The Portland daily press., 1881-06-21
THE PRESS.
Gaudy Butterflies.
How the Gay Insects Do their Counting.
[Pall Mall Gazette. |

[Pall Mall Gazette
1t is not difficult to see that the difference OF
color in the two sides of butterfiy's wings
must be designed for some special purpose, and
that the purpose OF the under side is to escape
detection, while the purpose of the upper side
is to attract attention.
The protective use of the brown under wings
is very simply explained The insect must be
much exposed to birds and other hostile crea-
lures as it sits STILL and so it requires to resem
BILE the grou nd, leaves, or twigs, on which it
usually SO tiles, in order to deceive the eyes of
its enemies. To some people it seems that SO
slight protection as this could scarcely be of
any use to the butterfly. Natural selection,
they say, can hardly work upon such petty diff
ferences. But to talk so is merely to show a
misrepresentation of what natural selection
rightly means. Every butterfly which is
Spotted by bird, and so devoured, is wiped
out of existence forever, with all its possible
progeny. Every butterfly which escapes, by
however slight popularity, is enabled to lay
its eggs in peace and to hand on its peculiari-
ties to its posterity. This sort of selection is
going on every day around u.s. and no differ
ence is too slight for it to select, no resem-
blance is too clumsy provided it once for a mo-
nent aids the insect in avoiding destruction.
Now, we all know that the eyes of birds are
very sharp and keen indeed. A hawk, soaring
SO high in the sky that human sight fails to
perceive it, will yet discriminate and pounce
down upon lark in the fields below-a small
brown bird seated upon brown clod of earth,
exactly like itself in color. In just the same
way the insectivorous birds keep sharp look
out for moths and butterflies, upon which they
swoop at once whenever they distinguish them
upon the ground beneath. Every day those
insects whose color betrays them get thinned
out by their watchful enemies, while those
whose color protects them manage to lay their
eggs in peace and hand on their own peculiar
spots and lines to their descendants. The con-
sequence in the long run is that the butterflies
get better protected from generation to genera
ton, as the chances of interviewing with bad
ly protected individuals are eliminated by the
action of the birds, while only the most imita-
lively colored individuals are left to mate with
one another and to become the parents of fu-
ture swarms. Thus the hostile birds are them
selves the instruments through which the in
sects have been armed defensively against their
depredations. For the various individuals
tend always to vary little in marking-no two
plants or animalsof the same species are ever
exactly alike-but the picking off of the bright
ly colored individuals by the birds, helps to
preserve the protected specific type intact. And
Oh course Cne same causes WHICH now preserve
it originally produced it, Ever since birds and
butterflies have existed the process must con-
stantly have been at work, and the birds and
butterflies themselves in the forms that we
know them are the final outcome OF its perpet-
ual action.
This sufficiently accounts for the initiative
coloring of the under surface, bat it does not
sufficiently account for the brilliant and at
tractive hues of the upper side. Those hues
were probably produced in very different
DC Ar,f rn1
admirals above the hedge yonder engaged in
their pretty rhythmical courtship, flying
round and round one another, now on top
and now beneath, chasing each other in grace
full curves. and seeming to be engaged
for ten minutes at a time in a sort of
aerial quadrille. These two butterflies are
helping in their small degree to keep up and in
{ ensfy the beautiful colors of theirface. They
are coquetting and flirting together, each eager
to display all its charms to the best advantage,
and to attract the other by its own beauty. If
a third and prettier one happens to sail up, the
belle will bestow her affections upon the new
conner, and the vanquished beau will stink
away disgraced, leaving her to her chosen
mate. This second sort of selection is going
on forever, side by side with the first; the
prettiest, freshest, and most daintily marked
insect being always preferred in the pairing
over duller, dingier, or more battered rivals.
1t is interesting to note how the two kinds of
selection run parallel with one another. While
twigs or flowers they are in the greatest dan
ger from birds; but in such positions they close
their wings and display only the outer surface,
which is imitatively and protectively colored.
The constant picking off of all those which
can be distinguished when at rest suffices to
keep the protective colors always true. On
the other hand, when the insects are on the
wing, lowering about flowers or rising in the
air to piroutte and gambol with their mates,
they are too nimble for their pursuers, and
they seem fairly secure by their power of
doubling as they fit rapidly along from spray
to spray The birds are bad marksmen at
moving target; they cannot double like their
prey, and they prefer to aim at their butterflies
sitting, as French sportsmen are said to do at
cartridges. On the other hand, with butter
flies as with men, faint heart never won fair
lady, If the insects did not venture out into
the open to seek their mates and to charm
them with their painted pinions, some holder
rivals would carry off the prize and SO leave
the towards unrepresented in future ages.
Thus, in the course of generations, great
many butterflies have come to have two sets of
colors-the one set attractive for their own
kind and the other set protective against their