i (, exci} 
quite irrespective of the ribbing the granules being 
greyish. 
Pentila muhata is brown under direct or transmitted lights 
in its brown areas, and with the upper chitine re- 
moved reveals a dense granulation of darker brown. 
The whitish areas are the same in both lights, but 
on removing the upper wall the surface is finely 
granulated with almost transparent globules. 
Pentila undularis is quite white but becomes yellowish trans- 
parent white under transmitted light; with the 
ribbed upper wall removed the scale is coarsely 
granulated, the granules being transparent, except 
on their circumference which is greyish. Under 
direct light the scale is quite invisible as an opaque 
object, when the ribbed surface is gone. 
Oberonia ornatus is pure white, but under transmitted 
light becomes hyaline dirty straw colour; with the 
upper ribbed wall removed the interior is seen to 
be very finely granulated with transparent greyish 
granules. 
The tawny red species of the genus Jiptena are almost the 
same colour under both lights. 
These investigations lead me to believe that blue pigment 
does not exist, but that though in some cases the scales appear 
to be quite colourless, yet in the great majority of cases blue 
colour seems to require a basis of yellow for its production 
by diffraction. In all the species that I have examined 
there is an under layer of brownish scales below the blue ones, 
which doubtless absorb unneeded light and in the case of the 
colourless scales probably assist the colour in some method. 
The case of the metallic greens is less conclusive inasmuch 
as Ornithoptera brookeana may prove to have a subcutaneous 
colouring matter; but apart from that there appears to be 
no evidence so far as the Rhopalocera are concerned that there 
is green pigment present, nearly all the greens requiring a basis 
of pink to red whilst the strongly metallic and refulgent greens 
appear to require a basis of violet or lilac for their production. 
The whites have also very rarely white pigment, and are 
