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THE SCOLYTID BEETLES. 
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Fig. 56.— Work of the Black Hills beetle in the Black Hills National Forest: 4, Small freshly at- 
tacked fine tree, showing pitch tubes. B, Marks of primary galleries on surface of wood when 
bark is removed. C, Freshly attacked tree, showing pitch tubes; near tree not attacked. 
D, Dead tree, showing where outer 1 ar'c lias been removed by woodpeckers. (Author's illus- 
tration.) 
