80 MIMICRY, AND OTHER PROTECTIVE 
their under surfaces. This property places them some- 
what in the position of those curious wingless birds of 
oceanic islands, the dodo, the apteryx, and the moas, 
which are with great reason supposed to have lost the 
power of flight on account of the absence of carnivorous 
quadrupeds. Our butterflies have been protected in a 
different way, but quite as effectually ; and the result 
has been that as there has been nothing to escape from, 
there has been no weeding out of slow flyers, and as 
there has been nothing to hide from, there has been no 
extermination of the bright-coloured varieties, and no 
preservation of such as tended to assimilate with sur- 
rounding objects. 
Now let us consider how this kind of protection must 
act. Tropical insectivorous birds very frequently sit on 
dead branches of a lofty tree, or on those which overhang 
forest paths, gazing intently around, and darting off at 
intervals to seize an insect at a considerable distance, 
which they generally return to their station to devour. 
If a bird began by capturing the slow-flying, conspicuous 
Heliconidz, and found them always so disagreeable that 
it could not eat them, it would after a very few trials 
leave off catching them at all; and their whole appear- 
ance, form, colouring, and mode of flight is so peculiar, 
that there can be little doubt birds would soon learn to 
distinguish them at a long distance, and never waste 
any time in pursuit of them. Under these circumstances, 
_ it is evident that any other butterfly of a group which 
birds were accustomed to, devour, would be almost 
equally well protected by closely resembling a Heliconia 
