in their Natural attitudes of Rest. 485 
markings are seen to be rendered vertical by the attitude, 
as in the moths represented in Figs. 1 and 2. 
Among the moths which are usually found at rest upon 
rocks or stone walls the species of the genus Bryophila are 
probably the best known. The well-known PB. perla, Fabr., 
is so common everywhere throughout the country that 
very little need be said of it. The range of variation in 
this moth is not very great, although in a few districts it 
tends to resemble some local peculiarity in the prevailing 
tints of the walls upon which it both feeds as a larva and 
rests as an imago. A typical example is shown in Fig. 4, 
upon an old, lichen-covered, stone wall. The peculiar grey 
lichen-like markings of its fore-wings are seen to blend 
almost perfectly with the surface upon which the moth is 
resting. B. murals, Forst. = glandifera, Hiibn., isa species 
chiefly confined to our southern coasts and presents an 
interesting contrast to B. perla in its great variability, 
ranging, as it does, from a grey through a number of inter- 
mediate shades to a very dark green, This wide range of 
variation may be seen in a single district, as [ have found 
in the locality in which I have chiefly observed it, viz. 
South Devon, where however the darker forms predomi- 
nate. By this great variability the species is much aided 
in the struggle for existence in localities where stone walls 
and rocks are as varied in hue as they are in South Devon. 
Fig. 5 shows one of the darker forms which are extremely 
well concealed on many of the walls. In this particular 
instance the moth was rather more conspicuous than usual. 
Fig. 6 is an example of the yellowish-green form, which 
is less common than the other. It is however equally 
well protected when at rest on walls or rocks covered with 
yellowish-green lichens. It is to be observed that the 
moths of this genus adopt no special orientation in their 
attitudes of rest, a fact which is in correspondence with 
the irregular growth of lichen-masses on stone. 
