is only after the second moult that the ocelli begin to appear, and
these are not fully defined till after the third moult. This progressive
development of the individual--the ontogeny--gives us a clue to the
ancestral development of the whole race--the phylogeny; and we are
enabled to picture to ourselves the very slow and gradual steps by which
the existing perfect adaptation has been brought about. In many larvae
great variability still exists, and in some there are two or more
distinctly-coloured forms--usually a dark and a light or a brown and a
green form. The larva of the humming-bird hawk-moth (Macroglossa
stellatarum) varies in this manner, and Dr. Weismann raised five
varieties from a batch of eggs from one moth. It feeds on species of
bedstraw (Galium verum and G. mollugo), and as the green forms are less
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 In