A slight inferiority in rapidity of flight or in powers of eluding attack might also be a cause of danger to an inedible species of scanty numbers, and in this case too the being merged in another much more abundant species, by similarity of external appearance, would be an advantage.
The question of fact remains.

Do young birds pursue and capture these distasteful butterflies till they have learned by bitter experience what species to avoid?
On this point Dr.Mueller has fortunately been able to obtain some direct evidence, by capturing several Acraeas and Heliconidae which had evidently been seized by birds but had afterwards escaped, as they had pieces torn out of the wing, sometimes symmetrically out of both wings, showing that the insect had been seized when at rest and with the two pairs of wings in contact.

There is, however, a general impression that this knowledge is hereditary, and does not need to be acquired by young birds; in support of which view Mr.Jenner Weir states that his birds always disregarded inedible caterpillars.

When, day by day, he threw into his aviary various larvae, those which were edible were eaten immediately, those which were inedible were no more noticed than if a pebble had been thrown before the birds.
The cases, however, are not strictly comparable.

The birds were not young birds of the first year; and, what is more important, edible larvae have a comparatively simple coloration, being always brown or green and smooth.