392 
SEXUAL SELECTION. 
Pakt II. 
as we can judge, either for protection or as an attraction 
between the sexes. With many species of butterflies 
the upper surfaces of the wings are obscurely coloured, 
and this in all probability leads to their escaping ob- 
servation and danger. But butterflies when at rest 
would bo particularly liable to be attacked by their 
enemies; and almost all the kinds when resting raise 
their wings vertically over their backs, so that the lower 
sides alone are exposed to view. Hence it is this side 
which in many cases is obviously coloured so as to 
imitate the surfaces on which these insects commonly 
rest. Dr. Rossler, I believe, first noticed the similarity 
of the closed wings of certain Van ess* and other butter- 
flies to the bark of trees. Many analogous and striking 
facts could be given. The most interesting one is that 
recorded by Mr. Wallace 5 of a common Indian and 
Sumatran butterfly (Kallima), which disappears like 
magic when it settles in a bush ; for it hides its head 
and antennae between its closed wings, and these in 
form, colour, and veining cannot be distinguished from 
a withered leaf together with the 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 re- 
semble the young leaves of the bramble, on which this 
butterfly in the spring may often be seen seated. 
Although the obscure tints of the upper or under 
surface of many butterflies no doubt serve to conceal 
them, yet we cannot possibly extend this view to 
the brilliant and conspicuous colours of many kinds, 
such as our admiral and peacock Vanessas, our white 
Sec the interesting article in the < Westminster Review,’ Julv, 1867, 
p. 10. A woodcut of the Kallima is given by Mr. Wallace in Hard- 
wieke’s ‘ Science Gossip,’ Sept. 1867, p. 196. 
