214 GEOLOGICAL SURVEY OF NEW JERSEY. 



Thousands of oaks in South Jersey, four to eiglit inches in 

 diameter, are " doated " and useless except for short posts or 

 firewood because of the well-meant efforts of woodpeckers to 

 clear the tree of borers. 



In this case the borinq; insect is the larva of the " "-oat moth," 

 Prionoxvstus robinicc, and this makes a galler)- about three- 



Figure 5. — The same stick as Figure 4, cut througli to show the burrow made by larva. The X marks 



indicate where the woodpecker hit the burrow, in each instance 



needing two holes to get a larva. 



sixteenths of an inch in diameter as nearh' as possible in the 

 center of the trunk. ( )ur woodpecker locates this lar\-a with 

 great exactness and drills a hole two to four inches deep, about 

 one and a-half inches scpiare at the surface, and tapering to the 

 diameter of the burrow. In most cases he gets his larva at the 



