306 DESTRUCTIVE INSECTS. 



exhaled away. This application will prevent rapid 

 decay, offend the insects, and assist the creation of 

 a new bark over the scar. 



Besides the insects already described as living on 

 the exterior of trees, there are several which are bred 

 in the interior and feed on its living members. The 

 Cerambix gigas inserts her egg in the pith of apple 

 trees, willows, ash, Scotch pine, and even the oak. 

 The maggot eats its way upwards, excavating and 

 subsisting on the material of the pith and wood, 

 leaving behind a hollow passage of not less than 

 one-fourth of an inch in diameter. Before its last 

 transformation it eats a way out of the wood, and 

 reposes in the bark in the pupa state, whence it comes 

 forth a large winged insect. Among sawyers they are 

 called Wurnalls ; and from the size of the trees in 

 which they have been found, and the length of the 

 passage made by them, they must have existed as 

 grubs for several years. How or when the egg is 

 placed in the pith is not known. The damage done 

 to timber after being converted to domestic uses, by 

 boring insects, is too well known to require com- 

 ment. 



