ON COLOURS IN NATURE. 87 
become faded and bleached. ''o a certain extent the colouring 
of butterflies, as well as their size, shape, and markings, 
indicates the particular tribe to which they belong,—e.g., the 
blue of many of the Morphide, the yellow of the Ornithoptera, 
the bright and various tints of the Catagrammas are peculiar 
to themselves, and have no parallel among other genera of 
butterflies. On the other hand, there is such a similarity 
between some species of Papilio and those of Huploea, between 
one particular Diadema and a species of Danais, between the 
genus Kuryphene and that of Romalaosoma, as a whole, that 
the distinctions must be sought for in the nervation of the 
wings, or in some other structural divergence, and not in the 
respective outward colouring merely. 
The survey of an Oriental crowd gathered together on some 
public occasion, as the setting forth or return of a procession, 
when all the spectators attired in flowing robes have donned 
their best dresses to view the sight, will inevitably lead to 
the conclusion that blue is the Hastern’s favourite colour, and 
worn far more extensively than orange, black, or white. The 
blue in question is obtained by steeping the garments in vats 
of indigo dye, such as may be seen at the doors of the clay- 
built huts of Keneh, Upper Egypt, and the garments so 
stained are then suspended on cords across the narrow street 
to dry. Now, there must be some prompting of a picturesque 
effect that has led the Oriental to the adoption of this colour,— 
possibly the contrast between it and the green palm-trees and 
yellow sand that form his every-day surroundings in so many 
places,—as his preference for it is manifestly not confined to 
articles of dress, but window-shutters, door-posts, palisades, 
&c., are similarly painted, and thus afford additional evidence 
of his taste in this particular. 
With regard to the question how far the colour of insects 
is caused or modified by outward circumstances, | have had to 
apply for information to those who have made these and such- 
like matters their special study, and am credibly informed 
that the larvee of certain species can be modified by varying 
surroundings, and the pupae also, but independently ; in 
other words, I conclude that we are to understand that both 
caterpillars and chrysalids can have their colours altered or 
modified by external causes, but that the chrysalids do not 
derive their altered tint from the caterpillar stage, but 
undergo a separate modification in their turn; also in no 
case does the effect go on into the next stage, or make any 
difference to the imago (as far as work has gone at present). 
Only in one case does larval dimorphism (green and brown) 
