54 MIMICRY, AND OTHER PROTECTIVE 
lighter foliage, the blue and purple tints in its plumago 
would far sooner betray it. The robin redbreast too, 
although it might be thought that the red on its breast 
made it much easier to be seen, is in reality not at 
all endangered by it, since it generally contrives to 
get among some russet or yellow fading leaves, where 
the red matches very well with the autumn tints, 
and the brown of the rest of the body with the bare 
branches.” 
Reptiles offer us many similar examples. The most 
arboreal lizards, the iguanas, are as green as the leaves 
they feed upon, and the slender whip-snakes are ren- 
dered almost invisible as they glide among the foliage 
by a similar colouration. How difficult it is some- 
times to catch sight of the little green tree-frogs 
sitting on the leaves of a small plant enclosed in a 
glass case in the Zoological Gardens; yet how much 
better concealed must they be among the fresh green 
damp foliage of a marshy forest. There is a North- 
American frog found on lichen-covered rocks and 
walls, which is so coloured as exactly to resemble 
them, and as long as it remains quiet would certainly 
escape detection. Some of the geckos which cling 
motionless on the trunks of trees in the tropics, are 
of such curiously marbled colours as to match exactly 
with the bark they rest upon. 
In every part of the tropics there are tree-snakes 
that twist among boughs and shrubs, or lie coiled up 
on the dense masses of foliage. These are of many 
distinct groups, and comprise both venomous and 
