be attacked by their enemies when at rest; and most kinds whilst
resting raise their wings vertically over their backs, so that the
lower surface alone is exposed to view. Hence it is this side which is
often coloured so as to imitate the objects on which these insects
commonly rest. Dr. Rossler, I believe, first noticed the similarity of
the closed wings of certain Vanessae and other butterflies to the bark
of trees. Many analogous and striking facts could be given. The most
interesting one is that recorded by Mr. Wallace (7. See the interesting
article in the Westminster Review, July 1867, p. 10. A woodcut of the
Kallima is given by Mr. Wallace in Hardwicke s Science Gossip,
September 1867, p. 196.) of a common Indian and Sumatran butterfly
(Kallima) which disappears like magic when it settles on a bush; for it
hides its head and antennae between its closed wings, which, in form,
colour and veining, cannot be distinguished from a withered leaf with
its footstalk. In some other cases the lower surfaces of the wings are
brilliantly coloured, and yet are protective; thus in Thecla rubi the
wings when closed are of an emerald green, and resemble the young
leaves of the bramble, on which in spring this butterfly may often be
seen seated. It is also remarkable that in very many species in which
the sexes differ greatly in colour on their upper surface, the lower
surface is closely similar or identical in both sexes, and serves as a
protection. (8. Mr. G. Fraser, in Nature, April 1871, p. 489.)
Although the obscure tints both of the upper and under sides of many
butterflies no doubt serve to conceal them, yet we cannot extend this
view to the brilliant and conspicuous colours on the upper surface of
such species as our admiral and peacock Vanessae, our white
cabbage-butterflies (Pieris), or the great swallow-tail Papilio which
haunts the open fens for these butterflies are thus rendered visible to
every living creature. In these species both sexes are alike; but in
the common brimstone butterfly (Gonepteryx rhamni), the male is of an
intense yellow, whilst the female is much paler; and in the orange-tip
(Anthocharis cardamines) the males alone have their wings tipped with
bright orange. Both the males and females in these cases are
conspicuous, and it is not credible that their difference in colour
should stand in any relation to ordinary protection. Prof. Weismann
remarks (9. Einfluss der Isolirung auf die Artbildung, 1872, p. 58.),
that the female of one of the Lycaenae expands her brown wings when she
settles on the ground, and is then almost invisible; the male, on the
other hand, as if aware of the danger incurred from the bright blue of
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