16 
SEASONAL VARIATION 
are both much produced in comparison with those of the wet 
phase, so that it is possible from this character alone to say 
whether a specimen is a dry form or not. 
This has been explained on the ground that dead leaves 
in the dry season are invariably much curled, and the strongly 
accentuated productions of the extremities of the wings 
produce this appearance in the butterflies. J. natalica shows 
differences very similar to the last two species except in one 
particular. J. natalica possesses in the wet form conspicuous 
white spots, which are probably directive marks, i.e. their 
function is to attract the attention of a prospective enemy 
and invite attack on an unimportant part of the structure. 
It is obvious that such spots, which in the wet phase 
probably represent fungoid growths, would interfere con- 
siderably with the resemblance of the dry phase to a dry and 
withered leaf. Accordingly we find that in the full dry phase 
there is no trace of these spots whatever ; but intermediate 
forms are to be met with, in which the spots exist, but they 
have become so diffused and harmonise so beautifully with 
the other dead-leaf markings that they hardly detract at all 
from its protective character. 
There still remain the two most remarkable butterflies 
of the genus from this standpoint. The first of these is 
J. sesamus. The wet phase of this species is a salmon red 
butterfly with a black border marked with white lunules 
and other black spots and markings. The underside is very 
similar to the upper side, except that the ground colour is 
paler and so the black markings are more conspicuous. It is, 
however, much less easily seen than one would think, especially 
when seated on the ground. On the wing it is certainly very 
conspicuous, and there is some reason to believe that, in spite of 
its different shape, it is mimeticafly associated with Acreas 
such as A. acara and A. anemosa, and in some places A. astrigera . 
The dry phase is a very different-looking insect. It is a 
beautiful shade of blue, with darker markings which do not at 
all coincide with the black markings of the wet phase. On 
the underside it is of a dark dusky colour with a distinct green 
shade in it, which is very protective in shady places amongst 
rocks, the favourite resort of this phase. I should have said 
