i883.] 
Evolution by Segregation. 
4 g 5 
of mimicry on a quite different principle. He considers that 
inserts and other animals consciously and intentionally seek 
out lairs and places of abode the colouration of which may 
agree with their own. Thus if the fauna of the Sahara is 
of a desert-colour, it is because animals having such a 
colouration have emigrated thither from the southern slopes 
of the Atlas, or from the northern regions of the Soudan, 
and finding themselves in harmony with their new domicile 
have established themselves there permanently. If the 
Ardtic territories have a number of white forms, in agree- 
ment with the snowy colour of their surface, it is not because 
from a former many-coloured fauna all species not white 
have been gradually eliminated, but because white species 
have taken refuge there. The agreement between the colour 
of an animal and that of its locality is therefore dependent 
upon the will of the former. 
In examining this explanation of mimetism we must begin 
by fully admitting that animals are known, especially when 
in danger, to seek hiding-places which agree in colour with 
their own. Such fadts have not unfrequently been observed 
in aquaria, where small Crustacea, Cephalopods, &c., have 
been seen to place themselves with wonderful accuracy on a 
stone or other objedt closely resembling themselves, and 
where any spedtator not forewarned would scarcely detedt 
their presence. In some cases even assumptions of colour 
have been observed, in accordance with that of neighbouring 
objedts. The attitudes of butterflies are sometimes inten- 
tionally — it would seem — deceptive. The “ browns,” when 
resting on the ground with wings eredt, let the upper pair 
sink down between the lower till the spots of the under- 
side are concealed, and then “ heel over ” so as closely to 
resemble a withered leaf resting slightly a-tilt. 
It is perfectly true that animals purposely and knowingly 
have recourse to mimetic stratagems to deceive their prey. 
The tiger and the leopard, in India, are found to imitate 
most closely the whistling cry of certain species of deer, 
which are their favourite prey. But there are points in 
mimetism which Herr Wagner’s hypothesis cannot, as far 
as we see, be fully made to meet. Let us take the case of 
the mimetic bug ( Spiniger luteicornis ) , described and figured 
by our late lamented friend Thomas Belt.* This insedl 
mimics not merely in colour, but in the movements of its 
wings and antennae, a large hornet {Priocnemis ) , and doubt- 
Naturalist in Nicaragua, p. 319. 
