ILLUSTRATIONS. 



Plates. 



Page. 



Plate I.— The spruces of Maine . . . 50 



II. — Dendroctonus piceaperda Hopk. .11. sp 52 



III.— Galleries and mines of the spruce-destroying beetles 54 



IV. — Galleries and mines of Dendroctonus piceaperda in spruce 56 



V. — Old galleries of Dendroctonus piceaperda in spruce. . . . 58 



VI. — Spruce bark showing growth of fungus, Polyporus roluatus .... 60 

 VII. — Cocoons of Bracon simplex, a parasite of the spruce-destroying 



beetle _ . 62 



VIII. — Work of secondary and other enemies of spruce ... 64 



IX. — Galleries of Polygraphus rufipennis, showing different stages 66 



X. — Mines of Tetr opium cinnamopterum . . . 68 



XI. — Work of Xyloterus bivittatus ... _ . TO 



XII. — Work of Dendroctonus frontalis and Dendroctonus terebrans 72 



XIII. — Top of Black Spruce infested with a caterpillar and a plant-louse. 74 



XIV.— Dead spruce: also fir and birch . ... 76 



XV.— Timber flooded and killed by water on the Magalloway 78 



XVI. — Sections of wood cut from Balsam Fir showing rapid growth after 



the old spruces die or are felled . 80 



Text Figures. 



Fig. 1. — Diagram illustrating the dormant and active periods of develop- 

 ment of Dendrocton us piceaperda . 19 



2. — Trees girdled by different methods. . .„ 32 



