184 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



Figure 83. — Tunnels in fir made by ambrosia beetles: A, Long winding tunnel 

 made by Platypus wilsoni; branching tunnels made by Gnathotrichus 

 sulcatus. B, adult of Platypus wilsoni X 3. 



ters in the tunnels, each female laying 100 or more. The young 

 larvae wander freely about in the mines, feeding on the ambrosial 

 fungus, and reach maturity in 5 or 6 weeks. When full grown they 

 excavate cells at right angles to the main gallery in which to trans- 

 form to pupae and adults. These cells are parallel to the grain of 

 the wood and are often arranged in groups of 8 to 10 or more. 

 This species is distributed throughout the Pacific coast region and 

 Idaho, where it is the only representative of the family Platy- 

 podidae. 



The wood stainers of the genus Gnathotrichus are small, cylin- 

 drical, dark-brown or black beetles of the size and appearance of 

 a short piece of pencil lead. They attack nearly all species of coni- 

 fers in the Western States, and one species works in alder. Their 

 work is distinguishable from that of other western ambrosia beet- 



