186 Evolution and Adaptation 
wooing ; and in this case we can understand how it is that 
they have been rendered the more beautiful.” 
A most significant fact in connection with the difference 
in sexual coloration of butterflies did not escape Darwin’s 
attention. 
“Whilst reflecting on the beauty of many butterflies, it 
occurred tome that some caterpillars were splendidly colored ; 
and as sexual selection could not possibly have here acted, it 
appeared rash to attribute the beauty of the mature insect to 
this agency, unless the bright colors of their larvee could be 
somehow explained. In’ the first place, it may be observed 
that the colors of caterpillars do not stand in any close corre- 
lation with those of the mature insect. Secondly, their bright 
colors do not serve in any ordinary manner as ‘a protection. 
Mr. Bates informs me, as an instance of this, that:the most 
conspicuous caterpillar which he ever beheld (that of a 
Sphinx) lived on the large green leaves of a tree on the open 
llanos of South America; it was about four inches in length, 
transversely banded with black and yellow, and with its head, 
legs, and tail of a bright red. Hence it caught the eye of any 
one who passed by, even at the distance of many yards, and 
no doubt that of every passing bird.” 
Darwin applied to Wallace for a solution of this difficulty, 
and received the reply that he “thought it probable that con- 
spicuously colored caterpillars were protected by having a 
nauseous taste; but as their skin is extremely tender, and as 
their intestines readily protrude from a wound, a slight peck 
from the beak of a bird would be as fatal to them as if they 
had been devoured. Hence, as Mr. Wallace remarks, ‘dis- 
tastefulness alone would be insufficient to protect a caterpillar 
unless some outward sign indicated to its would-be destroyer 
that its prey was a disgusting morsel.’ Under these circum- 
stances it would be highly advantageous to a caterpillar to be 
instantaneously and certainly recognized as unpalatable by all 
birds and other animals. Thus the most gaudy colors would 
