Darwinism (1889): An exposition of the theory of natural selection, with some of its applicationsWallace, Alfred Russel
Science
Darwinism (1889): An exposition of the theory of natural selection, with some of its applications
Wallace, Alfred Russel
Evolution; Natural selection
abundant than the brown, it has probably undergone some recent change of
food-plant or of habits which renders brown the more protective colour.
_Special Protective Colouring of Butterflies._
We will now consider a few cases of special protective colouring in the
perfect butterfly or moth. Mr. Mansel Weale states that in South Africa
there is a great prevalence of white and silvery foliage or bark,
sometimes of dazzling brilliancy, and that many insects and their larvae
have brilliant silvery tints which are protective, among them being
three species of butterflies whose undersides are silvery, and which are
thus effectually protected when at rest.[73] A common African butterfly
(Aterica meleagris) always settles on the ground with closed wings,
which so closely resemble the soil of the district that it can with
difficulty be seen, and the colour varies with the soil in different
localities. Thus specimens from Senegambia were dull brown, the soil
being reddish sand and iron-clay; those from Calabar and Cameroons were
light brown with numerous small white spots, the soil of those countries
being light brown clay with small quartz pebbles; while in other
localities where the colours of the soil were more varied the colours of
the butterfly varied also. Here we have variation in a single species
which has become specialised in certain areas to harmonise with the
colour of the soil.[74]
Many butterflies, in all parts of the world, resemble dead leaves on
their under side, but those in which this form of protection is carried
to the greatest perfection are the species of the Eastern genus Kallima.
In India K. inachis, and in the larger Malay islands K. paralekta, are
very common. They are rather large and showy butterflies, orange and
bluish on the upper side, with a very rapid flight, and frequenting dry
forests. Their habit is to settle always where there is some dead or
decaying foliage, and the shape and colour of the wings (on the under
surface), together with the attitude of the insect, is such as to
produce an absolutely perfect imitation of a dead leaf. This is effected
by the butterfly always settling on a twig, with the short tail of the
hind wings just touching it and forming the leaf-stalk. From this a dark
curved line runs across to the elongated tip of the upper wings,
imitating the midrib, on both sides of which are oblique lines, formed
partly by the nervures and partly by markings, which give the effect of
the usual veining of a leaf. The head and antennae fit exactly between
the closed upper wings so as not to interfere with the outline, which
has just that amount of irregular curvature that is seen in dry and
withered leaves. The colour is very remarkable for its extreme amount of
variability, from deep reddish-brown to olive or pale yellow, hardly two
specimens being exactly alike, but all coming within the range of colour
of leaves in various stages of decay. Still more curious is the fact
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