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 “ inerease 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 (Picane 
Sw.) begin by ascending the main trunk; they tra- 
verse it ina 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 
