THE SELECTING POWER OF ENEMIES 61 
factors of specific environments: and must 
be powerful selecting agents calling forth 
important corresponding structures. 
One other conclusion that has been arrived at may here 
be mentioned. 
As has been truly pointed out, the welfare of a species 
is almost of as much importance to the species’ enemy as 
to the species itself. In spite of this, some naturalists 
expect to find highly protectively coloured animals almost 
free from enemies. Were this so, then there would be 
no selection, there would be nothing to maintain this 
specialisation, which according to present-day arguments 
would at once begin to degenerate until its efficacy failed, 
permitting the enemy to again destroy. 
It seems, therefore, that the most efficient protective 
coloration can only be maintained by a severe selection 
by enemies. So only can be produced and maintained 
other highly specialised characters such as warning 
coloration. 
One must therefore expect to observe that animals 
which present a high degree of protective or warning 
coloration, frequently form food for their predaceous 
enemies. 
