216 Our Friends and how we Treat them . [April, 
why should such tiny pests, animal or vegetable, have be- 
come so much more prominent in our times than in the days 
of our forefathers ? . 
Our first reply must amount to a partial denial ol the 
alleged faCts. Throughout history we can trace the existence 
of blights and mildews, and visitations of locusts, followed 
up in due course of famine. The point of distinction is 
that in our days any new depredator or vastatrix that makes 
its appearance is at once examined, described, and classified 
under a name which is safe not to err on the side of brevity. 
And whilst the savants are thus busy with their microscopes 
the ravages of the pest are duly chronicled in the press, dis- 
cussed on ’Change in a hundred cities, and made the basis 
for speculative operations. 
But there are veritable causes at work rendering it very 
probable that the evils in question may have seriously 
increased. The day of small things is over, whether for 
states, for manufacturing establishments, or for fields. We 
have vast areas of land, formerly occupied with a promis- 
cuous vegetation, now covered with multitudes of one and 
the same species, — vines, coffee-trees, wheat, or potatoes, as 
the case may be. This is not without its meaning. Just 
as we can never have a widespread conflagration in a rural 
district where the houses stand far apart from each other, 
so epidemics do not arise where the species which they 
might attack, animal or vegetable, are few and far between, 
but rage more often and more severely just in proportion as 
such species become numerous and densely concentrated. 
This rule holds good with all classes of destroyers, from the 
jaguar and the wolf to the Doryphora and the Phylloxera, and 
even to those minute organisms which appear to be the 
causes of infectious diseases. They increase with their 
pabulum or their prey. Hence our modern agriculture has 
fostered its own enemies. 
There is still a further cause for the spread of all such 
blights as are occasioned by inseCts. We have interfered 
with the balance of Nature, frequently destroying the very 
species whose especial task seems to be the repression of 
locusts and caterpillars, of gnats and carbuncle-flies ( mouches 
charbonneuses). This task, as naturalists have again and 
again pointed out, though so far with very little effeCt, is 
mainly performed by the small soft-billed birds, — species 
which subsist almost exclusively upon an animal diet. It 
may be taken for granted that just in proportion as a bird 
feeds upon inseCts, rather than upon seeds or fruits, it must 
of necessity be harmless, and even beneficial to man. Yet 
