VARIATIONS IN THE COLOUR OF LEPIDOPTERA. 173 
and in some cases nearly white. Specimens are occasionally 
found suffused almost entirely with black, and the relative 
proportions of the colours varies considerably. It would be 
impossible to say what is the normal colour in this species. 
I find that in the Outer Hebrides and in the Island of Arran 
the coloration is much more uniform, the general appearance of 
all the specimens being greyish. C. immanata varies in a similar 
manner, except that only in the Shetlandic specimens have I seen 
any tendency to red in the centre of the wing. Peronea cristana 
varies from almost black to nearly white, and the tufts in the 
wings vary in colour from black to red, yellow, or white. The 
same difference also obtains in the shoulder markings, and in the 
dashes on the inner edges of the wings. Several others of the 
Peronea differ in an equally remarkable manner amongst them- 
selves, whilst one species, on the other hand, is very constant in 
colour in this country. 
TopomorpPHisM.—I place under this class all local variations. 
These may be sufficiently constant as to admit of being considered 
subspecific or racial ; and in certain districts the variation appears 
to take place in response to the geological environment. In the 
British Isles the most remarkable topomorphic variation is that 
of Hepialus humuli. This species which, so far as I am aware 
of, in England and Scotland has a silvery coloured male, and a buff 
female with a few reddish markings; but in the Shetland Isles it 
appears to be subject to many variations, the colouring of the 
sexes being reversed, both in the case of males and females, and 
some varieties being more melanic; so that the Hepialus humuli 
of those islands has been raised to a subspecific rank, Hethlandica, 
by Staudinger; and as well as being topomorphic is also truly 
polymorphic. In the Outer Hebrides Boarnuia repandata departs 
from the normal coloration of that species as found in England, 
viz., various shades of brown, to a prevailing slaty grey, with 
darker markings. To this well-defined topomorphic variation I 
have ventured to give the name of Sodorensium. As an instance 
of a topomorphic variety dependent apparently on the geological 
environment, I know of no better example than that of Gnophos 
obscuraria. This insect on the chalk downs, near Lewes, is found 
almost white with dark markings, and of a light grey ground 
colour with darker markings; but on the peaty soil of the New 
Forest I have taken it in plenty of a very dark grey colour, in 
