THE GENUS DENDKOCTONUS. 
125 
tion in the regular logging operations, should be done between the 
middle of October and the middle of May. 
With this insect it may be practicable to utilize trap trees to at- 
tract the insects away from the healthy timber. For this purpose 
living trees, the necessary number depending on the extent of infesta- 
tion, should be girdled to the heartwood during June. (See fig. 76.) 
If they become infested during the summer they must be barked or 
removed by the middle of the following May, in order to destroy the 
broods. 
BASIS OF INFORMATION. 
The preceding information on the eastern spruce beetle is based on 
investigations by the writer in northwestern Maine in May and June, 
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Fig. 77.— The eastern spruce beetle: Distribution map. (Author's illustration.) 
1900, and at Waterville, N. H., in May, 1903; on experiments with 
girdled trees by Mr. Austin Cary during the summer of 1900, and 
instructions to the Berlin Mills Company, in cutting infested timber, 
in 1901, and on investigations by Mr. W. F. Fiske on Grand Island, 
Michigan, in October, 1906. Additional localities from correspond- 
ence and other collections are West Stewartstown, N. H., Anticosti, 
Canada, and Pennsylvania. 
It is represented in the forest-insect collection of the Bureau of 
Entomology by more than 300 specimens. 
BIBLOGRAPHY. 
Peck, 1876 (under Hylurgus rufipennis), pp. 283-301; Peck, 1879 (under E. rufipen- 
nis), pp. 32-38; Hough, 1882 (Insect Ravages), pp. 259-263; Lintner, 1885 (under 
Dendroctonus rufipennis), p. 54; Fletcher, 1887 (under D. rufipennis), pp. 39-40; Pack- 
