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 

 Heliconidse, 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 



