39 



Its boring-dust, seen in white piles in the crevices below the entrance- 

 holes, is in the form of minute splinters of wood, and quite easily distinguished 

 from the meal-like boring-dust of Gnathotrichus. 



The adult beetle is about five millimetres (one-fifth of an inch) in leigth, 

 dark brown in colour, flattened, elongate, with the wing-covers strongly ribbed, 

 and, in the male, produced on each side behind. 



ECONOMIC IMPORTANCE OF THE AMBROSIA-BEETLES. A considerable 

 amount of injury is caused by these "pin-hole" borers, and they are likely to 

 become more numerous in the future, as cutting becomes more extensive. They 

 breed in all dying trunks, and recently cut logs and stumps; never ia dead and 

 dry wood, and seldom, perhaps never, in perfectly healthy trees. The Pacific 

 Coast Timber-beetle is the most injurious, since its tunnels penetrate several 

 inches deeper into the wood. Such injury is chiefly to logs which remain out of the 

 water during summer. The timber-beetles are particularly injurious in the 

 west to fire-injured timber, and about recent burns the little piles of white 

 boring dust, extruded from their tunnels, are spotted over even the thoroughly 

 blackened bases. The inner bark and wood of these trees are of course still 

 full of sap, and entrance is made through cracks in the burned surface of the 

 bark. 



CONTROL MEASURES. 



These insects enter dying trunks and logs in which the inner bark and 

 sap-wood are green and full of fermenting sap, or even barked logs and sawn 

 lumber, if the surface is moist; but never through a dry, sapless wood surface. 

 They start their tunnels during the spring and summer months, so that logs 

 cut between April and September are often attacked shortly after being felled. 

 The late fall and winter cut usually remains sappy until spring and is then 

 readily attacked. Logs cut in the early fall are not entered that season, and if 

 piled loosely in the open often dry sufficiently to be protected from attack the 

 following spring. Logs placed in water are safe from further serious injury. 

 There is little injury when the summer cut is placed in water as rapidly as 

 produced and the winter cut floated before the middle of April. Lumber from 

 summer sawing of green logs is partially protected by piling loosely so that 

 the surface dries rapidly. 



THE LARGER WOOD-BORERS. 



In localities where logs are, for any reason, left out of water in the limits 

 for two or more seasons, serious damage often results from the work of large 

 wood-boring larvae of the families Cerambycidce and Buprestidce, As these are 

 to be dealt with in a later publication, only a brief reference to the injury is 

 included here. The adults are medium to large beetles; the Cerambycidce, 

 Round-headed Borers, or Long-horned Beetles, with long antennae or feelers; 

 the Buprestidce often with metallic colouration and therefore known as The 

 Metallic Wood-borers, and also as Flat-headed Borers. 



The adults pair during summer, and the females insert their eggs in slits 

 in the bark cut with the jaws or mandibles, or place them in bark crevices. 

 The mating adults are often seen in great numbers on logs and slash or fire- 

 injured timber, crawling upon the bark and flying readily when disturbed. 

 The grubs feed for a few weeks upon the inner bark, and later many species 

 enter the wood beneath, where they live for one or two years, or in some cases 

 longer. Some species bore only in the outer part of the sap-wood; other more 

 injurious species drive their tunnels throughout the sap-wood deep into the 

 heart-wood. Their large tunnels, one-half inch in diameter or smaller, destroy 

 the wood for all valuable purposes. 



