28 



BULLETIN 1490, U. S. DEPARTMENT OF AGRICULTURE 



heart wood of both hardwoods and softwoods, from which the powder 

 will fall when moved or jarred. 22 The interior is honeycombed by 

 irregular burrows made by the larvae and when badly damaged is 

 converted into a mass of closely packed material, which readily 

 crumbles into fine flourlike powder or coarser pellets of excreted 

 wood. This is held together by an outer thin shell and intervening 



fibers of soimd wood. 

 These defects will be 

 discussed in the order 

 of the size of the holes 

 caused by the various 

 types of insects. All 

 powder-post damage 

 can be prevented. 



POWDER POST CAUSED BY 

 LYCTUS BEETLES 



The in j ury caused 

 by Lyctus beetles is 

 confined to the white- 

 wood or sapwood of 

 hardwoods ($4). It 

 consists of small holes 

 one-sixteenth to one- 

 twelfth of an inch in 

 diameter, with irregu- 

 lar burrows filled with 

 flourlike powder. Air- 

 dry or kiln-dry sap- 

 wood material, and 

 sapwood which has 

 been stored or piled 

 in one place for two. 

 three, or more years, 

 especially second- 

 growth ash, hickory, 

 and oak, are princi- 

 pally affected; but other hardwoods, such as walnut, maple, persim- 

 mon, cherry, elm, poplar, and sycamore, are also damaged. 



Seasoned shipbuilding and airplane lumber and gunstock blanks, 

 stored in large quantities, and finished stores, such as wheelbarrows, 

 tent poles, oars, airplane parts, shovel and pick handles, and many 

 other hardwood articles used in the military services are subject to 

 serious damage by powder-post beetles. (Fig. 28.) 



Hickory, ash, and oak furniture, interior woodwork of buildings 

 (fig. 29), and the woodwork of farming machinery and implement 

 handles; ladder stock, such as rungs; vehicle stock, such as hubs, 

 spokes, felloes, rims, singletrees, poles, and shafts: and cooperage 

 stock (barrel-stave bolts) are also injured. 



Fig. 30. 



-Powder-post defect in pine made by 

 ■peltatus 



Xyli 



— Insects which have this peculiar habit of reducing wood fiber to a powderlike con- 

 dition belong chiefly to the families Lyctidae, Ptinidae, Anobiidae, Bostricbidae, and 

 Cerambycidae. By far the larger part of the injury is caused by species of the genera 

 Lyctus and Neoclytus. 



