386 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 



or heartwood until they attain their normal size. They then excavate 

 pupa cells in which to transform into adults, which emerge from the 

 wood through exit holes in the surface. 



This class of borers is represented by a large number of species. 

 The adults, however, are seldom seen by the general observer unless 

 cut out of the wood before they have emerged. Many of them fly at 

 night, while others are so nearly the color of the bark on which they 

 rest that they are difficult to find. The holes made by these borers 

 var} r in size from very minute to more than an inch in diameter, but 

 the intermediate sizes are most common. 



FLAT-HEADED BORERS. 



The work of flat-headed borers is only distinguished from that of 

 the preceding by the broad, shallow burrows and the much more oblong 

 form of the exit holes. In general, the injuries are similar and affect 

 the same class of products, but they are of much less importance. 

 The adult forms are flattened, metallic-colored beetles, and represent 

 many species, of various sizes. 



TIMBER WORMS. 



The character of the work done by the borers of this class is shown 

 in figure 47. The injury consists of pinhole defects in the sapwood 

 and heartwood of felled trees, sawlogs, and like material which have 



a 



FIG. 47. Work of timber worms in oak: a, work of oak timber worm, Eupsaiis minuta; b, barked 

 surface; c, bark; d, sapwood timber worm, Hyloccetus Ingubris, and work; c, sapwood. (Original.) 



been left in the woods or in piles in the open for several months during 

 the warmer seasons. Stave and shingle bolts and closely piled oak 

 lumber and square timbers also suffer from injury of this kind. These 



