the eastern spruce beetle 

 in the spruce forests of New York, New England, and southeastern 

 Canada. This species caused the death of a very large percentage of 

 the mature spruce over an area of thousands of .square miles. In 

 the aggregate many billions of feet of the best timber were de- 

 stroyed. The larger areas of this dead timber furnished fuel for 

 devastating forest fires, with the result that in most cases there was 

 a total loss. 



The Engelmann Spruce Beetle. Another barkbeetle, similar 

 in habits to the Eastern spruce beetle, has from time to time during 

 the past fifty years caused widespread devastations in the Rocky 

 Mountains region to forests of Engelmann spruce, in some sections 

 killing from 75 to 90 per cent of the timber of merchantable size. 



The Black Hills Beetle. One of the most striking examples of 

 the destructive powers of an insect enemy of forest trees is found in 

 the Black Hills National Forest of South Dakota, where during the 

 past ten years a large percentage of the merchantable timber of the 

 entire forest has been killed by the Black Hills beetle. It is esti- 

 mated that more than a billion feet of timber have been destroyed 

 in this forest as the direct result of the work of this beetle. This de- 

 structive enemy of the western pine is distributed throughout the 

 forests of the middle and southern Rocky Mountains region, where, 

 within recent years, it has been found that in areas of greater or less 

 extent from 10 to 80 per cent of the trees have been killed by it. 



The Mountain Pine Beetle and the Western Pine Beetle. The 

 sugar pine, silver pine, western yellow pine, and lodgepole pine of the 

 region north of Colorado and Utah, westward to the Cascades, and 

 southward through the Sierra Nevadas are attacked by the mountain 

 pine beetle and the western pine beetle, and, as a direct consequence, 

 billions of feet of the timber have died. In one locality in northeast- 

 ern Oregon it is estimated that 90 to 95 per cent of the timber in a 

 dense stand of lodgepole pine covering an area of 100,000 acres has 

 been killed within the past three years by the mountain pine beetle. 

 Throughout the sugar-pine districts of Oregon and California, as 

 the result of attacks by this same destructive barkbeetle, a consider- 

 able percentage of the largest and best trees is dead. 



The Douglas Fir Beetle. The Douglas fir throughout the re- 

 gion of the Rocky Mountains from southern New Mexico to British 

 Columbia has suffered severely from the ravages of the Douglas fir 

 beetle, with the result that a large percentage of dead timber is 

 found, much of which will be a total loss. Three other species of 

 beetles, having destructive habits similar to those above mentioned, 

 depredate on the pines of New Mexico and Arizona, and still another 



