21 7
view. Consequently there is no universal instinctive shrink
ing from conspicuous colour on the part of the enemy.
It is false to say that certain disabilities will not deter
from attack apart from warning colours. It is not certain
that if an insect were attacked and rejected that it would
therefore perish. It is not true that certain disabilities as
sociated with conspicuous colours deter from attack. How
far the animals so endowed are liable to attack depends
upon the pressure of necessity due to hunger or to skill
in overcoming disabilities on the part of the insect-eater.
Nor is the explanation of the way in which warning
colours have been produced by Natural Selection more
satisfactory. Starting with an edible species which has
not a particularly conspicuous colouring, it is assumed
that there is first an evolution of a nauseous taste or
other disability, and secondly an evolution of warning
colours. Mr. Wallace gives two different explanations of
the way in which a nauseous taste was developed. In
his Tropical Nature, he speaks of the time when “ the
Danaidae first began to acquire those nauseous secretions,
which are their protection in the early stages of their
development ” ; and then of another time when they be
came decidedly unpalatable.* In his Darwinism, he says,
“ The Heliconidae first arose from some ancestral species
or group which, owing to the food of the larvie or some
other cause, possessed disagreeable juices that caused them
to be disliked by the usual enemies of their kind.”j-
If the nauseous taste were the result of the direct action
of the adoption of some new food-plant, one of two results
would follow. Either the enemy would leave the insect
severely alone, having plenty of other food to resort to ;
and then, in the absence of any interposition on the part
p. 190.
t p. 243.