CONTENTS 



Page. 



PreAT-OUS investigations 5 



Origin of pith flecks 6 



Occlusion of the larval passages 8 



Groups and species of trees affected 9 



Geographic distribution of the cambium miner 10 



Factors affecting local distribution of larv"3e and passages. . 11 



Taxonomic value of pith flecks 12 



Deteriorative effect on quality of wood 12 



References 14 



ILLUSTRATIONS. 



Plate I. Fig. 1 — Transverse section of a branch of river birch, showing pith 

 flecks. Fig. 2 — Tangential section of the trunk of silver maple, 

 showiug pith flecks 



II. Fig. 1 — Transveree section of river birch, showing pith flecks. Fig. 

 2 — Bark of river birch, showing distribution of the mines of larvae. . 



III. Fig. 1 — Transverse section of wild plum, showing three pith flecks. 

 Fig. 2 — Transverse section of service beny, showing one pith fleck. 



I^'. Transverse section of river birch through pith fleck, showing connec- 

 tion between wound tissue and pith rays 



V. Fig. 1 — Radial section of red maple through a pith fleck, showing 

 connection with pith ray. Fig. 2 — Tangential section of river 

 birch through wound tissue of pith fleck at the top 



VI. Transverse section of black cherry, showing two canities caused by 



gunimation of wound tissue 



3 



Page. 



