<6 



LIBRARY 



RECEl V ED 



* SEP 7' 1927 * 



U. S. Department of Agriwiltaje 



UNITED STATES DEPARTMENT OF AGRICULTURE 



DEPARTMENT BULLETIN No. 1490 



Washington, D. C. 



July, 1927 



DEFECTS IN TIMBER CAUSED BY INSECTS 



By Thomas E. Snyder, Entomologist, Forest Insect Investigations, Bureau of 



Entomology 



CONTENTS 



Page 



Introduction 1 



Types of insect defects ; definitions- 4 



Pinholes 6 



Grub holes 6 



Powder post 7 



Defects classed as pinholes 7 



Pinhole defects formed in living 



trees ; a nonpreventable loss- 10 



Pinholes in living trees 



caused by ambrosia beetles- 10 

 Pinholes in living trees 



caused by timber worms- 14 



Pinhole defects formed in wood 

 after the trees are felled ; a 



preventable loss 15 



Pinholes in felled trees 



caused by ambrosia beetles- 15 

 Pinholes in felled trees 



caused by timber worms- 16 



Pinhole injury to imported logs_ 22 



Defects classed as grub holes or 



wormholes 23 



Grub-hole injury to living trees ; 



a nonpreventable loss 25 



Grub-hole injury to green saw 

 logs and lumber ; a prevent- 

 able loss 26 



Defects classed as powder post 27 



Powder post caused by Lyctus 



beetles 28 



Page 



Defects classed as powder post — Con. 

 Powder post caused by Ptinidae 



and Anobiidae 32 



Powder post caused by Bostrich- 



idae 32 



Powder post caused by round- 

 headed borers (Cerambycidae)_ 33 

 Powder post caused by flat- 

 headed borers (Buprestidae) 34 



Other types of defects 36 



Defects classed as ring distor- 

 tions 36 



Ring distortions caused by 

 defoliation by the bud 



worm 36 



Defects classed as pitch pockets 



and pitchy timber 37 



Defects classed as gum spots or 



streaks 38 



Defects classed as black check- 39 



Defects classed as bluing or 



staining 40 



Defects classed as pith flecks 43 



Pith-fleck injury caused by 



the larvae of flies 43 



Pith-fleck injury caused by 

 the feeding of adult wee- 

 vils 43 



Summary 43 



Literature cited 44 



INTRODUCTION 



It is extremely difficult to estimate the losses due to defects in 

 timber caused by insects. Where the grade of lumber is lowered, 

 the loss may be ascertained by the reduction in the grade, because 

 of the number or size of the holes caused by insects. However, 

 where entire large oak or spruce trees are left to rot in the forest, 



38252°— 27 1 1 



