The Problem of Adaptation 7 
color between the organism and its surroundings, and in 
neglecting all others, is, as has been already said, a point to 
be further examined. 
Not only among mammals and birds have many cases of 
protective coloration been described by writers dealing with 
this subject, but in nearly every group of the animal kingdom 
similar cases have been recognized. The green and brown 
color of lizards may protect them, the green color of many 
frogs is supposed to conceal them as they sit amongst the 
plants on the edge of a stream or pond. The gray-brown 
color of the toad has been described as a resemblance to the 
- dry ground, while the brilliant green of several tree-frogs 
conceals them very effectively amongst the leaves. Many 
fishes are brilliantly colored, and it has even been suggested 
that those living amongst corals and sea-anemonies have 
acquired their colors as a protection, but Darwin states that 
they appeared to him very conspicuous even in their highly 
colored environment. 
Amongst insects innumerable cases of adaptive coloration 
have been described. In fact this is the favorite group 
for illustrating the marvels of protective coloration. A few 
examples will here serve our purpose. The oft-cited case 
of the butterfly Ka//zma is, apparently, a striking instance of 
protective resemblance. When at rest the wings are held 
together over the back, as in nearly all butterflies, so that 
only the under surface is exposed. This surface has an 
unquestionably close resemblance to a brown leaf. It is said 
on no less authority than that of Wallace that when this 
_butterfly alights on a bush it is almost impossible to dis- 
tinguish between it and a dead leaf. The special point in 
the resemblance to which attention is most often called is the 
distinct line running obliquely across the wings which looks 
like the midrib of a leaf. Whether the need of such a close 
resemblance to a leaf is requisite for the life of this butterfly, 
we do not know, of course, and so long as we do not have 
