The Making of Species 
themselves, but rest on the upper surfaces of 
leaves and flowers. Moreover, they all have 
juices which exhale a powerful scent; so that, if 
they are killed by pinching the body, a liquid 
exudes which stains the fingers yellow, and leaves 
an odour which can only be removed by re- 
peated washing. This odour is not very offen- 
sive to man, but has been shown by experi- 
ment to be so to birds and other insect-eating 
animals. 
“Warning colours are advertisements, often 
highly coloured advertisements, of unsuitability 
as food. Insects are of two kinds—those which 
are extremely difficult to find, and those which 
are rendered prominent through startling colours 
and conspicuous attitudes. Warning colours 
may usually be distinguished by being con- 
spicuously exposed when the animal is at rest. 
Crude patterns and startling contrasts in colour 
are characteristically warning, and these colours 
and patterns often resemble each other; black 
combined with white, yellow, or red, are the 
commonest combinations, and the patterns usually 
consist of rings, stripes, or spots.” 
We trust that we shall be forgiven for this 
lengthy quotation. Our object in reproducing so 
large an extract is to allow the Neo-Darwinians 
to speak for themselves. Were we to state their 
theory in our own words, we might perhaps be 
charged with stating it inaccurately. We should 
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