iquity, since a few small deposits, believed to be of
Miocene age, have been found on them, but there can be little doubt that
their present fauna, at all events as concerns the birds, had its origin
since the date of the last glacial epoch. Even now icebergs reach the
latitude of the Azores but a little to the west of them; and when we
consider the proofs of extensive ice-action in North America and Europe, we
can hardly doubt that these islands were at that time surrounded with
pack-ice, while their own mountains, reaching 7,600 feet high in Pico,
would almost certainly have been covered with perpetual snow and have sent
down glaciers to the sea. They might then have had a climate almost as bad
as that now endured by the Prince Edward Islands in the southern
hemisphere, nearly ten degrees farther from the equator, where there are no
land-birds whatever, although the distance from Africa is not much greater
than that of the Azores from Europe, while the vegetation is limited to a
few alpine plants and mosses. This recent origin of the {253} birds
accounts in a great measure for their identity with those of Europe,
because, whatever change has occurred must have been effected in the
islands themselves, and in a time limited to that which has elapsed since
the glacial epoch passed away.

_Insects of the Azores._--Having thus found no difficulty in accounting for
the peculiarities presented by the birds of these islands, we have only to
see how far the same general principles will apply to the insects and
land-shells. The butterflies, moths, and hymenoptera, are few in number,
and almost all seem to be common European species, whose presence is
explained by the same causes as those which have introduced the birds.
Beetles, however, are more numerous, and have been better studied, and
these present some features of interest. The total number of species yet
known is 212, of which 175 are European; but out of these 101 are believed
to have been introduced by human agency, leaving seventy-four really
indigenous. Twenty-three of these indigenous species are not found in any
of the other Atlantic islands, showing that they have been introduced
directly from Europe by causes which have acted more powerfully here than
farther south. Besides these there are thirty-six species not found in
Europe, of which nineteen are natives of Madeira or the Canaries, three are
American, and fourteen are altogether peculiar to the Azores. These la