176 STUDY OF NATURAL HISTORY. 



tirely of insects. To illustrate this, even in a very 

 confined compass, let us still fancy the tree we have 

 just spoken of, bearing in itself a living world of 

 insects, yet flourishing in beauty and luxuriance. 

 We might imagine that the innumerable artifices 

 by which these little creatures are taught to guard 

 themselves, would effectually protect them from 

 their enemies ; and that, so secured, they would go 

 on to " increase and multiply" with that rapidity 

 which naturally results from security. But what 

 would then be the inevitable consequence ? Cer- 

 tainly the death of the tree, by which the whole 

 are fed ! for if these devourers of leaves, of flowers, 

 of fruits, of bark, and of sap, were doubled or 

 trebled, which they very soon would be, both tree 

 and insects would perish together. Now, that this 

 general destruction should not happen, but that the 

 lives of another class of animals should be supported 

 by the superabundance of the insects, birds are 

 called into being, and are appointed to fulfil their 

 repective parts in the wonderful economy of nature. 

 Let us, then, look to those tribes who would frequent 

 this same tree for the purpose of seeking food ; and 

 who would thus, by so doing, prevent the catastrophe 

 we have just supposed. The woodpeckers (Piciana 

 Sw.) begin by ascending the main trunk ; they tra- 

 verse it in a spiral direction, and diligently examine 

 the bark as they ascend ; wherever they discern the 

 least external indication of that decay produced by 

 the perforating insects (generally the grubs of 

 beetles), they commence a vigorous attack: with 

 repeated strokes of their powerful wedge-shaped 

 bill, they soon break away the shelter of the internal 



