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NEW YORK STATE MUSEUM 



galleries in other directions from the central chamber. The eggs begin to 

 hatch before the galleries are finished and the grubs burrow in the inner 

 bark on which they feed. The surrounding bark is filled with grubs of 

 various sizes by the time all the eggs are hatched and soon all of the inner 

 part, for a radius of from 2 to 4 inches, is completely honeycombed with 

 burrows. The male guards the entrance in the meantime, and the females 

 either rest in the central chamber or egg gallery, or emerge to make an 

 entrance to the bark in another place and start a new brood. The larvae 

 on attaining their growth enlarge the end of their burrow to form a cell in 

 which they change to the pupa, thence to the adult, and then either 



Fig. 87 Spruce bark rather badly eaten by Fig. 88 Spruce bark badly eaten by 



Polygraphus rufipennis (author's Polygraphus rufipennis 



illustration) (author's illustration) 



emerge from the bark and start a second brood or remain in this retreat 

 till the following spring. 



Dr Hopkins states that two or three broods may occur in one season 

 and that his observations have lead him to believe that owing to the short- 

 ness of the season in the high elevations occupied by the spruce in his 

 State there is generally only one generation. This species, as well as some 

 of its allies, occasionally occurs in swarms since Mrs Slosson records hun- 

 dreds of them in the air at Mt Washington in 1895. 



