VIII 
THE COLOURS OF SPIDERS 
183 
name to Epeira trifolium. The relative uniformity 
of the cephalothorax is perhaps in part associated 
with the uniform thickness of its cuticle. The mark¬ 
ings of the abdomen are, as we shall see later in more 
detail, probably associated with the tendency of the 
epidermal pigment to become aggregated round the 
little pits which indicate the points of attachment of 
the muscles. M'Cook considers that the variation 
in colour and markings which is so marked in the 
abdomens of many spiders, may be due in part to 
variations in the amount of distention in this region 
due to the presence of eggs and so on. 
Dr. M‘Cook’s volumes contain many other interest¬ 
ing observations on the relations of colour to habitat 
in spiders, on instances of so-called mimicry, etc., for 
which reference must be made to the original. There 
are various observations in the literature of the subject 
tending to prove that spiders in some instances can 
vary their tints according to their environment; that 
harmony with the colours of the environment which 
is known as “ protective coloration ” seems also to be 
relatively common. 
