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COLOURS AND COLORATION IN ANIMALS. AUG., 1892. 
In some animals their apatetic colouring can be changed 
to harmonise with that of the environment : thus the tree- 
frog is bright green when among green leaves, dark brown 
when resting on the earth or among brown leaves ; and trout, 
as well as some other fish, are light coloured when swimming 
over a gravelly or sandy bottom, dark over a muddy one. 
This power of “variable resemblance” is possessed also 
by caterpillars when they are changing into the pupal 
condition. Mr. Poulton has shown by a series of remarkable 
investigations that during the last thirty hours of larval life, 
many caterpillars are greatly influenced by surrounding 
colours, so that the pupae which are formed partake of their 
general character. Thus, he found that caterpillars of the 
Small Tortoise-shell butterfly, which had spent the last day or 
so of that stage among dark surroundings, formed dark pupae, 
while the pupae of those “ turning ” among light surroundings 
were light. In nature, dark pupae are found attached to 
dark surfaces, light pupae to light surfaces, and obviously this 
arrangement gives them a better chance of escaping the 
notice of birds. 
In another type of deceptive colouring, the animal 
resembles not the general surroundings but some special 
object which is of no interest either to its enemies or to the 
creatures on which itself preys; in the former case the 
animal escapes attack, in the latter it is able to approach its 
prey with greater chance of seizing it. Very familiar examples 
of the first-mentioned case are the “stick caterpillars” or 
“ loopers,” which are the larvae of those moths called 
Geometrce. They are very common, but are rarely seen, 
because of their perfect resemblance to the twigs of the 
plants on which they feed. Other caterpillars resemble moss 
or bits of lichen. Many butterflies come in this division, as, 
for instance, our own Red Admiral and Tortoise-shells, which 
are very brilliant on the upper surface of their wings, but very 
sombre on the lower; as they rest on plants, the wings are 
folded so that the lower surface only is seen, which, in that 
position, looks not at all unlike a withered leaf. In some 
tropical butterflies of the genus Kallima this resemblance is 
almost perfect, the shape, veining, blotches, and even the 
holes due to larvae being closely represented. There are 
many other examples equally remarkable, such as the Mantis, 
which closely resembles the flower of an orchid. 
The third type of this class of colouring is where one 
animal resembles, or, as it is said, “ mimics ” another, 
thereby obtaining advantages due to the way in which the 
mimicked form is regarded bv other animals. The best 
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