USE OF WOODPECKERS. 297 



forests, by clearing the trees of many of the insects 

 that are the most destructive to timber. The most 

 injurious of these, are those that mine the cambium 

 when it is in the soft and pulpy state ; and as they 

 work for a long way under the bark, without any im- 

 mediate external indication of their presence and con- 

 duct, they could not be removed by any birds that were 

 not gifted with rhabdomancy, like the woodpecker, 

 and, at the same time, more expert in running than 

 themselves. Those insects are destructive to almost 

 every kind of tree, and it is by no means improbable 

 that, as is the case with regard to aphides, every 

 species of tree may have its peculiar enemy. Even the 

 most austere juices are no protection against the depre- 

 dations of these hidden plunderers. The turpentine of 

 pines is, when fully matured, very offensive to the ge- 

 nerality of insects ; but not so the cambium and the 

 buds. There is a cynips (we know not the species 

 exactly,) that punctures the latter, especially where 

 the growth is stunted, and the soil too light, or the 

 exposure too hot for the tree ; and as its brood are 

 hatched, they send out the whole substance of the tree, 

 not only the part that is pushed forward to expand the 

 new shoots, but that which would form the wood and 

 bark, in an efflorescence, as if the trees were powdered 

 with lime. In consequence of that, the tree, though it 

 does not die, increases no more in size ; and there are 

 places where pines have remained in that quiescent 

 state for many years. That insect, however, attacks the 

 trees chiefly when they are young, and therefore there 

 is no farther loss than the few years that the trees have 

 stood ; and when they have shown the disease very 



