Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

ILLUS27TATIVE OF NATURAL SELECTION. 137
proportion of the Satyridm and many of the Danaidme are shade-loving butterflies. This question, of
what is to be considered the highest type of any
group of organisms, is one of such general interest to
naturalists that it will be well to consider it a little
further, by a comparison of the Lepidoptera with some
groups of the higher animals.
Mr. Trimen's argument, that the lepidopterous type,
like that of birds, being pre-eminently aerial,~ " therefore a diminution of the ambulatory organs, instead
of being a sign of inferiority, may very possibly indicate a higher, because a more thoroughly aerial
form," is certainly unsound, for it would imply that
the most aerial of birds (tihe swift and the frigatebirds, for example) are the highest in the scale of
bird-organization, and the more so on account of their
feet being very ill adapted for walking. But no ornithologist has ever so classed them, and the claim to
the highest rank among birds is only disputed between three groups, all very far removed from these.
They are —1st. The Falcons, on account of their
general perfection, their rapid flight, their piercing
vision, their perfect feet armed with retractile claws,
the beauty of their forms, and the ease and rapidity of
their motions; 2nd. The Parrots, whose feet, though
ill-fitted for walking, are perfect as prehensile organs,
and which possess large brains with great intelligence,
though but moderate powers of flight; and, 3rd. The
Thrushes or Crows, as typical of the perching birds,
on account of the well-balanced development of their